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Crystals, Volume 12, Issue 8 (August 2022) – 167 articles

Cover Story (view full-size image): Density functional theory allows us to study how high concentrations of Co or Cr in nickel-base superalloys influence the solution energy of Al, Ti, Nb, and Ta. For example, Co’s solution energy can be predicted using the nearest-neighbor interaction in Co-rich matrices. This effect is more complicated for Cr, which has a larger ionic radius and changes the magnetic state of the material. Cr-rich matrices exert a magnetic effect on the energy of Co induced by interactions with the other elements due to elastic deformation of the lattice. High contents of Co or Cr thus increase the solvus temperature of the strengthening phase in nickel-base superalloys, in agreement with the literature and thermodynamic calculations. Please check that the intended meaning has been retained. Please check that the intended meaning has been retained. View this paper
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11 pages, 4770 KiB  
Article
Fabrication and Characterization of Lead-Free BNT-6BT Ultrasonic Transducers Designed by an Intelligent Optimization Algorithm
by Junshan Zhang, Jianxin Zhao, Yi Quan, Jingrong He, Yi Li, Zhe Wang, Kun Zheng, Jian Zhuang, Zhishui Jiang, Li Wen and Wei Ren
Crystals 2022, 12(8), 1181; https://doi.org/10.3390/cryst12081181 - 22 Aug 2022
Cited by 2 | Viewed by 1611
Abstract
Lead-free piezoelectric material-based ultrasonic transducers have been researched for several years, but the inefficient properties and design difficulties have troubled lead-free ultrasonic transducers for a long time. To improve the performance and design efficiency of lead-free ultrasonic transducers, in this work, an equivalent [...] Read more.
Lead-free piezoelectric material-based ultrasonic transducers have been researched for several years, but the inefficient properties and design difficulties have troubled lead-free ultrasonic transducers for a long time. To improve the performance and design efficiency of lead-free ultrasonic transducers, in this work, an equivalent circuit model and intelligent optimization algorithm were combined for use in a transducer design. Firstly, 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3(BNT-6BT) lead-free piezoelectric ceramics were prepared and characterized. Then, BNT-6BT ceramics were used to fabricate the ultrasonic transducers. An equivalent circuit model-based software, PiezoCAD, and a genetic algorithm-based back-propagation neural network were used to optimize the design of the transducers. A 3.03 MHz center frequency and 60.3% −6 dB bandwidth of the optimized transducers were achieved, which were consistent with the neural networks optimization results. To verify the application potential of the lead-free transducers, tungsten rods phantom imaging and polystyrene spheres with 300 μm diameter manipulation were completed by the transducers, and the experiment results indicate that the BNT-6BT lead-free transducers have great potential in further biological and biomedical applications. Full article
(This article belongs to the Special Issue Lead-free Ferro-/Piezoelectric Ceramics and Thin Films)
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15 pages, 3713 KiB  
Article
Reappraisal of The Optical Textures of Columnar Phases in Terms of Developable Domain Structures with Relaxed Constraints and a Rationale for The Striated Texture
by John E. Lydon
Crystals 2022, 12(8), 1180; https://doi.org/10.3390/cryst12081180 - 22 Aug 2022
Viewed by 1494
Abstract
Optical textures pictured in the seminal 1974 textbook, The Microscopy of Liquid Crystals, by Norman Hartshorne, have been reappraised. Some of these, which were described by Hartshorne (and many others) as confused focal conics, were of chromonic and discotic phases, which [...] Read more.
Optical textures pictured in the seminal 1974 textbook, The Microscopy of Liquid Crystals, by Norman Hartshorne, have been reappraised. Some of these, which were described by Hartshorne (and many others) as confused focal conics, were of chromonic and discotic phases, which had not been identified at that time—and would now be recognized as developable domain structures of columnar phases. It is suggested that the rigorous constraint of isometry in these is relaxed in regions of the director field under high stress. A rationale for the characteristic striated appearance of columnar textures is proposed, in which the molecular columns are bundled together, forming twisted ropes within the domains. It is also suggested that the regular alternation of opposing domains in M ribbons minimizes the slippage of columns required as the mesophase develops, and an explanation of the characteristic multi-pole appearance of the brushes in the optical textures of columnar structures is proposed. Full article
(This article belongs to the Special Issue State-of-the-Art Liquid Crystals Research in UK)
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11 pages, 3334 KiB  
Article
Fullerene Movement in a Carbon Nanocontainer
by Alexey M. Bubenchikov, Mikhail A. Bubenchikov, Anna S. Chelnokova, Dmitriy V. Mamontov and Alexander V. Lun-Fu
Crystals 2022, 12(8), 1179; https://doi.org/10.3390/cryst12081179 - 22 Aug 2022
Cited by 3 | Viewed by 1171
Abstract
The character of C60 fullerene motion inside a cylindrical carbon nanocontainer with flat graphene covers has been studied. A new trajectory approach to describe the three-dimensional motion of fullerene is presented, based on the use of motion equations for its center of [...] Read more.
The character of C60 fullerene motion inside a cylindrical carbon nanocontainer with flat graphene covers has been studied. A new trajectory approach to describe the three-dimensional motion of fullerene is presented, based on the use of motion equations for its center of mass in the field of van der Waals forces, as well as the rotational motion equations written in the absolute basis. A high-precision computational technology for implementing this approach is described. Calculations have shown the components of the C60 angular velocity change stepwise. This character of the change in rotation is determined by the impacts of the fullerene on the wall of the container. As a result of these impacts, the energy of rotation changes abruptly. Full article
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14 pages, 4083 KiB  
Article
Characterization and Gamma-ray Shielding Performance of Calcinated and Ball-Milled Calcinated Bentonite Clay Nanoparticles
by Fawzy H. Sallem, M. I. Sayyed, Dalal Abdullah Aloraini, Aljawhara H. Almuqrin and K. A. Mahmoud
Crystals 2022, 12(8), 1178; https://doi.org/10.3390/cryst12081178 - 22 Aug 2022
Cited by 4 | Viewed by 1454
Abstract
The current investigation deals with the fabrication of two various composite-based bentonite clay minerals. The characterization and radiation shielding parameters for the two fabricated composites (calcinated and ball-milled calcinated bentonite) were studied. X-ray diffraction was utilized to illustrate the crystalline phase of the [...] Read more.
The current investigation deals with the fabrication of two various composite-based bentonite clay minerals. The characterization and radiation shielding parameters for the two fabricated composites (calcinated and ball-milled calcinated bentonite) were studied. X-ray diffraction was utilized to illustrate the crystalline phase of the fabricated composites. Furthermore, Williamson and Hall’s method was used to determine the grain size of both the calcinated and ball-milled calcinated composites. The particle size, according to the calculation was 39.84 nm, and the strain was 0.216 for the calcinated bentonite, while the particle size of the ball-milled bentonite was 26.96 nm, and the strain was 0.219. In comparison, the transmission electron microscope (TEM) showed that the grain size of the calcinated bentonite was 566.59 nm, and it was 296.21 nm for the ball-milled calcinated bentonite. The density of the fabricated composites varied between 1.60 and 186 g/cm3 for the calcinated bentonite and between 1.83 and 2.075 g/cm3 for the ball-milled calcinated bentonite. Moreover, the radiation shielding capacity of the composites was analyzed. The results show that the gamma-ray attenuation capacity of ball-milled calcinated bentonite is high compared to ordinary calcinated bentonite. These results confirm the effect of particle grain size on optimizing the gamma-ray shielding capacity of the fabricated materials. Full article
(This article belongs to the Section Mineralogical Crystallography and Biomineralization)
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14 pages, 6010 KiB  
Article
Isolation and Characterization of Cellulose Nanofibers from Wheat Straw and Their Application for the Supercapacitor
by Qing Wang, Junying Han, Xin Wang, Yawei Zhao, Li Zhang, Na Liu, Jihong Huang, Dandan Zhai and Ming Hui
Crystals 2022, 12(8), 1177; https://doi.org/10.3390/cryst12081177 - 21 Aug 2022
Viewed by 1553
Abstract
As a by-product of wheat planting, wheat straw is an abundant agricultural residue with the highest cellulose content of all agricultural fibers. Its resourceful utilization contributes to alleviating the environmental problems it caused. In this study, cellulose from wheat straw (WS) is used [...] Read more.
As a by-product of wheat planting, wheat straw is an abundant agricultural residue with the highest cellulose content of all agricultural fibers. Its resourceful utilization contributes to alleviating the environmental problems it caused. In this study, cellulose from wheat straw (WS) is used as a dispersing agent to prepare a novel multi-walled carbon nanotube-modified nickel foam (NF) electrode. The new electrode is investigated for electrochemical properties relevant to supercapacitors. The 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation is chosen to produce cellulose nanofibers (CNF) from wheat straw. The prepared CNF is used to facilitate the uniform dispersion of multi-walled carbon nanotubes (MWCNT) and favor the formation of a stable CNF-CNTs membrane on the nickel foam skeleton. The influence of dispersing materials and content of CNF on the electrochemical performance of electrodes is investigated. It is revealed that the incorporation of CNF can improve the electrochemical stability of electrodes. Moreover, it also exhibits optimum capabilities (70.2% capacitance retention from 1 to 40 mA cm−2) when CNF:MWCNT = 1:0.7. The areal capacity of the CNF-MWCNT/NF electrode for a scanning rate of 5 mV s−1 is twice that of the MWCNT/NF electrode and 30 times that of the NF electrode, indicating it is a promising candidate to ensure the synchronization of a green environment and energy development. Full article
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22 pages, 2737 KiB  
Article
Measurement and Correlation of the Solubility of Florfenicol in Four Binary Solvent Mixtures from T = (278.15 to 318.15) K
by Xinyuan Zhang, Pingping Cui, Qiuxiang Yin and Ling Zhou
Crystals 2022, 12(8), 1176; https://doi.org/10.3390/cryst12081176 - 21 Aug 2022
Cited by 1 | Viewed by 1696
Abstract
Florfenicol is an excellent antibiotic and is widely used in animal bacterial diseases. However, its poor water solubility leads to various problems, such as poor absorption and bioavailability. The development of nanocrystals is one of the most useful methods for solubilizing florfenicol, which [...] Read more.
Florfenicol is an excellent antibiotic and is widely used in animal bacterial diseases. However, its poor water solubility leads to various problems, such as poor absorption and bioavailability. The development of nanocrystals is one of the most useful methods for solubilizing florfenicol, which often requires solubility data of florfenicol in different mixed solvents. In this work, the solubility of florfenicol was determined by the gravimetric method in methanol + water, ethanol + water, 1-propanol + water, and isopropanol + water binary solvents at temperatures from 278.15 to 318.15 K. In these four mixed solvents, the solubility of florfenicol increased with the increase in temperature. The solubility of florfenicol in methanol + water mixed solvent increases with the decrease in water ratio, while the solubility of florfenicol in ethanol + water, 1-propanol + water, or isopropanol + water mixed solvents increased first and then decreased with the decrease in water ratio, indicating a cosolvency phenomenon. The modified Apelblat model, CNIBS/R-K model, Jouyban–Acree model, and NRTL model were used to correlate the solubility data of florfenicol in four binary solvents. RMSD values indicated that the calculated values are in good agreement with the experimental solubility data for all four models, among which the CNIBS/R-K model provides the best correlation. Full article
(This article belongs to the Special Issue Crystallization Process and Simulation Calculation)
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13 pages, 1807 KiB  
Article
Succinyl and Adipoyl Dihydrazones: A Solid-State, Solution and Antibacterial Study
by Edi Topić, Vladimir Damjanović, Katarina Pičuljan, Višnja Vrdoljak and Mirta Rubčić
Crystals 2022, 12(8), 1175; https://doi.org/10.3390/cryst12081175 - 21 Aug 2022
Cited by 1 | Viewed by 1553
Abstract
A series of aryl-functionalized alkyl dihydrazones was prepared by condensation of succinyl or adipoyl dihydrazide and selected ortho-hydroxybenzaldehydes (2-hydroxybenzaldehyde, 2-hydroxy-1-naphthaldehyde, 2,3-dihydroxybenzaldehyde, and 2,4-dihydroxybenzaldehyde) in solution. The obtained products were structurally characterized in the solid state by single-crystal X-ray diffraction (SC-XRD), thermal analysis [...] Read more.
A series of aryl-functionalized alkyl dihydrazones was prepared by condensation of succinyl or adipoyl dihydrazide and selected ortho-hydroxybenzaldehydes (2-hydroxybenzaldehyde, 2-hydroxy-1-naphthaldehyde, 2,3-dihydroxybenzaldehyde, and 2,4-dihydroxybenzaldehyde) in solution. The obtained products were structurally characterized in the solid state by single-crystal X-ray diffraction (SC-XRD), thermal analysis (TGA-DSC), and Fourier transform infrared (FTIR) spectroscopy and in DMSO-d6 solution by nuclear magnetic resonance (NMR) techniques. Combined FTIR and crystal structure data point to a N–NH–C=O tautomeric form of the hydrazone parts as well as the enol-imino tautomeric form of the aldehyde residues and a robust trans-syn conformation for the structurally investigated ones. While the molecules retain the same tautomeric form in the DMSO-d6 solution, they adopt several conformations, due to rotations around Car–C, C–N, and N–N bonds. The compounds show exceptional thermal stability, with a complex degradation pattern. Slight differences in thermal behavior correlate to alkyl chain length and aryl substituents. The in vitro cytotoxic activity of prepared dihydrazones was evaluated on THP-1 and HepG2 cell lines, while their antibacterial activity was tested against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Moraxella catarrhalis bacteria. All compounds proved to be non-cytotoxic, and some exhibited moderate antibacterial activity. Full article
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26 pages, 13161 KiB  
Review
A Review on Mesophase and Physical Properties of Cyclotriphosphazene Derivatives with Schiff Base Linkage
by Zuhair Jamain, Ahmad Nor Asyraf Azman, Nurul Asma Razali and Mohamad Zul Hilmey Makmud
Crystals 2022, 12(8), 1174; https://doi.org/10.3390/cryst12081174 - 21 Aug 2022
Cited by 7 | Viewed by 3754
Abstract
Over the last decades, liquid crystalline has been of great recent importance due to many unique and different features. The linking unit, terminal group, and core system are the most factors to influence the liquid crystal behaviour. Schiff base linkage with the formula [...] Read more.
Over the last decades, liquid crystalline has been of great recent importance due to many unique and different features. The linking unit, terminal group, and core system are the most factors to influence the liquid crystal behaviour. Schiff base linkage with the formula of -C=N- can maintain linearity by providing the stepped core structure with high stability. Incorporation of Schiff base linkage in cyclotriphosphazene system enhances the mesophase characteristic and high thermal stability. This review focussed on the mesophase behaviour and physical properties of cyclotriphosphaze derivatives attached to Schiff base linkages. A basic introduction to liquid crystalline materials, including description and classification, is provided in this review. Full article
(This article belongs to the Special Issue Liquid Crystal Composites)
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11 pages, 8384 KiB  
Article
Design of Semiconductor Contact Grating Terahertz Source with Enhanced Diffraction Efficiency
by Zoltán Tibai, Nelson M. Mbithi, Gábor Almási, József A. Fülöp and János Hebling
Crystals 2022, 12(8), 1173; https://doi.org/10.3390/cryst12081173 - 21 Aug 2022
Cited by 3 | Viewed by 1821
Abstract
We report a semiconductor contact grating terahertz source design based on a rectangular profile for phase-matched terahertz generation in the long infrared pump wavelength range. The calculations show that the best diffraction efficiency can be achieved by a filling factor significantly smaller than [...] Read more.
We report a semiconductor contact grating terahertz source design based on a rectangular profile for phase-matched terahertz generation in the long infrared pump wavelength range. The calculations show that the best diffraction efficiency can be achieved by a filling factor significantly smaller than 50%. Furthermore, the possibility of diffraction efficiency enhancement was investigated by applying three different antireflective coating structures. Numerical simulations have indicated that at 2.06 μm and 3.0 μm pump wavelength, diffraction efficiencies greater than 91% and 89% can be achieved by adding an appropriate antireflective coating to the GaP and GaAs contact grating structure, respectively. In addition, numerical simulations were performed to investigate the influence of wall angles on diffraction efficiency. The results reveal that the wall angle does not significantly affect the diffraction efficiency: while keeping the wall angle deviation from the vertical below 25 degrees, the efficiency drop remains below 5% for otherwise optimal grating parameters. Full article
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8 pages, 3361 KiB  
Article
Effect of Al2O3 on Sintering Reaction of Calcium Ferrite
by Zhenwei Jing, Xiaofei Xing, Hongyan Yan, Ju Meng, Xiwei Qi, Hui Li and Jinglong Liang
Crystals 2022, 12(8), 1172; https://doi.org/10.3390/cryst12081172 - 20 Aug 2022
Viewed by 1155
Abstract
Calcium ferrite containing aluminum (CFA) has been widely used in blast furnace production because it is an important compound that affects the quality of sinter. The influence of Al2O3 on CFA preparation process was studied by the raw material of [...] Read more.
Calcium ferrite containing aluminum (CFA) has been widely used in blast furnace production because it is an important compound that affects the quality of sinter. The influence of Al2O3 on CFA preparation process was studied by the raw material of CaO-Fe2O3-Al2O3. Diffraction of x-rays (XRD), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) analysis were used to analyze the phase, micro morphology and the reducibility of the products. The results showed that CaO tended to combine more with Fe2O3 to form calcium ferrite with the increase of Fe2O3, whereas CaO tended to combine more with Al2O3 to form calcium aluminate with the content of Al2O3 above 45%. The micro morphology of sintered samples had a stable sintering skeleton structure due to the existence of calcium ferrite. Calcium ferrite was distributed between different particles in flakes, whereas calcium aluminate was attached to the Al2O3 particle surface. The large amount of calcium aluminate inhibited the emergence of calcium ferrite, and it had an adverse impact on the reducibility of sinter and the preparation of CFA. Full article
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13 pages, 3992 KiB  
Article
Barium Hydroxide Nanoparticle–Phosphoric Acid System for Desalination and Consolidation of Tomb Murals
by Yan Rong, Jinglong Yang, Siping Huang and Yuhu Li
Crystals 2022, 12(8), 1171; https://doi.org/10.3390/cryst12081171 - 20 Aug 2022
Cited by 1 | Viewed by 1656
Abstract
Tomb murals are an important component of cultural heritage, but the extant majority of burial murals are severely damaged. There are various causes behind the deterioration of tomb murals, among which the detrimental effects of sodium sulfate on murals are some of the [...] Read more.
Tomb murals are an important component of cultural heritage, but the extant majority of burial murals are severely damaged. There are various causes behind the deterioration of tomb murals, among which the detrimental effects of sodium sulfate on murals are some of the most difficult to treat. In the past decades, the application of alkaline earth metal hydroxides (such as Ba(OH)2, Ca(OH)2, and Ma(OH)2) for the conservation and consolidation of murals has become more common. However, there are some problems, such as large particles, poor permeability, and potential for surface whitening. In response to this issue, we investigated a facile method for the synthesis of nano barium hydroxide (N-Ba(OH)2), from which we developed a barium hydroxide nanoparticle–phosphoric acid (N-Ba(OH)2/H3PO4) multisite in situ consolidation system. The results show that N-Ba(OH)2/H3PO4 consolidation material has good permeability and mechanical properties compared with commercial Ba(OH)2 and other common consolidation materials. This material performs very well in both salt resistance and desalination tests, the color difference change is minimal, and the technique is suitable for the practical manipulation of outdoor artifact conservation work. Recently, it has even been used in the desalination and consolidation of tomb murals in Jiangxi, China, the results of which opened a new way of thinking about the long-term conservation of tomb murals. Full article
(This article belongs to the Special Issue Archaeological Crystalline Materials)
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11 pages, 5697 KiB  
Article
A Tunable Zig-Zag Reflective Elastic Metasurface
by Zhu-Long Xu, Shi-Bo Yu, Junjie Liu and Kuo-Chih Chuang
Crystals 2022, 12(8), 1170; https://doi.org/10.3390/cryst12081170 - 20 Aug 2022
Cited by 9 | Viewed by 1875
Abstract
In this paper, inspired by origami structures, we offer a very simple tuning method to overcome the limitations of general elastic metasurfaces, where only a certain functionality at a certain frequency range can be achieved, by designing a reflective metasurface based on foldable/deployable [...] Read more.
In this paper, inspired by origami structures, we offer a very simple tuning method to overcome the limitations of general elastic metasurfaces, where only a certain functionality at a certain frequency range can be achieved, by designing a reflective metasurface based on foldable/deployable zig-zag structures. By utilizing peg/screw connections, the folding angles of the zig-zag structures can be easily tuned while also being fixable. By tuning the folding angle, the subunit of the zig-zag metasurface can cover a 2π phase shift span and the phase shift can be tuned continuously, and almost linearly, with respect to the folding angle. With a simple folding motion, the tunable reflective metasurface can steer reflected flexural waves in different directions and focus-reflected flexural waves with different focal distances. In addition to demonstrating tunable performance, the mechanism that associates the changing speed of the phase shift is explained. The proposed tunable zig-zag elastic metasurface provides a new way to design reconfigurable metamaterials/metasurfaces. Full article
(This article belongs to the Special Issue Active, Tunable and Reconfigurable Elastic Metamaterials)
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10 pages, 2001 KiB  
Article
Optical AR Coatings of the Mid-IR Band for ZnGeP2 Single Crystals Based on ZnS and Oxide Aluminum
by Mikhail Zinoviev, Nikolai Nikolayevich Yudin, Sergey Podzvalov, Elena Slyunko, Nikolai Aleksandrovich Yudin, Maksim Kulesh, Igor Dorofeev and Houssain Baalbaki
Crystals 2022, 12(8), 1169; https://doi.org/10.3390/cryst12081169 - 19 Aug 2022
Cited by 5 | Viewed by 1319
Abstract
In this work, the parameters of antireflection interference coatings based on alternating layers of ZnS/Al2O3 on the laser-induced damage threshold (LIDT) of ZGP crystals under the action of Ho:YAG laser radiation at a wavelength of 2.097 μm were determined. The [...] Read more.
In this work, the parameters of antireflection interference coatings based on alternating layers of ZnS/Al2O3 on the laser-induced damage threshold (LIDT) of ZGP crystals under the action of Ho:YAG laser radiation at a wavelength of 2.097 μm were determined. The coating deposition was carried out using the ion-beam sputtering method. The LIDT of the sample with a coating based on alternating layers ZnS and Al2O3 was equal to WoE = 3.45 J/cm2, and the LIDT of the uncoated sample was equal to WoE = 2.23 J/cm2. An increase in the optical breakdown threshold by ~55% was observed after the deposition of an AR coating based on ZnS and Al2O3 materials. An assumption was made about the absence of local fluctuations in the composition and mechanical stresses in the case of the coated sample, namely that this leads to good adhesion of the multilayer coating to the polished surface of the crystal, and as a result to an increase in the optical breakdown threshold as compared to the uncoated sample due to closure of the dangling chemical bonds and bulk defects emerging on the polished surface. Full article
(This article belongs to the Special Issue Single-Crystalline Composition Materials)
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16 pages, 8378 KiB  
Article
Stress Relaxation during Artificial Aging of an AlSi7Cu0.5Mg Cast Alloy
by René Wang, Dinesh Ram, Bernhard Stauder, Ricardo Fernández Gutiérrez, Elisabetta Gariboldi and Maria Cecilia Poletti
Crystals 2022, 12(8), 1168; https://doi.org/10.3390/cryst12081168 - 19 Aug 2022
Cited by 1 | Viewed by 1616
Abstract
After casting and solidification, Al cast cylinder heads undergo a sequence of heat treatments to achieve the desired material properties. This sequence comprises solution heat treatment (SHT), quenching, and artificial aging. Internal stresses are formed due to temperature gradients in the complex geometry [...] Read more.
After casting and solidification, Al cast cylinder heads undergo a sequence of heat treatments to achieve the desired material properties. This sequence comprises solution heat treatment (SHT), quenching, and artificial aging. Internal stresses are formed due to temperature gradients in the complex geometry of the cylinder heads during quenching from the SHT temperature to room temperature. Especially high tensile stresses can produce damage during service. However, part of these internal stresses relaxes during the aging treatment. This work aims to systematically measure the relaxation of the stresses, as well as to phenomenologically model the amount and rate of relaxation. Cast specimens of AlSi7Cu0.5Mg are heat-treated in a furnace before relaxation in a creep testing machine. SHT and SHT plus aging at 180, 200, and 230 °C for 0 h, 0.5 h, 1 h, 4 h, and 6 h are carried out before testing. The relaxation of the stress at constant temperature and strain over 5 h is recorded at three different testing temperatures (180 °C, 200 °C, and 230 °C). The relaxation process is strongly dependent on the testing temperature: at 180 °C and 200 °C the equilibrium stress was already reached after around 1 h, and at 230 °C the equilibrium was reached after 3.5 h. The initial stress values do not influence the relaxation rate. A phenomenological relaxation model is developed to calculate the stress decrement over time and the equilibrium stress in the AlSi7Cu0.5Mg-alloy. The model allows for calculating the levels of residual stress at any time during artificial aging as a function of the thermal history of the alloy, the relaxation temperature, and the initial stress level. Complete relaxation of the initial stress is not reached within 5 h. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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22 pages, 6026 KiB  
Article
Microstructure and Mechanical Behavior of Cu–Al–Ag Shape Memory Alloys Processed by Accumulative Roll Bonding and Subsequent Annealing
by Parinaz Seifollahzadeh, Morteza Alizadeh, Ábel Szabó, Jenő Gubicza and Moustafa El-Tahawy
Crystals 2022, 12(8), 1167; https://doi.org/10.3390/cryst12081167 - 19 Aug 2022
Cited by 2 | Viewed by 1639
Abstract
Ultrafine-grained Cu/Al/Ag composites were processed by an accumulative roll bonding (ARB) technique from pure copper and aluminum sheets and a silver powder. The Al content was fixed to 11 wt.% while the silver concentration was 1, 2, or 3 in wt.%. The ARB-processed [...] Read more.
Ultrafine-grained Cu/Al/Ag composites were processed by an accumulative roll bonding (ARB) technique from pure copper and aluminum sheets and a silver powder. The Al content was fixed to 11 wt.% while the silver concentration was 1, 2, or 3 in wt.%. The ARB-processed samples were heat treated at different temperatures between 750 and 1050 °C for 60 min and then quenched to room temperature (RT) for producing Cu–Al–Ag alloys. The effect of the addition of different Ag contents and various heat treatment temperatures on the structural evolution was investigated. The ARB-processed samples were composed of Cu and Al layers with high dislocation density and fine grain size (a few microns). During heat treatment of the ARB-processed samples, new intermetallic phases formed. For the lowest Ag content (1 wt.%), the main phase was a brittle simple cubic Al4Cu9, while for higher Ag concentrations (2 and 3 wt.%), the quenched samples contain mainly an orthorhombic β1-AlCu3 martensite phase. The martensite phase consisted of very fine lamellas with a thickness of one micron or less. The heat treatment increased the microhardness and the strength of the samples at RT due to the formation of a fine-grained hard martensite phase. For 2 and 3% Ag, the highest martensite phase content was achieved at 850 and 950 °C, respectively. The annealed and quenched samples exhibited good shape memory behavior at RT. Full article
(This article belongs to the Special Issue Mechanical Properties of Advanced Metallic Materials)
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19 pages, 4046 KiB  
Article
Resonant Tunneling of Electrons and Holes through the InxGa1−xN/GaN Parabolic Quantum Well/LED Structure
by Hind Althib
Crystals 2022, 12(8), 1166; https://doi.org/10.3390/cryst12081166 - 19 Aug 2022
Viewed by 1714
Abstract
Models describing the tunneling of electrons and holes through parabolic InxGa1−xN/GaN quantum well/LED structures with respect to strain were developed. The transmission coefficient, tunneling lifetime, and efficiency of LED structures were evaluated by solving the Schrödinger equation. The effects [...] Read more.
Models describing the tunneling of electrons and holes through parabolic InxGa1−xN/GaN quantum well/LED structures with respect to strain were developed. The transmission coefficient, tunneling lifetime, and efficiency of LED structures were evaluated by solving the Schrödinger equation. The effects of the mole fraction on the structure strain, resonant tunneling and tunneling lifetime, and LH–HH splitting were characterized. The value of LH–HH splitting increased and remained higher than the Fermi energy; therefore, only the HH band was dominant in terms of the valence band properties. The results indicate that an increase in the mole fraction can lead to efficiency droop. Full article
(This article belongs to the Special Issue Preparation and Characterization of Optoelectronic Functional Films)
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7 pages, 2043 KiB  
Article
Pyrolyzed Bacterial Cellulose as the Backbone of the Cathode Catalyst-CoFe2O4 for the Li-O2 Battery
by Xiangjun Wang, Yongqing Chi, Peng Wu and Wen Liu
Crystals 2022, 12(8), 1165; https://doi.org/10.3390/cryst12081165 - 19 Aug 2022
Cited by 1 | Viewed by 1422
Abstract
In this paper, CoFe2O4@pyrolyzed bacterial cellulose (CFO@PBC) nanocomposites were synthesized by a hydrothermal process and an in situ composite technique as the cathode for rechargeable Li-O2 batteries (LOB). CoFe2O4@Ketjenblack (CFO@KB) were prepared in the [...] Read more.
In this paper, CoFe2O4@pyrolyzed bacterial cellulose (CFO@PBC) nanocomposites were synthesized by a hydrothermal process and an in situ composite technique as the cathode for rechargeable Li-O2 batteries (LOB). CoFe2O4@Ketjenblack (CFO@KB) were prepared in the same way as the comparison. The as-prepared materials were characterized by SEM, XRD, and BET. The LOB with CFO@PBC-3 showed a maximum initial discharge capacity of 2660 mAh g−1 (electrode) at the current density of 100 mAg−1, while the mass ratio of CoFe2O4 and pyrolyzed bacterial cellulose was 3. The cyclic voltammetry of the CFO@PBC nanocomposite electrodes was investigated at 0.1 mVs−1 in the voltage window of 2.0–4.5 V. With the limited capacity of 640 mAh g−1 (electrode), the CFO@PBC-3 electrode showed the best cycle stability and higher cutoff voltage of discharging. The pyrolyzed bacterial cellulose, as the fibrous 3D backbone in CFO@PBC nanocomposite electrodes, produced better results than the CFO@KB. Full article
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17 pages, 9540 KiB  
Article
Synthesis of One-Dimensional Titanium Oxide Nanowires for Polyvinylidene Fluoride Membrane Optimization
by Muhammad Arsalan Dilbraiz, Mohsan Nawaz, Mr. Imtiaz, Pervaiz Ahmad, Sirajul Haq, Zia Ur Rehman, Hameed Ullah, Mayeen Uddin Khandaker, Nissren Tamam, Abdelmoneim Sulieman and Majed A. Bajaber
Crystals 2022, 12(8), 1164; https://doi.org/10.3390/cryst12081164 - 19 Aug 2022
Cited by 1 | Viewed by 1726
Abstract
Due to their beneficial characteristics, 1D nanowires have made significant advancements in different realms due to their large surface area, unique surface chemistry, and tunable transport properties. Herein, a comprehensive study of titanium oxide nanowires from titanium (IV) isopropoxide, with the addition of [...] Read more.
Due to their beneficial characteristics, 1D nanowires have made significant advancements in different realms due to their large surface area, unique surface chemistry, and tunable transport properties. Herein, a comprehensive study of titanium oxide nanowires from titanium (IV) isopropoxide, with the addition of CNTs in the polymeric membrane, has been conducted to form crystals. This method is quite proficient for nanowire synthetization, incorporated with CNTs and polymeric membranes. Carbon nanotubes (CNTs) were used to enhance their properties with polymeric polyvinylidene fluoride PVDF membrane. The concentration ratio of titanium oxide in PVDF membrane was 1, 3, 5, 10, and 15%. The development of titanium oxide nanowires at the nano level shaped, as the emulsion electrospinning created 1D nanowires. The use of an additive makes the membrane more conductive. FT-IR, XRD, EDS, and SEM techniques were used for size, surface geometry, crystalline nature, blend membrane, and thin film composition determination. Thermal Gravimetric Analysis (TGA) analysis shows that weight loss with temperature increases at optimum level. Full article
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10 pages, 2126 KiB  
Article
Microstructural and Mechanical Properties of a Heat-Treated EV31A Magnesium Alloy Fabricated Using the Stir-Casting Process
by M. Somasundaram and U. NarendraKumar
Crystals 2022, 12(8), 1163; https://doi.org/10.3390/cryst12081163 - 18 Aug 2022
Cited by 7 | Viewed by 1592
Abstract
This study aims to prepare a stir-cast EV31A magnesium alloy and investigate the effects of the T4 condition (solid solution strengthening) and T6 condition (solid solution strengthening cum age hardening) on the phases, microstructure, mechanical properties, and fractography. The solid solution at 520 [...] Read more.
This study aims to prepare a stir-cast EV31A magnesium alloy and investigate the effects of the T4 condition (solid solution strengthening) and T6 condition (solid solution strengthening cum age hardening) on the phases, microstructure, mechanical properties, and fractography. The solid solution at 520 °C for 8 h allows the Rare-Earth Elements (REE) to dissolve in the Mg matrix, but the solubility is limited by the presence of Zn. This phenomenon is responsible for the T4 heat-treated alloy’s strengthening, which raises the UTS to 212 MPa. The formation of new grains within the grains causes an increase in grain boundaries and dislocations during the T6 heat treatment process, increasing the strength (UTS) of the EV31A alloy to 230 MPa. In all three test conditions, the fractography of tensile samples revealed a cleavage-ductile/mixed mode fracture. As expected, the fine-grained T6 sample exhibited superior strengthening at the expense of ductility. Full article
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10 pages, 2262 KiB  
Article
Effect of Ultrasonic Degassing on Mg-Ca Binary Alloy by Ultrasonic Treatment
by Zheng Jia, Bing Yu and Li Fu
Crystals 2022, 12(8), 1162; https://doi.org/10.3390/cryst12081162 - 18 Aug 2022
Cited by 1 | Viewed by 1326
Abstract
The effect of ultrasonic treatment parameters, including ultrasonic treatment duration, frequency resonance, and treatment temperature, on the degassing of Mg-3.03Ca alloys was investigated. The results indicated that the optimum degassing efficiency could be obtained under the ultrasonic resonant condition. When applying ultrasonic treatment [...] Read more.
The effect of ultrasonic treatment parameters, including ultrasonic treatment duration, frequency resonance, and treatment temperature, on the degassing of Mg-3.03Ca alloys was investigated. The results indicated that the optimum degassing efficiency could be obtained under the ultrasonic resonant condition. When applying ultrasonic treatment for 90 s with 150 W at 700 °C, the minimum hydrogen content and the highest degassing efficiency are obtained, respectively (42.8 cm3/100 g and 27.5%). The ultrasonic treatment can remove the gas from the melt and refine the microstructures. Finally, the mechanism of ultrasonic degassing and refinement was analyzed. Full article
(This article belongs to the Special Issue State-of-the-Art Magnesium Alloys)
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14 pages, 4467 KiB  
Article
Controlling the Polymorphic Outcome of 2,6-Dimethoxybenzoic Acid Crystallization Using Additives
by Aina Semjonova and Agris Bērziņš
Crystals 2022, 12(8), 1161; https://doi.org/10.3390/cryst12081161 - 18 Aug 2022
Cited by 2 | Viewed by 1717
Abstract
In this study, 2,6-dimethoxybenzoic acid (2,6MeOBA) was used as a model substance to investigate the use of additives to control the polymorphic outcome of crystallization. 2,6MeOBA exists as three polymorphs. Two of the 2,6MeOBA polymorphs, I and III, obtained in most of the [...] Read more.
In this study, 2,6-dimethoxybenzoic acid (2,6MeOBA) was used as a model substance to investigate the use of additives to control the polymorphic outcome of crystallization. 2,6MeOBA exists as three polymorphs. Two of the 2,6MeOBA polymorphs, I and III, obtained in most of the crystallization experiments, were characterized by thermal analysis, and their relative thermodynamic stability was determined. Forms I and III are enantiotropically related, where form III is the high-temperature form. Pure form II was very difficult to obtain. Crystallization of 2,6MeOBA was explored under different conditions by performing evaporation and cooling crystallization from different solvents. Surfactants, polymers, and different molecular compounds with diverse possibilities for the formation of intermolecular interactions were tested as additives. The additives facilitating the crystallization of the metastable forms were additionally studied under different crystallization conditions. The effect of additives polyethylene glycol (PEG) and hydroxypropyl cellulose (HPC) on the thermodynamic stability and solvent-mediated phase transition (SMPT) kinetics was evaluated. HPC and PEG showed the potential to favor the formation of form III in crystallization from water. Full article
(This article belongs to the Section Crystal Engineering)
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8 pages, 1698 KiB  
Article
External Electric Field Tailored Spatial Coherence of Random Lasing
by Yaoxing Bian, Hongyu Yuan, Junying Zhao, Dahe Liu, Wenping Gong and Zhaona Wang
Crystals 2022, 12(8), 1160; https://doi.org/10.3390/cryst12081160 - 18 Aug 2022
Cited by 5 | Viewed by 1255
Abstract
In this study, spatial coherence tunable random lasing is proposed by designing a random laser with separate coupling configuration between the gain medium and the scattering part. By using the polymer dispersion liquid crystal (PDLC) film with tunable scattering coefficient for supplying random [...] Read more.
In this study, spatial coherence tunable random lasing is proposed by designing a random laser with separate coupling configuration between the gain medium and the scattering part. By using the polymer dispersion liquid crystal (PDLC) film with tunable scattering coefficient for supplying random scattering feedback and output modification, red, green and blue random lasers are obtained. By applying or removing electric field to manipulate the scattering intensity of the PDLC film, intensity and spatial coherence of these random lasing are then switched between the high or low state. This work demonstrates that controlling the external scattering intensity is an effective method to manipulate the spatial coherence of random lasing. Full article
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15 pages, 564 KiB  
Article
Analysis of Smoluchowski’s Coagulation Equation with Injection
by Eugenya V. Makoveeva, Dmitri V. Alexandrov and Sergei P. Fedotov
Crystals 2022, 12(8), 1159; https://doi.org/10.3390/cryst12081159 - 17 Aug 2022
Cited by 7 | Viewed by 1973
Abstract
The stationary solution of Smoluchowski’s coagulation equation with injection is found analytically with different exponentially decaying source terms. The latter involve a factor in the form of a power law function that plays a decisive role in forming the steady-state particle distribution shape. [...] Read more.
The stationary solution of Smoluchowski’s coagulation equation with injection is found analytically with different exponentially decaying source terms. The latter involve a factor in the form of a power law function that plays a decisive role in forming the steady-state particle distribution shape. An unsteady analytical solution to the coagulation equation is obtained for the exponentially decaying initial distribution without injection. An approximate unsteady solution is constructed by stitching the initial and final (steady-state) distributions. The obtained solutions are in good agreement with experimental data for the distributions of endocytosed low-density lipoproteins. Full article
(This article belongs to the Special Issue Phase Transition in External Fields)
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13 pages, 4314 KiB  
Article
Identification of Novel AXL Kinase Inhibitors Using Ligand-Based Pharmacophore Screening and Molecular Dynamics Simulations
by Lavanya Nagamalla, J. V. Shanmukha Kumar, Mohammed Rafi Shaik, Chintakindi Sanjay, Ali M. Alsamhan, Mohsin Ahmed Kasim and Abdulrahman Alwarthan
Crystals 2022, 12(8), 1158; https://doi.org/10.3390/cryst12081158 - 17 Aug 2022
Viewed by 1599
Abstract
AXL kinase is a promising target in novel drug discovery for cancer. A ligand-based pharmacophore model was generated with the Pharmit web server. Its inbuilt PubChem molecule database was screened and led to 408 candidate molecules. Docking of the AXL kinase active sites [...] Read more.
AXL kinase is a promising target in novel drug discovery for cancer. A ligand-based pharmacophore model was generated with the Pharmit web server. Its inbuilt PubChem molecule database was screened and led to 408 candidate molecules. Docking of the AXL kinase active sites with the identified list of candidate molecules was carried out with Autodock Vina docking software. This resulted in four compounds selected for further investigation. Molecular dynamics simulation of two ligands (PubChem-122421875 and PubChem-78160848) showed considerable binding with AXL kinase. From the MM-PBSA binding free energies investigation, the PubChem-122421875 (G = −179.3 kJ/mol) and PubChem-78160848 (G = −208.3 kJ/mol) ligands had favorable protein-ligand complex stability and binding free energy. Hence, PubChem-122421875 and PubChem-78160848 molecules identified in this work could be a potent starting point for developing novel AXL kinase inhibitor molecules. Full article
(This article belongs to the Special Issue Novel Nanomaterials for Catalytic and Biological Applications)
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10 pages, 2065 KiB  
Article
Computational Investigation of the Stability of Di-p-Tolyl Disulfide “Hidden” and “Conventional” Polymorphs at High Pressures
by Valeriya Yu. Smirnova, Anna A. Iurchenkova and Denis A. Rychkov
Crystals 2022, 12(8), 1157; https://doi.org/10.3390/cryst12081157 - 17 Aug 2022
Cited by 3 | Viewed by 1517
Abstract
The investigation of molecular crystals at high pressure is a sought-after trend in crystallography, pharmaceutics, solid state chemistry, and materials sciences. The di-p-tolyl disulfide (CH3−C6H4−S−)2 system is a bright example of high-pressure polymorphism. It [...] Read more.
The investigation of molecular crystals at high pressure is a sought-after trend in crystallography, pharmaceutics, solid state chemistry, and materials sciences. The di-p-tolyl disulfide (CH3−C6H4−S−)2 system is a bright example of high-pressure polymorphism. It contains “conventional” solid–solid transition and a “hidden” form which may be obtained only from solution at elevated pressure. In this work, we apply force field and periodic DFT computational techniques to evaluate the thermodynamic stability of three di-p-tolyl disulfide polymorphs as a function of pressure. Theoretical pressures and driving forces for polymorphic transitions are defined, showing that the compressibility of the γ phase is the key point for higher stability at elevated pressures. Transition state energies are also estimated for α → β and α → γ transitions from thermodynamic characteristics of crystal structures, not exceeding 5 kJ/mol. The β → γ transition does not occur experimentally in the 0.0–2.8 GPa pressure range because transition state energy is greater than 18 kJ/mol. Relations between free Gibbs energy (in assumption of enthalpy) of phases α, β, and γ, as a function of pressure, are suggested to supplement and refine experimental data. A brief discussion of the computational techniques used for high-pressure phase transitions is provided. Full article
(This article belongs to the Special Issue Pressure-Induced Phase Transformations (Volume II))
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14 pages, 4101 KiB  
Article
Enhanced Photocatalytic Performance of Ag3PO4/Mn-ZnO Nanocomposite for the Degradation of Tetracycline Hydrochloride
by Mir Waqas Alam, Hamida Azam, Nadeem R. Khalid, Sumaira Naeem, Muhammad Khalid Hussain, Amal BaQais, Mohd Farhan, Basma Souayeh, Noushi Zaidi and Kaffayatullah Khan
Crystals 2022, 12(8), 1156; https://doi.org/10.3390/cryst12081156 - 17 Aug 2022
Cited by 18 | Viewed by 1971
Abstract
Using sustainable photocatalysts, photocatalytic degradation has emerged as one of the viable strategies to combat water pollution through eco-friendly and cost-effective means. Visible-light-active Ag3PO4/Mn-ZnO nanocomposite photocatalysts were produced in this study using a simple hydrothermal method and varied concentrations [...] Read more.
Using sustainable photocatalysts, photocatalytic degradation has emerged as one of the viable strategies to combat water pollution through eco-friendly and cost-effective means. Visible-light-active Ag3PO4/Mn-ZnO nanocomposite photocatalysts were produced in this study using a simple hydrothermal method and varied concentrations of Ag3PO4 to Mn-ZnO ranging from 0 to 5 wt percent. X-ray diffraction, scanning electron microcopy, energy-dispersive X-ray, transmission electron microscopy, UV–visible spectroscopy, Fourier transform infra-red spectrophotometer, and photoluminescence spectroscopy were used to examine the structural, morphological, and optical properties of synthesized materials. Visible light was used to test the photocatalytic activity of produced Ag3PO4/Mn-ZnO photocatalysts for the breakdown of tetracycline (TC) hydrochloride. In comparison to the other samples, the 3% Ag3PO4/Mn-ZnO nanocomposite exhibited superior activity as a result of improved visible light absorption and suppressed charge carrier recombination. In addition, this sample demonstrated good stability of TC in an aqueous environment after five consecutive cycles. This research will enhance the scope of photocatalysis for environmental applications. Full article
(This article belongs to the Section Materials for Energy Applications)
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9 pages, 2027 KiB  
Article
Laser Additive Manufacturing of Bulk Silicon Nitride Ceramic: Modeling versus Integral Transform Technique with Experimental Correlation
by Cristian N. Mihailescu, Mihai Oane, Bogdan A. Sava, Andrei C. Popescu, Mihail Elisa, Muhammad Arif Mahmood, Natalia Mihailescu, Ana V. Filip, Sinziana Andreea Anghel, Ion N. Mihailescu and Carmen Ristoscu
Crystals 2022, 12(8), 1155; https://doi.org/10.3390/cryst12081155 - 16 Aug 2022
Viewed by 1404
Abstract
A semi-analytical-numerical solution is theorized to describe the laser additive manufacturing via laser-bulk ceramic interaction modeling. The Fourier heat equation was used to infer the thermal distribution within the ceramic sample. Appropriate boundary conditions, including convection and radiation, were applied to the bulk [...] Read more.
A semi-analytical-numerical solution is theorized to describe the laser additive manufacturing via laser-bulk ceramic interaction modeling. The Fourier heat equation was used to infer the thermal distribution within the ceramic sample. Appropriate boundary conditions, including convection and radiation, were applied to the bulk sample. It was irradiated with a Gaussian spatial continuous mode fiber laser (λ = 1.075 µm) while a Lambert-Beer law was assumed to describe the laser beam absorption. A close correlation between computational predictions versus experimental results was validated in the case of laser additive manufacturing of silicon nitride bulk ceramics. The thermal field value rises but stays confined within the irradiated zone due to heat propagation with an infinite speed, a characteristic of the Fourier heat equation. An inverse correlation was observed between the laser beam scanning speed and thermal distribution intensity. Whenever the laser scanning speed increases, photons interact with and transfer less energy to the sample, resulting in a lower thermal distribution intensity. This model could prove useful for the description and monitoring of low-intensity laser beam-ceramic processing. Full article
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10 pages, 2146 KiB  
Article
Enriching Semantics of Geometry Features and Parameters for Additive Manufacturing Peculiar Structure Based on STEP Standards
by Jinhua Xiao and Yang Lei
Crystals 2022, 12(8), 1154; https://doi.org/10.3390/cryst12081154 - 16 Aug 2022
Cited by 1 | Viewed by 1314
Abstract
Owing to the requirements of the AM system integration and standardization for an AM part structure, the AM features and parameters need to extend their related data entities for better information exchange and sharing based on STEP-NC Part 17 for additive manufacturing. In [...] Read more.
Owing to the requirements of the AM system integration and standardization for an AM part structure, the AM features and parameters need to extend their related data entities for better information exchange and sharing based on STEP-NC Part 17 for additive manufacturing. In this paper, we propose an architecture to transfer the manufacturing layer feature and process parameter information among the CAD/CAPP/CAM systems. We classify the AM layer features into four: general geometry feature, foam structure feature, honeycomb structure feature, and lattice structure feature. These features include detailed parameters and a physical performance that represent specific feature data with related entity definitions and relation descriptions. The process information specifies the optimal process parameters that provide the possibility for optimization data interoperability in various application systems. Based on the concepts of the manufacturing layer feature and process parameters in AM, we simultaneously present the specific STEP/STEP-NC-compliant data model to represent the AM layer feature and process parameter information exchange. Absolutely, we also give the conformance analysis and implementation for each application object and the data entities in the interoperability process. Full article
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13 pages, 4234 KiB  
Article
Eucalyptus globulus Extract-Assisted Fabrication of Copper Oxide/Zinc Oxide Nanocomposite for Photocatalytic Applications
by Muhammad Hafeez, Arooba Ghazal, Jahanzeb Khan, Pervaiz Ahmad, Mayeen Uddin Khandaker, Hamid Osman and Sultan Alamri
Crystals 2022, 12(8), 1153; https://doi.org/10.3390/cryst12081153 - 16 Aug 2022
Cited by 2 | Viewed by 1424
Abstract
In this work, we report the engineering of sub 30 nm nanoparticles of copper oxide (CuO) and Zinc oxide (ZnO) and their nanocomposite, using a green method, to degrade an organic dye (methyl orange) that is responsible for water pollution. The plant extract [...] Read more.
In this work, we report the engineering of sub 30 nm nanoparticles of copper oxide (CuO) and Zinc oxide (ZnO) and their nanocomposite, using a green method, to degrade an organic dye (methyl orange) that is responsible for water pollution. The plant extract of Eucalyptus globulus was used as a capping and stabilizing agent, as it is non-toxic, easy to use, and affordable. The percent purity and composition of the samples were found using Energy Dispersive Spectroscopy (EDS), which confirmed the formation of 75% CuO nanoparticles, 77.81% ZnO nanoparticles, and 77.34% ZnO/CuO nanocomposite in respective samples. Morphological analysis was achieved using Scanning Electron Microscopy (SEM). FTIR investigations revealed that the vibrations of CuO and ZnO nanoparticles and CuO/ZnO nanocomposite were observed at 568 cm−1, 617.9 cm−1, and 475 cm−1, respectively. The bandgap of the synthesized CuO and ZnO nanoparticles, and ZnO/CuO nanocomposite was analyzed using Diffuse Reflectance Spectroscopy (DRS), and found to be 3.36 eV, 1.83 eV, and 1.48 eV, respectively. Best photocatalytic activity confirmed that favorable conditions for the maximum degradation of methyl orange are at pH 12 and 0.02 g of the photocatalyst is required. Full article
(This article belongs to the Topic Advanced Structural Crystals)
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21 pages, 6310 KiB  
Article
Diffusion of Tracer Atoms in Al4Ba Phases Studied Using Perturbed Angular Correlation Spectroscopy
by Randal Newhouse, Samantha Cawthorne, Gary S. Collins and Matthew O. Zacate
Crystals 2022, 12(8), 1152; https://doi.org/10.3390/cryst12081152 - 16 Aug 2022
Cited by 1 | Viewed by 1292
Abstract
The Al4Ba crystal structure is the most common structure among binary intermetallic compounds. It is well suited for accommodating large atoms of group II elements and is often the intermediate phase closest to the terminal phase. It is, therefore, of interest [...] Read more.
The Al4Ba crystal structure is the most common structure among binary intermetallic compounds. It is well suited for accommodating large atoms of group II elements and is often the intermediate phase closest to the terminal phase. It is, therefore, of interest to characterize diffusion properties of compounds with this tetragonal crystal structure. In the present study, 111In perturbed angular correlation spectroscopy was used to study solute site occupation and atom movement in In4Ba, Al4Ba, Al4Eu, Al4Sr, and Ga4Sr. The indium tracer and its daughter cadmium were found to occupy only the two Al-type sublattices in these compounds through detection of nuclear quadrupole interactions with axially symmetric EFGs. Measurements with increasing temperature revealed merging of signals due to dynamical averaging of these interactions as Cd atoms jumped at increasing rates between alternating sublattices. The jump rates were estimated to be between 8 kHz and 2 MHz at about 350 °C for Al4Eu and at about 450 °C for In4Ba and Al4Ba. Fits of spectra using Blume’s stochastic model allowed determination of activation enthalpies for average Cd jump rates between alternating Al sublattices in Al4Sr and Ga4Sr to be 1.16(3) eV and 1.47(3) eV, respectively. This result was used to estimate transverse diffusivities of Cd. Full article
(This article belongs to the Special Issue Radioactive Isotopes Based Materials Characterization)
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