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Volume 12, January

Crystals, Volume 12, Issue 2 (February 2022) – 179 articles

Cover Story (view full-size image): CdTe-based pixel detectors have a narrow point spread, and so, they are ideal for measuring strains using high energy X-ray diffraction. To get good strain data, however, you need very precise pixel positions in order to compute scattering angles. Commercial detectors are produced with modules aligned to more than one pixel, but still not quite perfect compared to fitted peak positions. By looking at smooth powder rings that were recorded after moving the detector around, the module geometry could be measured with 200 nm precision. The results were validated by checking the deviatoric strains in a silicon crystal. These came out at the
2 × 10−5 level, which is a significant improvement compared to previous results from fiber-optic coupled CCD detectors. View this paper
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Article
Effect of Fineness and Heat Treatment on the Pozzolanic Activity of Natural Volcanic Ash for Its Utilization as Supplementary Cementitious Materials
Crystals 2022, 12(2), 302; https://doi.org/10.3390/cryst12020302 - 21 Feb 2022
Cited by 1 | Viewed by 414
Abstract
The aim of this study was to investigate the influence of fineness and heat-treatment on the pozzolanic and engineering properties of volcanic ash. To this end, two different fineness levels of volcanic ash, ultra-fine (VAF) and fine (VA), without and after heat treatment [...] Read more.
The aim of this study was to investigate the influence of fineness and heat-treatment on the pozzolanic and engineering properties of volcanic ash. To this end, two different fineness levels of volcanic ash, ultra-fine (VAF) and fine (VA), without and after heat treatment at different temperatures (VA550, VA650, and VA750), were partially substituted for cement. In addition to the control (100% cement), five binary mortar mixes, each containing 20% of the different types of volcanic ash (VAF and VA; heat-treated and not), were prepared. First, X-ray fluorescence (XRF), X-ray powder diffraction (XRD), particle size analysis, and modified Chappelle tests were used to characterize the material. All mortar mixes were then tested for compressive strength development, water absorption, and apparent porosity. Finally, the microstructure of each of the mixes was evaluated by performing XRD, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) analyses on paste samples at 91 days post-formation. The XRD and Chappelle reactivity results revealed increased pozzolanic reactivity with increasing volcanic ash fineness. In contrast, heat treatment adversely affected the pozzolanic reactivity of the volcanic ash due to the formation of crystalline phases at high temperatures. The mortars containing VAF20 (VAF, no heat, at 20%) showed slightly improved compressive strength (69.6 MPa) than the control (68.1 MPa) and all other binary mixes (66.7, 63.5, 64.2, and 63.9 MPa for VA20, VA20-550, VA20-650, and VA20-750, respectively) at 91 days. The mortar containing VAF20 demonstrated the lowest level of water absorption (9.3%) and apparent porosity (19.1%) of all mixes, including the control. The XRD results for the paste samples show that both VA and VAF showed the least intensity of portlandite phase, as compared to the control and other binary mixes. TGA results also show that binary mixes of VA and VAF have a reduced amount of portlandite, resulting in the densification of the mixes’ microstructures. With the addition of VAF, there is a significant shift in the FTIR band from 980 to 992 cm−1, which causes the formation of additional C–S–H gels that lead to the densification of the paste matrix. These results demonstrate that VAF exhibits high pozzolanic reactivity, making it suitable for use as a natural pozzolan that can partially substitute cement in the production of strong, durable, and environmentally friendly concrete. Full article
(This article belongs to the Special Issue Recent Achievements in Crystal Growth)
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Article
Thermal Deformation Behavior and Interface Microstructure Analysis of 2205/Q345 Hot Compression Composite
Crystals 2022, 12(2), 301; https://doi.org/10.3390/cryst12020301 - 21 Feb 2022
Viewed by 296
Abstract
The high-temperature thermal deformation behavior of a 2205/Q345 specimen at 850–1100 °C and strain rate of 0.01–10 s−1 was systematically studied by the Gleeble-3800 thermal simulator, which provided a theoretical basis for the optimization of a 2205 duplex stainless steel composite plate. [...] Read more.
The high-temperature thermal deformation behavior of a 2205/Q345 specimen at 850–1100 °C and strain rate of 0.01–10 s−1 was systematically studied by the Gleeble-3800 thermal simulator, which provided a theoretical basis for the optimization of a 2205 duplex stainless steel composite plate. It is found that the deformation resistance of 2205 steel was different from that of Q345 steel. Therefore, the Q345 steel deformed first, the degree of deformation was large, the degree of recrystallization occurred, and the grain was isometric and relatively large. The 2205 steel was subsequently deformed, the degree of deformation was relatively small, and the microstructure retained the original rolled and elongated structure. In particular, 2205 and Q345 show a coordinated deformation trend as a whole at 1050 °C and 1–10 s−1. Under the action of shear stress, there are many fine grains at the composite interface. Full article
(This article belongs to the Special Issue Investigation on the Formation and Properties of Steels)
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Article
A Solid-Solid Phase Transformation of Triclabendazole at High Pressures
Crystals 2022, 12(2), 300; https://doi.org/10.3390/cryst12020300 - 21 Feb 2022
Viewed by 312
Abstract
Triclabendazole is an effective medication to treat fascioliasis and paragonimiasis parasitic infections. We implemented a reliable quantum mechanical method which is density functional theory at the level of ωB97XD/6-31G* along with embedded fragments to elucidate stability and phase transition between two forms of [...] Read more.
Triclabendazole is an effective medication to treat fascioliasis and paragonimiasis parasitic infections. We implemented a reliable quantum mechanical method which is density functional theory at the level of ωB97XD/6-31G* along with embedded fragments to elucidate stability and phase transition between two forms of triclabendazole. We calculated crystal structure parameters, volumes, Gibbs free energies, and vibrational spectra of two polymorphic forms of triclabendazole under different pressures and temperatures. We confirmed form I was more stable than form II at atmospheric pressure and room temperature. From high-pressure Gibbs free energy computations, we found a pressure-induced phase transformation between form I (triclinic unit cell) and form II (monoclinic unit cell). The phase transition between forms I and II was found at a pressure and temperature of 5.5 GPa and ≈350 K, respectively. In addition, we also studied the high-pressure polymorphic behavior of two forms of triclabendazole. At the pressure of 5.5 GPa and temperature from ≈350 K to 500 K, form II was more stable than form I. However, at temperatures lower than ≈350 K, form I was more stable than form II. We also studied the effects of pressures on volumes and Raman spectra. To the best of our knowledge, no such research has been conducted to determine the presence of phase transformation between two forms of triclabendazole. This is a case study that can be applied to various polymorphic crystals to study their structures, stabilities, spectra, and phase transformations. This research can assist scientists, chemists, and pharmacologists in selecting the desired polymorph and better drug design. Full article
(This article belongs to the Special Issue Computational and Experimental Approaches in Pharmaceutical Crystals)
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Article
Compositions of Gamma and Gamma Prime Phases in an As-Cast Nickel-Based Single Crystal Superalloy Turbine Blade
Crystals 2022, 12(2), 299; https://doi.org/10.3390/cryst12020299 - 20 Feb 2022
Cited by 1 | Viewed by 432
Abstract
The core and the interdendritic regions of an as-cast nickel based single crystal turbine blade were observed by electron microscopy to understand the microstructural development during an investment casting process. The dendrite core region shows an irregular morphology of gamma prime in gamma [...] Read more.
The core and the interdendritic regions of an as-cast nickel based single crystal turbine blade were observed by electron microscopy to understand the microstructural development during an investment casting process. The dendrite core region shows an irregular morphology of gamma prime in gamma due to a relatively short casting time, which prevented the development of gamma prime expected in a solution heat-treated microstructure. By comparison, the interdendritic region comprises three different regions composed of: several elongated gamma prime particles, relatively tiny and irregular gamma prime, and gamma prime with relatively regular morphology. The chemical analysis of these phases showed that, regardless of the analysis point in the core or the interdendritic region, almost the same compositions were acquired in the regular type of gamma and gamma prime phases. This result suggests that if the gamma prime forms in the gamma matrix, the composition of gamma prime is almost uniform regardless of the region and prevailing general chemical composition. In contrast, the composition of the elongated gamma prime in the interdendritic region was slightly different depending on the analysis point even within the same elongated particle. Full article
(This article belongs to the Topic Single-Crystal Ni-Based Alloys)
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Article
A Comparative Analysis of the Tribological Behavior of Hard Layers Obtained by Three Different Hardened-Surface Processes on the Surface of AISI 4140 Steel
Crystals 2022, 12(2), 298; https://doi.org/10.3390/cryst12020298 - 20 Feb 2022
Viewed by 411
Abstract
This work compares the tribological behavior of surface layers obtained by three different hardening processes. The layers were formed on the surface of AISI 4140 steel by applying three different thermochemical treatments. Wear resistance was evaluated using a standardized tribological machine for abrasive [...] Read more.
This work compares the tribological behavior of surface layers obtained by three different hardening processes. The layers were formed on the surface of AISI 4140 steel by applying three different thermochemical treatments. Wear resistance was evaluated using a standardized tribological machine for abrasive wear, according to the limits established by the ASTM G65 “Standard Test Method for Measuring Abrasion Using Dry Sand/Rubber Wheel Apparatus”. According to the results, the boride layers exhibited the highest wear resistance, as compared to nitrided and carburized layers. In contrast, the carburized layers presented the highest loss of volume. Scanning electron microscopy (SEM) was used to analyze the worn surfaces to examine the wear mechanisms. Abrasive wear was identified in all the samples, as the main abrasive wear mechanism. The mean values of the coefficient of friction (CoF) of the hardened surfaces were 0.39, 0.55, and 0.65 for carburizing, nitriding, and boriding samples, respectively, indicating that the wear process may not always be related to a low CoF. The results suggest that the highest hardness is normally associated with high wear resistance, but the coefficient of friction could be not directly related to the hardness of the materials. Finally, a statistical study demonstrates the random nature of the layers obtained by three different hardening processes. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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Article
A Comparative EPR Study of Non-Substituted and Mg-Substituted Hydroxyapatite Behaviour in Model Media and during Accelerated Ageing
Crystals 2022, 12(2), 297; https://doi.org/10.3390/cryst12020297 - 19 Feb 2022
Viewed by 577
Abstract
To assess the application potential of novel biomaterials, their behaviour in model media and upon sterilization should be investigated, as well as the stability related to their storage conditions. Such data are lacking for Mg-substituted HAP (Mg-HAP). Therefore, the changes in the local [...] Read more.
To assess the application potential of novel biomaterials, their behaviour in model media and upon sterilization should be investigated, as well as the stability related to their storage conditions. Such data are lacking for Mg-substituted HAP (Mg-HAP). Therefore, the changes in the local structure of non-substituted and Mg-HAP after irradiation and immersion in corrected simulated fluid and saline solution for 28 days were followed by electron paramagnetic resonance (EPR) spectroscopy for the first time. To better understand the stability of radical species induced by sterilization, EPR spectra of samples kept for 2 h at temperatures up to 373 K were recorded to provide an insight into the stability of the sample storage conditions by the accelerated aging method. Samples were characterized by PXRD, FTIR, SEM, EDS, AAS and TGA. Results confirmed that irradiation does not induce changes in the composition or the structure of any of the investigated materials. Fading or the complete disappearance of radical signals in the EPR spectra after immersion in both media was accompanied by the disappearance of other phases formed as a minor byproduct in the synthesis of substituted HAP, as confirmed by PXRD and FTIR analysis. Obtained results confirm the great potential of Mg-HAPs for biomedical applications, although closer attention should be given to the processes related to sample storage stability at different temperatures. Full article
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Article
Effective Case Depth and Wear Resistance of Pack Carburized SCM 420 Steel Processed Using Different Concentrations of Natural Shell Waste Powders and Carburizing Duration
Crystals 2022, 12(2), 296; https://doi.org/10.3390/cryst12020296 - 19 Feb 2022
Viewed by 319
Abstract
The efficacy of using coconut shell powder (CSP) and dog conch shell powder (DCSP) as an alternative carburizing media for SCM 420 steel pack carburization was investigated. The effective case depth and wear resistance of quenched specimens prepared using various CSP–DCSP ratios and [...] Read more.
The efficacy of using coconut shell powder (CSP) and dog conch shell powder (DCSP) as an alternative carburizing media for SCM 420 steel pack carburization was investigated. The effective case depth and wear resistance of quenched specimens prepared using various CSP–DCSP ratios and carburizing times were determined and compared. The effective case depth was measured from the microhardness profile obtained using a Vickers hardness testing machine. A CSP–DCSP ratio of 60%:40% and carburization time of 12 h were found to increase the effective case depth of SCM 420 quenched specimens to 2340 µm. The results clearly showed that the effective case depth increased by increasing carburization time and DCSP concentrations from 0% to 40% as a carburizing media and decreased by further increasing DCSP concentrations to 50%. Moreover, the wear resistance of quenched specimens increased approximately two times as DCSP concentrations were increased from 0% to 40% for a carburization time of 12 h. Full article
(This article belongs to the Special Issue Advanced Experimental and Numerical Analysis of Alloys and Compounds)
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Article
Channel Mobility Model of Nano-Node MOSFETs Incorporating Drain-and-Gate Electric Fields
Crystals 2022, 12(2), 295; https://doi.org/10.3390/cryst12020295 - 19 Feb 2022
Cited by 1 | Viewed by 393
Abstract
A novel channel mobility model with two-dimensional (2D) aspect is presented covering the effects of source/drain voltage (VDS) and gate voltage (VGS), and incorporating the drift and diffusion current on the surface channel at the nano-node level, [...] Read more.
A novel channel mobility model with two-dimensional (2D) aspect is presented covering the effects of source/drain voltage (VDS) and gate voltage (VGS), and incorporating the drift and diffusion current on the surface channel at the nano-node level, at the 28-nm node. The effect of the diffusion current is satisfactory to describe the behavior of the drive current in nano-node MOSFETs under the operations of two-dimensional electrical fields. This breakthrough in the model’s establishment opens up the integrity of long-and-short channel devices. By introducing the variables VDS and VGS, the mixed drift and diffusion current model effectively and meaningfully demonstrates the drive current of MOSFETs under the operation of horizontal, vertical, or 2D electrical fields. When comparing the simulated and experimental consequences, the electrical performance is impressive. The error between the simulation and experiment is less than 0.3%, better than the empirical adjustment required to issue a set of drive current models. Full article
(This article belongs to the Special Issue Nano-Semiconductors: Devices and Technology)
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Article
Investigation of the Flow Behavior of Air-Cooling Ti-6Al-4V Alloy after Superplastic Forming
Crystals 2022, 12(2), 294; https://doi.org/10.3390/cryst12020294 - 19 Feb 2022
Cited by 1 | Viewed by 278
Abstract
The flow behavior of Ti-6Al-4V alloy during the air-cooling process after superplastic forming (SPF) has been discussed. In high-temperature constant strain rate tensile tests, the selected temperatures were 930, 900, 800, 700, and 600 °C, and the initial strain rates were 10−2 [...] Read more.
The flow behavior of Ti-6Al-4V alloy during the air-cooling process after superplastic forming (SPF) has been discussed. In high-temperature constant strain rate tensile tests, the selected temperatures were 930, 900, 800, 700, and 600 °C, and the initial strain rates were 10−2, 10−3, and 10−4/s. The optimized deformation temperatures were 800~900 °C and the strain rates were 10−4~10−3/s. Then, the evolutions of activation energy and deformation strain are also discussed, and the effects of dislocation density and deformation activation energy on flow behavior were consistent. In addition, unstable flow is mainly concentrated in the low-temperature and high strain-rate regions, and this is mainly caused by dynamic recrystallization (DRX). After the SPF process, the possibility of material damage gradually increases during the air-cooling process. Full article
(This article belongs to the Topic Superplastic Forming)
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Article
Identification of Heat-Treated Sapphires from Sri Lanka: Evidence from Three-Dimensional Fluorescence Spectroscopy
Crystals 2022, 12(2), 293; https://doi.org/10.3390/cryst12020293 - 19 Feb 2022
Viewed by 312
Abstract
Heat treatment is an important method used to improve the value of sapphires. The identification of heat-treated sapphires is a significant and challenging subject in gemology. In this study, natural sapphire samples from Ratnapura, Sri Lanka, were heated at different temperatures from 900 [...] Read more.
Heat treatment is an important method used to improve the value of sapphires. The identification of heat-treated sapphires is a significant and challenging subject in gemology. In this study, natural sapphire samples from Ratnapura, Sri Lanka, were heated at different temperatures from 900 °C to 1500 °C. Then, the samples were examined by FTIR and three-dimensional fluorescence spectrometry. When excited by 450 nm light, most natural samples emitted a fluorescence band between 540 nm and 560 nm. This fluorescence disappeared after low-temperature heat treatment. Therefore, the presence of fluorescence between 540 nm and 560 nm is evidence of unheated sapphires from Sri Lanka. Almost all of the samples emitted fluorescence centered at 470 nm after high-temperature treatment. Therefore, fluorescence at 470 nm indicates that the sapphires from Sri Lanka were treated at a high temperature. Three-dimensional fluorescence spectroscopy can serve as a method to identify heat-treated sapphires. Full article
(This article belongs to the Special Issue Gem Crystals)
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Article
Mechanical Properties and Buckling of Kagome Graphene under Tension: A Molecular Dynamics Study
Crystals 2022, 12(2), 292; https://doi.org/10.3390/cryst12020292 - 19 Feb 2022
Viewed by 429
Abstract
Kagome graphene is a carbon allotrope similar to graphene, with a single-atom thickness and a co-planar atomic structure. Despite interesting electronic properties, its mechanical behavior is still elusive. We have investigated the tensile properties of Kagome graphene under various strain rates and finite [...] Read more.
Kagome graphene is a carbon allotrope similar to graphene, with a single-atom thickness and a co-planar atomic structure. Despite interesting electronic properties, its mechanical behavior is still elusive. We have investigated the tensile properties of Kagome graphene under various strain rates and finite temperatures using molecular dynamics simulations. The Young’s modulus, ultimate tensile strength, fracture strain, and fracture toughness of the unsupported bulk material were measured as 96 GPa, 43 GPa, 0.05, and 1.9 J m−3, respectively, at room temperature and a strain rate of 109 s−1. Two deformation-stages were observed under tensile loading: normal and wrinkled. Initially, the Kagome graphene system stays in a co-planar structure without wrinkling until the tensile strain reaches 0.04, where it starts to wrinkle, unlike graphene. The wrinkle wavelength and magnitude suggest a very low bending rigidity, and wrinkle formation does not follow a rate predicted by continuum mechanics. Furthermore, the fracture mechanism of wrinkled Kagome graphene is briefly discussed. Full article
(This article belongs to the Special Issue Graphene Mechanics (Volume II))
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Article
Research on EDM Performance of Renewable Dielectrics under Different Electrodes for Machining SKD11
Crystals 2022, 12(2), 291; https://doi.org/10.3390/cryst12020291 - 18 Feb 2022
Cited by 1 | Viewed by 348
Abstract
Electrical discharge machining (EDM) is a non-traditional process, which can cut materials with a high melting point, high hardness, high strength, and low brittleness. However, the kerosene (dielectric of EDM) produces aerosols and toxic gases at high temperatures, which seriously affect the health [...] Read more.
Electrical discharge machining (EDM) is a non-traditional process, which can cut materials with a high melting point, high hardness, high strength, and low brittleness. However, the kerosene (dielectric of EDM) produces aerosols and toxic gases at high temperatures, which seriously affect the health of operators and air quality. This means that it is not conducive to the green manufacturing and sustainable development of EDM. In this study, thereafter, sunflower seed oil (SSO) and kerosene were used as dielectrics of EDM for machine SKD11, and the machining performance of the two dielectrics under different current, duty ratio, pulse duration and electrodes were comparatively analyzed, such as material remove rate (MRR), surface roughness (Ra), energy efficiency per volume (EEV) and exhaust emissions characteristics (EEC). This investigation found that the minimum value of EEV in SSO was 0.3879 kJ/mm3, which was about 25% lower than the minimum value of 0.4849 kJ/mm3 in kerosene. The emission rate of Cu electrode in SSO was 62.017 µg/min, which was lower than that in 78.857 µg/min, decreasing by about 21.36%, in kerosene. In addition, a super depth of field optical micro-scope was subsequently used in the experiments to observe the diameter of the debris. The results indicated that SSO has a larger proportion of debris of more than 35 µm in diameter. Therefore, SSO can be adopted as a substitute for kerosene dielectric to improve the sustainability of electrical discharge machining and realize green manufacturing. Full article
(This article belongs to the Special Issue Non-traditional Machining of Crystal Materials)
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Article
Inhibited Aggregation of Lithium Salt in Spiro-OMeTAD for Perovskite Solar Cells
Crystals 2022, 12(2), 290; https://doi.org/10.3390/cryst12020290 - 18 Feb 2022
Cited by 1 | Viewed by 385
Abstract
High-efficiency and stable hole transport materials (HTMs) play an essential role in high-performance planar perovskite solar cells (PSCs). 2,2,7,7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spirobi-fluorene (Spiro-OMeTAD) is often used as HTMs in perovskite solar cells because of its excellent characteristics, such as energy level matching with perovskite, good film-forming [...] Read more.
High-efficiency and stable hole transport materials (HTMs) play an essential role in high-performance planar perovskite solar cells (PSCs). 2,2,7,7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spirobi-fluorene (Spiro-OMeTAD) is often used as HTMs in perovskite solar cells because of its excellent characteristics, such as energy level matching with perovskite, good film-forming ability, and high solubility. However, the accumulation and hydrolysis of the common additive Li-TFSI in Spiro-OMeTAD can cause voids/pinholes in the hole transport layer (HTL), which reduces the efficiency of the PSCs. In order to improve the functional characteristics of HTMs, in this work, we first used CsI as a dopant to modify the HTL and reduce the voids in the HTL. A small amount of CsI is introduced into Spiro-OMeTAD together with Li-TFSI and 4-tert-butylpyridine (TBP). It is found that CsI and TBP formed a complex, which prevented the rapid evaporation of TBP and eliminated some cracks in Spiro-OMeTAD. Moreover, the uniformly dispersed TBP inhibits the agglomeration of Li-TFSI in Spiro-OMeTAD, so that the effective oxidation reaction between Spiro-OMeTAD and air produces Spiro-OMeTAD+ in the oxidation state, thereby increasing the conductivity and adjusting the HTL energy. Correspondingly, the PCE of the planar PSC of the CsI-modified Spiro-OMeTAD is up to 13.31%. In contrast, the PSC without CsI modification showed a poor PCE of 10.01%. More importantly, the PSC of Spiro-OMeTAD treated with CsI has negligible hysteresis and excellent long-term stability. Our work provides a low-cost, simple, and effective method for improving the performance of hole transport materials and perovskite solar cells. Full article
(This article belongs to the Special Issue Advances of Low-Dimensional Metal Halide Perovskite Materials)
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Article
Enhanced Light Extraction Efficiency and Modulation Bandwidth of Deep-Ultraviolet Light-Emitting Diodes with Al Nanospheres
Crystals 2022, 12(2), 289; https://doi.org/10.3390/cryst12020289 - 18 Feb 2022
Viewed by 347
Abstract
Planar, nanopillar and Al nanosphere structure AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) were numerically investigated via a three-dimensional finite difference time domain (3D FDTD) method. The three types of DUV-LEDs were compared and analyzed in terms of light extraction efficiency (LEE), Purcell factor ( [...] Read more.
Planar, nanopillar and Al nanosphere structure AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) were numerically investigated via a three-dimensional finite difference time domain (3D FDTD) method. The three types of DUV-LEDs were compared and analyzed in terms of light extraction efficiency (LEE), Purcell factor (FP) and modulation bandwidth. The results showed that nanopillar structure DUV-LEDs with optimal nanopillar height, width and spacing can enhance transverse electric (TE)-polarized LEE to 39.7% and transverse magnetic (TM)-polarized LEE to 4.4%. The remarkable improvement was mainly due to the increased scattering effect, decreased absorption of the p-GaN layer and total internal reflection (TIR) effect. After adopting the Al nanospheres, the TE-polarized modulation bandwidth was increased by 71 MHz and the TM-polarized LEE was enhanced approximately 4.3-fold as compared to the nanopillar LED structure, while the Al nanosphere diameter was 120 nm. The reasons for promotion are mainly attributed to the coupling behavior of diploe and localized surface plasmon induced by Al nanospheres. The designed structures provide a meaningful solution for realization of high-efficiency DUV-LEDs. Full article
(This article belongs to the Special Issue Advances in GaN-Based Optoelectronic Materials and Devices)
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Communication
Performance of Silica Fume-Based Geopolymer Grouts for Heritage Masonry Consolidation
Crystals 2022, 12(2), 288; https://doi.org/10.3390/cryst12020288 - 18 Feb 2022
Viewed by 263
Abstract
Despite the increasing number of studies on geopolymer-based materials, a lack of information still prevails concerning the use of geopolymer materials for the consolidation and conservation of the built heritage. Since the introduction of the term “geopolymer” by Davidovits, several studies have pointed [...] Read more.
Despite the increasing number of studies on geopolymer-based materials, a lack of information still prevails concerning the use of geopolymer materials for the consolidation and conservation of the built heritage. Since the introduction of the term “geopolymer” by Davidovits, several studies have pointed out geopolymers as a potential replacement for traditional binders, mainly due to their advantages associated with mechanical properties and low carbon dioxide emissions. The geopolymers (also known as alkali-activated materials or inorganic polymers) are obtained by a chemical process through which precursors rich in silica and alumina interact with an alkaline medium to result in a material with binding properties. The aim of this study is to exploit the potential of geopolymer-based grouts in the consolidation of stone masonry buildings. Grouting or grout injection is a technique used for the consolidation of heritage masonry buildings; it consists of the introduction of a binding agent to fill the internal voids and cracks. An experimental program was carried out to improve knowledge of geopolymer grouts suitable for consolidation purposes. The experimental findings revealed that the silica-fume-based geopolymer grout has a worse performance from a rheological point of view, whereas it showed promising results in terms of mechanical strength when compared to traditional hydraulic-lime-based grout. Full article
(This article belongs to the Special Issue Geopolymer Composites)
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Article
Effect of Gold Nanoparticles on the Crystallization and Optical Properties of Glass in ZnO-MgO-Al2O3-SiO2 System
Crystals 2022, 12(2), 287; https://doi.org/10.3390/cryst12020287 - 18 Feb 2022
Viewed by 432
Abstract
Gold nanoparticles precipitated in transparent glass-ceramics could pave the way for the development of multifunctional materials that are in demand in modern photonics and optics. In this work, we explored the effect of gold nanoparticles on the crystallization, microstructure, and optical properties of [...] Read more.
Gold nanoparticles precipitated in transparent glass-ceramics could pave the way for the development of multifunctional materials that are in demand in modern photonics and optics. In this work, we explored the effect of gold nanoparticles on the crystallization, microstructure, and optical properties of ZnO-MgO-Al2O3-SiO2 glass containing TiO2 and ZrO2 as nucleating agents. X-ray diffraction, transmission electron microscopy, Raman, and optical spectroscopy were used for the study. We showed that gold nanoparticles have no effect on the formation of gahnite nanocrystals during the glass heat treatments, while optical properties of the glass-ceramics are strongly dependent on the gold addition. A computational model was developed to predict optical properties of glass during the crystallization, and the possibility for adjusting the localized surface plasmon resonance band position with the heat treatment temperature was shown. Full article
(This article belongs to the Special Issue Mineralogical Crystallography Volume II)
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Article
Comparative Analysis of Bubbles Behavior in Different Liquids by Laser-Induced Plasma Micromachining Single-Crystal Silicon
Crystals 2022, 12(2), 286; https://doi.org/10.3390/cryst12020286 - 18 Feb 2022
Viewed by 286
Abstract
Laser-induced plasma micromachining (LIPMM) can be used to fabricate high-quality microstructures of hard and brittle materials. The liquid medium of the LIPMM process plays a key role in inducing the plasma and cooling the materials, but the liquid medium is overheated which induces [...] Read more.
Laser-induced plasma micromachining (LIPMM) can be used to fabricate high-quality microstructures of hard and brittle materials. The liquid medium of the LIPMM process plays a key role in inducing the plasma and cooling the materials, but the liquid medium is overheated which induces lots of bubbles to defocus the laser beam and reduce machining stability. In this paper, a comparative investigation on bubble behavior and its effect on the surface integrity of microchannels in three types of liquids and at different depths during LIPMM has been presented. Firstly, the formation mechanism of microbubbles was described. Secondly, a series of experiments were conducted to study the number and maximum diameter of the attached bubbles and the buoyancy movement of floating bubbles in the LIPMM of single-crystal silicon under deionized water, absolute ethyl alcohol, and 5.6 mol/L phosphoric acid solution with a liquid layer depth of 1–5 mm. It was revealed that the number and maximum diameter of attached bubbles in deionized water were the highest due to its high tension. Different from the continuous rising of bubbles at the tail of the microchannels in the other two liquids, microbubbles in 5.6 mol/L phosphoric acid solution with high viscosity rose intermittently, which formed a large area of bubble barrier to seriously affect the laser focus, resulting in a discontinuous microchannel with an unablated segment of 26.31 μm. When the depth of the liquid layer was 4 mm, absolute ethyl alcohol showed the advantages in narrow width (27.15 μm), large depth (16.5 μm), and uniform depth profile of the microchannel by LIPMM. This was because microbubbles in the anhydrous ethanol quickly and explosively spread towards the edge of the laser processing zone to reduce the bubble interference. This research contributes to a better understanding of the behavior and influence of bubbles in different liquid media and depths in LIPMM of single-crystal silicon. Full article
(This article belongs to the Special Issue Non-traditional Machining of Crystal Materials)
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Article
Unconfined Compressive Strength and Splitting Tensile Strength of Lime Soil Modified by Nano Clay and Polypropylene Fiber
Crystals 2022, 12(2), 285; https://doi.org/10.3390/cryst12020285 - 18 Feb 2022
Viewed by 284
Abstract
Here we study the effects of nano clay and polypropylene fiber on the unconfined compression and splitting properties of lime soil. Through a series of unconfined compressive strength (UCS) tests and splitting strength (STS) tests, the mechanical properties of lime soil (LS), nano [...] Read more.
Here we study the effects of nano clay and polypropylene fiber on the unconfined compression and splitting properties of lime soil. Through a series of unconfined compressive strength (UCS) tests and splitting strength (STS) tests, the mechanical properties of lime soil (LS), nano clay modified lime soil (NLS), fiber modified lime soil (FLS), nano clay and fiber composite modified lime soil (NFLS) are analyzed, and the volume calculation formula of each phase in NFLS is deduced. Nano clay content αn, porosity volume η and lime volume LVi as independent variables, and the prediction models of UCS and STS of NFLS were established. Furthermore, the microstructure of LS, NLS, FLS and NFLS was analyzed by scanning electron microscope (SEM). It can be concluded that (1) with the increase in nano clay content, the UCS and STS of LS and FLS gradually increase. With the increase in fiber content, the UCS of LS first increases and then decreases, while the UCS and STS of NLS and STS of LS increase with the increase in fiber content, and the optimal fiber content is 0.75%. (2) UCS and STS of NFLS and η/LVi meet the linear relationship. The empirical formulas of UCS and STS established in this paper have a prediction accuracy of less than 10%. The strength of NFLS can be predicted according to the dry density of the sample and the content of each component material. (3) Nano clay can fill the pores of LS and promote the pozzolanic reaction between lime and soil, while fiber mainly plays a reinforcing role in LS, so as to improve the UCS and STS of LS. In NFLS, nano clay can improve the interfacial properties between fiber and LS, so as to improve its UCS and STS. This study can provide a reference for the modification technology of lime soil. Full article
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Article
Penetration Gain Study of a Tungsten-Fiber/Zr-Based Metallic Glass Matrix Composite
Crystals 2022, 12(2), 284; https://doi.org/10.3390/cryst12020284 - 18 Feb 2022
Viewed by 269
Abstract
A tungsten fiber/Zr-based bulk metallic glass matrix composite (Wf/Zr-MG) is a potential penetrator material. To compare and analyze the penetration behavior of Wf/Zr-MG and a tungsten heavy alloy (WHA), a penetration experiment into the 30CrMnMo homogeneous armor target plate (RHA) is conducted in [...] Read more.
A tungsten fiber/Zr-based bulk metallic glass matrix composite (Wf/Zr-MG) is a potential penetrator material. To compare and analyze the penetration behavior of Wf/Zr-MG and a tungsten heavy alloy (WHA), a penetration experiment into the 30CrMnMo homogeneous armor target plate (RHA) is conducted in the present paper, by using a 37 mm smooth bore artillery with an impact velocity of 1550 ± 40 m/s. Unlike the penetrator made of WHA, the self-sharpening phenomenon was observed in the nose of the Wf/Zr-MG rod. The experimental results indicate that the penetration ability of Wf/Zr-MG rod is approximately 10% higher than that of the WHA rod when the impact velocity is 1550 ± 40 m/s. The combined findings on the microscopic morphology, composition, hardness distribution around the crater, and the macroscopic structure of the penetrator residual show that under this impact velocity, the Wf/Zr-MG material shows amorphous gasification. The Wfs outside the rod shows bending and backflow, resulting in the maintenance of the self-sharpening nose of the penetrator during the penetration process. Moreover, the hardness peak around the crater formed by the Wf/Zr-MG rod is lower, and the penetration crater is straighter, indicating that the Wf/Zr-MG rod has a stronger slag removal ability, lower penetration resistance, and higher penetration efficiency. It is an ideal penetrator material. Full article
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Article
Temperature-Resolved Anisotropic Displacement Parameters from Theory and Experiment: A Case Study
Crystals 2022, 12(2), 283; https://doi.org/10.3390/cryst12020283 - 18 Feb 2022
Viewed by 277
Abstract
Anisotropic displacement parameters (ADPs) for an organopalladium complex were obtained from synchrotron diffraction data between 100 and 250 K and compared to the results from first-principles calculations at the harmonic approximation. Calculations and experiments agree with respect to the orientation of displacement ellipsoids [...] Read more.
Anisotropic displacement parameters (ADPs) for an organopalladium complex were obtained from synchrotron diffraction data between 100 and 250 K and compared to the results from first-principles calculations at the harmonic approximation. Calculations and experiments agree with respect to the orientation of displacement ellipsoids and hence the directionality of atomic movement, but the harmonic approximation underestimates the amplitudes of motion by about 20%. This systematic but modest underestimation can only be reliably detected with a high-quality experimental benchmark at hand. Our experiments comprised diffraction data at 20 K intervals from 130–250 K on the same crystal. An additional high-resolution data set was collected at 100 K on a second crystal and underlined the robustness of our approach with respect to the individual sample, resolution, and instrumentation. In the temperature range relevant for our study and for many diffraction experiments, the discrepancy between experimentally determined and calculated displacement appears as an almost constant temperature offset. The systematic underestimation of harmonic theory can be accounted for by calculating the ADPs for a temperature 20 K higher than that of the actual diffraction. This entirely empirical “+20 K rule” lacks physical relevance but may pave the way for application in larger systems where a more reliable quasi-harmonic approximation remains computationally demanding or even entirely unaffordable. Full article
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Article
Dynamic Simulation and Parameter Analysis of Contact Mechanics for Mimicking Geckos’ Foot Setae Array
Crystals 2022, 12(2), 282; https://doi.org/10.3390/cryst12020282 - 18 Feb 2022
Viewed by 316
Abstract
According to the dynamic characteristics of the adhesion desorption process between gecko-like polyurethane setae and the contact surface, the microcontact principle of an elastic sphere and plane is established based on the Johnson–Kendall–Robert model. On this basis, combined with the cantilever beam model, [...] Read more.
According to the dynamic characteristics of the adhesion desorption process between gecko-like polyurethane setae and the contact surface, the microcontact principle of an elastic sphere and plane is established based on the Johnson–Kendall–Robert model. On this basis, combined with the cantilever beam model, microscale adhesive contact models in the case of a single and an array of setae are obtained. The contact process is numerically simulated and verified by the adhesion desorption test. After that, the effects of external preload, the elastic modulus of setae material, the surface energy, and the surface roughness on the contact force and depth during the dynamic contact process of setae are studied. The results show that the error between the simulation and test is 15.9%, and the simulation model could reflect the real contact procedure. With the increase in preload, the push-off force of the setae array would grow and remain basically constant after reaching saturation. Increasing the elastic modulus of setae material would reduce the contact depth, but have little effect on the maximum push-off force; with the increase in the surface energy of the contact object, both the push-off force between the objects and the contact depth during desorption would increase. With the increase in wall roughness, the push-off force curve of the setae array becomes smoother, but the maximum push-off force would decrease. By exploring the dynamic mechanical characteristics of the micro angle of setae, the corresponding theoretical basis is provided for the numerical simulation of the adsorption force of macro materials. Full article
(This article belongs to the Special Issue Dynamic Behavior of Materials)
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Article
Influence of Non-Metallic Inclusions on Local Deformation and Damage Behavior of Modified 16MnCrS5 Steel
Crystals 2022, 12(2), 281; https://doi.org/10.3390/cryst12020281 - 18 Feb 2022
Cited by 1 | Viewed by 466
Abstract
This work investigates a ferrite matrix with multiple non-metallic inclusions to evaluate their influence on the global and local deformation and damage behavior of modified 16MnCrS5 steel. For this purpose, appropriate specimens are prepared and polished. The EBSD technique is used to record [...] Read more.
This work investigates a ferrite matrix with multiple non-metallic inclusions to evaluate their influence on the global and local deformation and damage behavior of modified 16MnCrS5 steel. For this purpose, appropriate specimens are prepared and polished. The EBSD technique is used to record local phase and orientation data, then analyze and identify the size and type of inclusions present in the material. The EBSD data are then used to run full phase crystal plasticity simulations using DAMASK-calibrated material model parameters. The qualitative and quantitative analysis of these full phase simulations provides a detailed insight into how the distribution of non-metallic inclusions within the ferrite matrix affects the local stress, strain, and damage behavior. In situ tensile tests are carried out on specially prepared miniature dog-bone-shaped notched specimens in ZEISS Gemini 450 scanning electron microscope with a Kammrath and Weiss tensile test stage. By adopting an optimized scheme, tensile tests are carried out, and local images around one large and several small MnS inclusions are taken at incremental strain values. These images are then processed using VEDDAC, a digital image correlation-based microstrain measurement tool. The damage initiation around several inclusions is recorded during the in situ tensile tests, and damage initiation, propagation, and strain localization are analyzed. The experimental results validate the simulation outcomes, providing deeper insight into the experimentally observed trends. Full article
(This article belongs to the Special Issue Applications of Crystal Plasticity in Forming Technologies)
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Article
Grain Knowledge Graph Representation Learning: A New Paradigm for Microstructure-Property Prediction
Crystals 2022, 12(2), 280; https://doi.org/10.3390/cryst12020280 - 18 Feb 2022
Cited by 1 | Viewed by 657
Abstract
The mesoscopic structure significantly affects the properties of polycrystalline materials. Current artificial-based microstructure-performance analyses are expensive and require rich expert knowledge. Recently, some machine learning models have been used to predict the properties of polycrystalline materials. However, they cannot capture the complex interactive [...] Read more.
The mesoscopic structure significantly affects the properties of polycrystalline materials. Current artificial-based microstructure-performance analyses are expensive and require rich expert knowledge. Recently, some machine learning models have been used to predict the properties of polycrystalline materials. However, they cannot capture the complex interactive relationship between the grains in the microstructure, which is a crucial factor affecting the material’s macroscopic properties. Here, we propose a grain knowledge graph representation learning method. First, based on the polycrystalline structure, an advanced digital representation of the knowledge graph is constructed, embedding ingenious knowledge while completely restoring the polycrystalline structure. Then, a heterogeneous grain graph attention model (HGGAT) is proposed to realize the effective high-order feature embedding of the microstructure and to mine the relationship between the structure and the material properties. Through benchmarking with other machine learning methods on magnesium alloy datasets, HGGAT consistently demonstrates superior accuracy on different performance labels. The experiment shows the rationality and validity of the grain knowledge graph representation and the feasibility of this work to predict the material’s structural characteristics. Full article
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Article
Modifying HKUST-1 Crystals for Selective Ethane Adsorption Using Ionic Liquids as Synthesis Media
Crystals 2022, 12(2), 279; https://doi.org/10.3390/cryst12020279 - 18 Feb 2022
Viewed by 416
Abstract
Novel adsorbents for methane and ethane based on HKUST-1 metal-organic framework were synthesized by microwave (MW) assisted technique using ionic liquids (ILs) as synthesis media. It was found that the MW synthesis time remarkably impacts both the product yield and the physico-chemical characteristics [...] Read more.
Novel adsorbents for methane and ethane based on HKUST-1 metal-organic framework were synthesized by microwave (MW) assisted technique using ionic liquids (ILs) as synthesis media. It was found that the MW synthesis time remarkably impacts both the product yield and the physico-chemical characteristics of the produced HKUST-1 material. The crystalline phase purity, crystallite size/dispersion and textural properties of the synthesized HKUST-1 matrices determine their performance in methane and ethane adsorption. Therefore, the HKUST-1 material produced in MW fields for 3 min only shows the highest phase purity and the largest surface area (BET) and porosity, along with a rather small crystallite size (below ~300 nm), demonstrating high methane and ethane adsorption capacity in the pressure range 1–30 atm. Full article
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Article
Two Polynuclear Manganese(II) Complexes Based on Multidentate N-Heterocyclic Aromatic Ligand and V-Shaped Polycarboxylate Ligand: Synthesis, Crystal Structure Analysis and Magnetic Properties
Crystals 2022, 12(2), 278; https://doi.org/10.3390/cryst12020278 - 17 Feb 2022
Viewed by 362
Abstract
The reaction of MnCl2, 2-(5-{6-[5-(Pyrazin-2-yl)-1H-1,2,4-triazol-3-yl]pyridin-2-yl}-1H-1,2,4-triazol-3-yl)pyrazine (H2ptptp), 4,4′-sulfonyldibenzoic acid (H2sdba) or 4-(4-carboxyphenoxy)phthalate acid (H3cpop) and [BMI]Br ionic liquids (BMI = 1-butyl-3-methylimidazolium) gave rise to two complexes, {[Mn4(ptptp)2(sdba)2(H2O)2 [...] Read more.
The reaction of MnCl2, 2-(5-{6-[5-(Pyrazin-2-yl)-1H-1,2,4-triazol-3-yl]pyridin-2-yl}-1H-1,2,4-triazol-3-yl)pyrazine (H2ptptp), 4,4′-sulfonyldibenzoic acid (H2sdba) or 4-(4-carboxyphenoxy)phthalate acid (H3cpop) and [BMI]Br ionic liquids (BMI = 1-butyl-3-methylimidazolium) gave rise to two complexes, {[Mn4(ptptp)2(sdba)2(H2O)2]·2H2O}n (1) and {[Mn3(ptptp)(cpop)Br(H2O)2]·2H2O}n (2). The compounds have been well characterized by elemental analysis, IR spectra, thermogravimetric analysis, as well as single-crystal and powder X-ray diffraction. The structure feature of 1 is that Mn(II) ions in the [Mn6(sdba)2] loops of V-shaped sdba2− ligands are ptptp2− ligands, respectively, and a 2D layer is constructed from sdba2− and ptptp2− ligands. The adjacent 2D layers are connected by O–H⋯N hydrogen bonds to form a 3D supramolecular network. The neighbouring trinuclear Mn(II) clusters in 2 are linked by V-shaped cpop3− ligands to give a 2D layer, which is penetrated by ptptp2− ligands to form self-threading structure. The results of variable-temperature magnetic studies have shown that the magnetic interactions between the Mn(II) ions in 1 and 2 are mainly due to antiferromagnetic coupling. Full article
(This article belongs to the Section Crystal Engineering)
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Article
Experimental Analysis of Wax Micro-Droplet 3D Printing Based on a High-Voltage Electric Field-Driven Jet Deposition Technology
Crystals 2022, 12(2), 277; https://doi.org/10.3390/cryst12020277 - 17 Feb 2022
Viewed by 432
Abstract
High-voltage electric field-driven jet deposition technology is a novel high resolution micro scale 3D printing method. In this paper, a novel micro 3D printing method is proposed to fabricate wax micro-structures. The mechanism of the Taylor cone generation and droplet eject deposition was [...] Read more.
High-voltage electric field-driven jet deposition technology is a novel high resolution micro scale 3D printing method. In this paper, a novel micro 3D printing method is proposed to fabricate wax micro-structures. The mechanism of the Taylor cone generation and droplet eject deposition was analyzed, and a high-voltage electric field-driven jet printing experimental system was developed based on the principle of forming. The effects of process parameters, such as pulse voltages, gas pressures, pulse width, pulse frequency, and movement velocity, on wax printing were investigated. The experimental results show that the increasing of pulse width and duration of pulse high voltage increased at the same pulse frequency, resulting in the micro-droplet diameter being increased. The deposited droplet underwent a process of spreading, shrinking, and solidifying. The local remelting and bonding were acquired between the contact surfaces of the adjacent deposited droplets. According to the experiment results, a horizontal line and a vertical micro-column were fabricated by adjusting the process parameters; their size deviation was controlled within 2%. This research shows that it is feasible to fabricate the micro-scale wax structure using high-voltage electric field-driven jet deposition technology. Full article
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Article
Analysis of the Radiation Attenuation Parameters of Cu2HgI4, Ag2HgI4, and (Cu/Ag/Hg I) Semiconductor Compounds
Crystals 2022, 12(2), 276; https://doi.org/10.3390/cryst12020276 - 17 Feb 2022
Viewed by 385
Abstract
This analysis aims to determine photon attenuation for five different ternary and binary iodide compounds using Phy-X/PSD software. For a broad range of photon energies between 0.015 and 15 MeV, the mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), half-value layer (HVL), tenth-value [...] Read more.
This analysis aims to determine photon attenuation for five different ternary and binary iodide compounds using Phy-X/PSD software. For a broad range of photon energies between 0.015 and 15 MeV, the mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP) for the samples of Cu2HgI4, Ag2HgI4, CuI, AgI, and HgI were calculated. For illustration, the following values of TVL apply at 1 MeV: S1: 6.062 cm, S2: 6.209 cm, S3: 6.929 cm, S4: 6.897 cm, and S5: 4.568 cm. Some important parameters, such as total atomic cross-sections (ACS), electronic cross-sections (ECS), the effective atomic numbers (Zeff), effective electron density (Neff), and effective conductivity (Ceff) of the samples were also calculated. Additionally, exposure buildup factors (EBF) and energy-absorption buildup factor (EABF) were estimated. These data on the radiation characteristics of our samples could be useful for gamma attenuation. The HgI sample has the highest FNRCS values (0.0892) relative to the other tested samples showing good neutron attenuation features. The CuI sample shows low gamma attenuation features; in contrast, it shows high neutron attenuation features. Full article
(This article belongs to the Special Issue Advanced Materials and Devices for Photodetection)
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Article
Improved Solubility and Dissolution Rate of Ketoprofen by the Formation of Multicomponent Crystals with Tromethamine
Crystals 2022, 12(2), 275; https://doi.org/10.3390/cryst12020275 - 17 Feb 2022
Viewed by 454
Abstract
This study aims to improve the dissolution rate of ketoprofen by preparing multicomponent crystals with tromethamine. The multicomponent crystals (equimolar ratio) of ketoprofen and tromethamine were prepared by the solvent co-evaporation method. The solid-state properties of the resulting powder were characterized by powder [...] Read more.
This study aims to improve the dissolution rate of ketoprofen by preparing multicomponent crystals with tromethamine. The multicomponent crystals (equimolar ratio) of ketoprofen and tromethamine were prepared by the solvent co-evaporation method. The solid-state properties of the resulting powder were characterized by powder X-ray diffraction, DSC thermal analysis, FT–IR spectroscopy, solubility, and in vitro dissolution rate. The crystal structure of the multicomponent crystal was determined by single-crystal X-ray diffraction analysis. The results showed that the powder X-ray diffraction pattern of the ketoprofen–tromethamine binary system was different from that of the starting materials. This difference indicates the formation of a new crystalline phase between ketoprofen and tromethamine (equimolar ratio). The DSC thermogram of the ketoprofen–tromethamine binary system exhibited a single and sharp endothermic peak at 128.67 °C, attributed to the melting point of a multicomponent crystal of ketoprofen–tromethamine. A single-crystal X-ray analysis revealed that ketoprofen–tromethamine formed a layered structure, salt-type multicomponent crystal. The solubility and dissolution rate of the multicomponent crystal were notably enhanced compared to the intact ketoprofen. The ketoprofen–tromethamine binary system forms salt-type multicomponent crystals, which can significantly increase the solubility and dissolution rate. Full article
(This article belongs to the Special Issue Computational and Experimental Approaches in Pharmaceutical Crystals)
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Review
Self-Assembled Nanocomposites and Nanostructures for Environmental and Energy Applications
Crystals 2022, 12(2), 274; https://doi.org/10.3390/cryst12020274 - 17 Feb 2022
Viewed by 355
Abstract
Self-assembled nanocomposites are attracting considerable attention owing to their controllable architectures and self-assembly processes, as well as the increase in worldwide environmental effects and energy needs. Further understanding of the self-assembly procedure for improving environmental and energy applications would advance the design and [...] Read more.
Self-assembled nanocomposites are attracting considerable attention owing to their controllable architectures and self-assembly processes, as well as the increase in worldwide environmental effects and energy needs. Further understanding of the self-assembly procedure for improving environmental and energy applications would advance the design and manufacture of nanomaterials for various applications. These materials can be grouped into major categories for various application fields, including powder photocatalysts, membrane photocatalysts, and thin-film thermoelectric nanomaterials. These self-assembled nanomaterials can be used for environmental and energy applications, such as wastewater purification, hydrogen production by water splitting, energy storage, and energy harvesting. In this review, a brief introduction to the definitions and classifications of self-assembled nanocomposites is provided. We aim to provide a summary of the recent research related to self-assembled nanocomposites and nanostructures used for environmental and energy applications. Moreover, typical examples and discussions are aimed at demonstrating the advantages of self-assembled nanostructures. At the end of each section, the structural properties and the application of the nanocomposite or nanostructure are summarized. Finally, we provide perspectives for future research on the design and fabrication of self-assembled nanocomposites and nanostructures. Full article
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Article
Fabrication of Polarization Grating on N-Benzylideneaniline Polymer Liquid Crystal and Control of Diffraction Beam
Crystals 2022, 12(2), 273; https://doi.org/10.3390/cryst12020273 - 17 Feb 2022
Viewed by 314
Abstract
Photoresponsive photoalignable liquid crystalline polymers composed of phenyl benzoate terminated with N-benzylideneaniline were evaluated. These polymers are capable of axis-selective photoreaction, photoinduced orientation, and surface relief grating formation. Polarization holography using an He-Cd laser beam at a wavelength of 325 nm demonstrated [...] Read more.
Photoresponsive photoalignable liquid crystalline polymers composed of phenyl benzoate terminated with N-benzylideneaniline were evaluated. These polymers are capable of axis-selective photoreaction, photoinduced orientation, and surface relief grating formation. Polarization holography using an He-Cd laser beam at a wavelength of 325 nm demonstrated the formation of a surface relief grating with a molecularly oriented structure based on periodic light-induced reorientation and molecular motion. Electrical switching of diffracted light using an electric field response of twisted-nematic cell containing a low-molecular-weight liquid crystal in combination was also demonstrated. Full article
(This article belongs to the Special Issue Liquid Crystal Optics for Applications)
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