Crystals doi: 10.3390/cryst14030283
Authors: Bibhu P. Sahu Mohsen T. Andani Arkajit Ghosh Jian Wang Amit Misra
The crystallography of the eutectic Al-Si microstructure in both unmodified and Sr (0.2 wt.%)-modified hypereutectic Al-20 wt.% Si alloys, processed via arc-melting and laser surface remelting, has been comprehensively characterized using transmission electron microscopy and electron diffraction. Although, under as-cast conditions, specific orientations between different planes of Al and Si, satisfying defined orientation relationships (ORs), have been investigated within the flake morphology, the rapid solidification induced by laser surface remelting results in a notable transformation from a flake morphology to nanocrystalline Si fibers dispersed in an Al matrix. Consequently, this transformation results in a mis-orientation of the interface between the eutectic Al and Si phases, preventing the formation of orientation relationships, thus promoting the formation of faceted interfaces exhibiting substantial lattice disregistry.
]]>Crystals doi: 10.3390/cryst14030282
Authors: Weiqiang Pang Victor Abrukov Darya Anufrieva Dongping Chen
There was an error in the original publication [...]
]]>Crystals doi: 10.3390/cryst14030281
Authors: Emily E. Stumbo Emarald K. Hodge Matthew Williams Diana A. Thornton Colin D. McMillen Jared A. Pienkos
The N-oxide functional group has been exploited for synthetic strategies and drug design, and it has been utilized in imaging agents. Herein, we present rare examples of neutral heteroleptic cyclometallated Ir(III) compounds that contain an uncoordinated N-oxide functional group. These species, along with others described within, were verified by NMR, EA, HRMS, and single-crystal X-ray analysis. N-oxide-containing Ir(III) species were prepared selectively in high yields > 66% from chloro-bridged Ir(III) dimers with Acipimox, a picolinate-type ligand containing the N-oxide functional group. Non-N-oxide analogs were synthesized in a similar fashion (yields > 77%). Electrochemical comparison (cyclic voltammetry) indicates that the presence of an N-oxide functional group anodically shifts the reduction potential, suggesting that the N-oxide is acting as an electron-withdrawing group in these species. Crystallographic studies were pursued to examine the coordination behavior of these N-oxides compared to their non-oxidized congeners. The Ir(III) complexes with Acipimox indeed leave the N-oxide uncoordinated and exposed on the complexes. The uncoordinated N-oxide group is influential in directing the packing structures of these complexes directly through C-H···O and O···π interactions at the N-oxide. The crystallographic characterization of cationic Ir(III) compounds with uncoordinated nitrogen atoms is also presented. The C-H···N interactions between these complexes form a variety of dimers, finite chains, and continuous chains. Future work will focus on functionalizing the cationic Ir(III) species into their corresponding N-oxide derivatives and rigorously characterizing how the N-oxide functional group impacts the optical properties of transition metal compounds in both cationic and neutral complexes.
]]>Crystals doi: 10.3390/cryst14030280
Authors: Yang He Xing Su Kuo Hai
The surface of molybdenum disulfide (MoS2) underwent oxygen plasma treatment to enhance its machinability and mitigate the tearing effects commonly associated with mechanical forces on 2D materials. This treatment led to the oxidation of the atoms on the top 1–3 layers of MoS2, resulting in the formation of MoO3 on the surface. During mechanical scanning probe lithography (m-SPL), only the surface oxide layer was uniformly removed, with material accumulation occurring predominantly on one side of the machined area. The resolution of the machining process was significantly enhanced via dynamic lithography while maintaining atomic-level smoothness in the machined area. Importantly, these techniques only removed the surface oxide layer, preserving the integrity of the underlying MoS2 surface, which was pivotal in avoiding damage to the original material structure. This study provided valuable insights and practical guidance for the nanofabrication of transition metal dichalcogenides (TMDCs) nanodevices, demonstrating a method to finely tune the machining of these materials.
]]>Crystals doi: 10.3390/cryst14030279
Authors: Yang Wu Hao Lan Xiaoming Sun Zihao Hu Yonghui Sun Huifeng Zhang Chuanbing Huang Weigang Zhang
HfO2 has become a promising thermal barrier coating material due to its similarity in structure and chemical properties with ZrO2 and its higher phase structure transition temperature. However, the fracture toughness of HfO2 is not ideal, greatly limiting its application. In this report, we find a special sandwich structure of ceramics, comprising a cubic (C) phase /monoclinic (M) phase/cubic (C) phase. The microstructural evolution and mechanical properties of these ceramics were investigated under annealing at 1500 °C. The results indicate that, with an increase in annealing duration, there was a gradual augmentation in the proportion of the monoclinic (M) phase and the fracture toughness increased from 2.18 MPa·m0.5 to 2.83 MPa·m0.5 after 48 h of annealing, which is higher than many potential TBC materials. The residual compressive stress present in the M phases during the progression of crack propagation served to facilitate the bridging and deflection of cracks. As such, this process led to the alleviation of stress concentration at the crack tip, ultimately enhancing the toughening effect.
]]>Crystals doi: 10.3390/cryst14030278
Authors: Yasukazu Kobayashi Koharu Yamamoto Ryo Shoji
Zinc-included intermetallic compound catalysts of RhZn, PtZn, and PdZn with a molar ration of Zn/metal = 1/1, which are generally prepared using a hydrogen reduction approach, are known to show excellent catalytic performance in some selective hydrogenations of organic compounds. In this study, in order to reduce the incorporated mounts of the expensive noble metals, we attempted to prepare zinc-rich intermetallic compounds via a CaH2-assisted molten salt synthesis method with a stronger reduction capacity than the common hydrogen reduction method. X-ray diffraction results indicated the formation of RhZn13 and Pt3Zn10 in the samples prepared by the reduction of ZnO-supported metal precursors. In a hydrogenation reaction of p-nitrophenol to p-aminophenol, the ZnO-supported RhZn13 and Pt3Zn10 catalysts showed a higher selectivity than the RhZn/ZnO and PtZn/ZnO catalysts with the almost similar conversions. Thus, it was demonstrated that the zinc-rich intermetallic compounds of RhZn13 and Pt3Zn10 could be superior selective hydrogenation catalysts compared to the conventional intermetallic compound catalysts of RhZn and PtZn.
]]>Crystals doi: 10.3390/cryst14030277
Authors: Mattia Lopresti Marco Milanesio Luca Palin
In the original publication [...]
]]>Crystals doi: 10.3390/cryst14030276
Authors: Ki Hyun Nam
Temperature directly influences the function and structure of proteins. Crystal structures determined at room temperature offer more biologically relevant structural information regarding flexibility, rigidity, and thermal motion than those determined by conventional cryocrystallography. Crystal structures can be determined at room temperature using conventional macromolecular crystallography (MX) or serial crystallography (SX) techniques. Among these, MX may theoretically be affected by radiation damage or X-ray heating, potentially resulting in differences between the room temperature structures determined by MX and SX, but this has not been fully elucidated. In this study, the room temperature structure of xylanase GH11 from Thermoanaerobacterium saccharolyticum was determined by MX (RT-TsaGH11-MX). The RT-TsaGH11-MX exhibited both the open and closed conformations of the substrate-binding cleft within the β-sandwich fold. The RT-TsaGH11-MX showed distinct structural changes and molecular flexibility when compared with the RT-TsaGH11 determined via serial synchrotron crystallography. The notable molecular conformation and flexibility of the RT-TsaGH11-MX may be induced by radiation damage and X-ray heating. These findings will broaden our understanding of the potential limitations of room temperature structures determined by MX.
]]>Crystals doi: 10.3390/cryst14030275
Authors: Sangmoon Yoon
Recent advancements in electron detectors and computing power have revolutionized the rapid recording of millions of 2D diffraction patterns across a grid of probe positions, known as four-dimensional scanning transmission electron microscopy (4D-STEM). These datasets serve as the foundation for innovative STEM imaging techniques like integrated center of mass (iCOM) and symmetry STEM (S-STEM). This paper delves into the application of 4D-STEM datasets for diffraction analysis. We therefore use the term scanning electron diffraction (SED) instead of 4D-STEM in this review. We comprehensively explore groundbreaking diffraction methods based on SED, structured into two main segments: (i) utilizing an atomic-scale electron probe and (ii) employing a nanoscale electron probe. Achieving an atomic-scale electron probe necessitates a significant convergence angle (α > 30 mrad), leading to interference between direct and diffracted beams, distinguishing it from its nanoscale counterpart. Additionally, integrating machine learning approaches with SED experiments holds promise in various directions, as discussed in this review. Our aim is to equip materials scientists with valuable insights for characterizing atomic structures using cutting-edge SED techniques.
]]>Crystals doi: 10.3390/cryst14030274
Authors: Jianxian Wen Xiaoyun Song Yanfeng Li Shuwei Liu Yang Yu Wenjun Ye Songxiao Hui
The effect of annealing treatment on the microstructure and texture of a Ti50Ni47Fe3 shape memory alloy tube was studied. The results show that the recrystallization process of a cold-rolled Ti50Ni47Fe3 alloy tube occurs at 600 °C. The microstructure changes from long striped grains to equiaxed recrystallized grains. The main texture of the alloy tube is the fiber texture <111> parallel to RD. With the increase in the annealing temperature, the crystal orientation of the alloy gradually turned to (111)<112>, and a series of secondary textures were distributed along the γ orientation line when the alloy was annealed at a lower temperature (450~600 °C). When the alloy was annealed at 650 °C, the growth of recrystallized grains made the grain orientation change, which led to the weakening of the γ-fiber texture and the formation of recrystallization textures.
]]>Crystals doi: 10.3390/cryst14030273
Authors: Jiansong Zhang Yuzhu Zhang Yue Long Peipei Du Tielei Tian Qianqian Ren
Multi-source ferrous metallurgical dust and sludge are significant components of iron-containing solid waste in the iron and steel industry. It is crucial for the sustainable operation of steel enterprises to recycle iron from ferrous metallurgical dust and sludge (FMDS) for use in steel smelting. However, besides Fe, FMDS also contains valuable elements such as Zn, Pb, K, and Na, among others. While these valuable elements hold high recovery value, they impede the direct reuse of FMDS by iron and steel enterprises. This paper introduces the compositional characteristics of multi-source ferrous metallurgical dust and sludge, analyzes the main recycling technologies associated with FMDS at the present stage of development, and discusses the characteristics of different technologies. In view of this, a new idea of the “cooperative treatment of multi-source ferrous metallurgical dust and sludge—full quantitative recovery of valuable elements” is put forward. This new idea integrates a variety of treatment processes to directly recycle FMDS within the steel plant, enhancing the adequacy of dust and sludge recovery and reducing the risk of environmental pollution. This paper provides a reference for achieving the full quantification and utilization of high-value-added FMDS in steel plants.
]]>Crystals doi: 10.3390/cryst14030272
Authors: Vadym Borysiuk Iakov A. Lyashenko Valentin L. Popov
We report the results of atomistic simulations of friction between two-dimensional titanium carbide Ti2C (MXene) and a silver nanoparticle located on its surface. Numerical experiments were performed within classical molecular dynamics methods using a previously developed scheme for simulations of interactions between MXenes and metal nanoparticles. In the computer experiments performed, both tangential and shear forces were applied to the Ag nanoparticle to initiate its sliding on the surface of the Ti2C MXene. During the simulations, the nanotribological parameters of the studied system, such as the friction force, contact area, friction coefficient, and tangential shear, were computed. It is shown that, for the studied system, the friction coefficient does not depend on the velocity of nanoparticle movement or the contact area. Additionally, the sliding friction of the nanoparticle on the flexible substrate was considered. The latter case is characterized by a larger friction coefficient and contact area due to the formation of wrinkles on the surface of the substrate.
]]>Crystals doi: 10.3390/cryst14030271
Authors: Taehong Park Sunho Lee Dong-Min Kim
As the demand for battery technology with enhanced safety and high energy density increases, solid-state batteries are currently attracting attention as a solution to problems such as fire and explosion risks associated with lithium-ion batteries. In this study, experiments were conducted to synthesize and optimize Li7La3Zr2O12 (LLZO), a solid electrolyte that is a key component of lithium-ion batteries with stability and high energy density. Experimental results showed that sintering at a low temperature of 800 °C for 8 h was the optimal synthesis and sintering time. Additionally, the excess lithium-containing bed powder enabled the production of pure cubic-phase LLZO. Through a sintering process that creates a lithium atmosphere on the bottom surface and facilitates lithium replenishment, an additional tunnel was introduced between the specimen and the alumina powder, allowing the bottom surface of the specimen to be exposed to the lithium atmosphere. By manufacturing a uniform cubic electrolyte, the path to manufacturing all-solid-state batteries was opened. These findings provide a new approach to forming cubic-phase LLZO with much higher ionic conductivity than the tetragonal phase at low sintering temperatures.
]]>Crystals doi: 10.3390/cryst14030270
Authors: Maria Roslova Bernd Büchner Andrey Maljuk
In this review, we summarize recent progress in crystal growth and understanding of the influence of crystal structure on superconductivity in pure and Pb-doped Bi2Sr2CuOy (Bi-2201) materials belonging to the overdoped region of high-temperature cuprate superconductors. The crystal growth of Bi-2201 superconductors faces challenges due to intricate materials chemistry and the lack of knowledge of corresponding phase diagrams. Historically, a crucible-free floating zone method emerged as the most promising growth approach for these materials, resulting in high-quality single crystals. This review outlines the described methods in the literature and the authors’ synthesis endeavors encompassing Pb-doped Bi-2201 crystals, provides a detailed structural characterization of as-grown and post-growth annealed samples, and highlights optimal growth conditions that yield large-size, single-phase, and compositionally homogeneous Bi-2201 single crystals.
]]>Crystals doi: 10.3390/cryst14030269
Authors: Xiangxia Kong Junjun Zhai Ruipeng Ma Fenglian Sun Xuemei Li
Sn58Bi solder is considered a promising lead-free solder that meets the performance requirements, with the advantages of good wettability and low cost. However, the low melting point characteristic of Sn58Bi poses a serious threat to the high-temperature reliability of electronic products. In this study, Sn58Bi solder alloy based on nickel (Ni) functionalization was successfully synthesized, and the effect of a small amount of Ni on creep properties and hardness of Cu/Sn58Bi/Cu micro solder joints at different temperatures (25 °C, 50 °C, 75 °C, 100 °C) was investigated using a nanoindentation method. The results indicate that the nanoindentation depth of micro solder joints exhibits a non-monotonic trend with increasing Ni content at different temperatures, and the slope of the indentation stage curve decreases at 100 °C, showing that the micro solder joints undergo high levels of softening. According to the observation of indentation morphology, Ni doping can reduce the indentation area and accumulation around the indentation, especially at 75 °C and 100 °C. In addition, due to the severe creep phenomenon at 100 °C, the indentation hardness rapidly decreases. The indentation hardness values of micro solder joints of Cu/Sn58Bi/Cu, Cu/Sn58Bi-0.1Ni/Cu, and Cu/Sn58Bi-0.2Ni/Cu at 100 °C are 14.67 ± 2.00 MPa, 21.05 ± 2.00 MPa, and 20.13 ± 2.10 MPa, respectively. Nevertheless, under the same temperature test conditions, the addition of Ni elements can improve the high-temperature creep resistance and hardness of Cu/Sn58Bi/Cu micro solder joints.
]]>Crystals doi: 10.3390/cryst14030268
Authors: Vera M. Kalygina Alexander V. Tsymbalov Petr M. Korusenko Aleksandra V. Koroleva Evgeniy V. Zhizhin
Resistive metal/β-Ga2O3/metal structures with different interelectrode distances and electrode topologies were investigated. The oxide films were deposited by radio-frequency magnetron sputtering of a Ga2O3 (99.999%) target onto an unheated sapphire c-plane substrate (0001) in an Ar/O2 gas mixture. The films are sensitive to ultraviolet radiation with wavelength λ = 254. Structures with interdigital electrode topology have pronounced persistent conductivity. It is shown that the magnitude of responsivity, response time τr, and recovery time τd are determined by the concentration of free holes p involved in recombination processes. For the first time, it is proposed to consider hole trapping both by surface states Nts at the metal/Ga2O3 interface and by traps in the bulk of the film.
]]>Crystals doi: 10.3390/cryst14030267
Authors: Tim Freund Sumbal Jamshaid Milad Monavvar Peter Wellmann
Current research efforts in the field of the semiconducting chalcogenide perovskites are directed towards the fabrication of thin films and subsequently determine their performance in the photovoltaic application. These efforts are motivated by the outstanding properties of this class of materials in terms of stability, high absorption coefficient near the band edge and no significant health concerns compared to their halide counterparts. The approach followed here is to use stacked precursor layers and is adopted from other chalcogenide photovoltaic materials like the kesterites and chalcopyrites. The successful synthesis of BaZrS3 from stacked layers of BaS and Zr and annealing at high temperatures (~1100 °C) with the addition of elemental sulfur is demonstrated. However, the film shows the presence of secondary phases and a flawed surface. As an alternative to this, BaS3 could be used as precursor due to its low melting point of 554 °C. Previously, the fabrication of BaS3 films was demonstrated, but in order to utilize them in the fabrication of BaZrS3 thin films, their microstructure and processing are further improved in this work by reducing the synthesis temperature to 300 °C, resulting in a smoother surface. This work lays the groundwork for future research in the fabrication of chalcogenide perovskites utilizing stacked layers and BaS3.
]]>Crystals doi: 10.3390/cryst14030266
Authors: Saima Hafeez Jianguo Yu Fahim Aziz Umrani Wang Yun Muhammad Ishfaq
Multifunctional integrated meta-devices are the demand of modern communication systems and are given a lot of attention nowadays. Most of the research has focused on either cross-polarization conversion (CPC) or linear-to-circular (LP–CP) conversion. However, simultaneously realizing multiple bands with good conversion efficiency remains crucial. This paper proposes a multiband and multifunctional dual reflective polarization converter surface capable of converting a linearly polarized (LP) wave into a circularly polarized (CP) wave, in frequency bands of 12.29–12.63 GHz, 16.08–24.16 GHz, 27.82–32.21 GHz, 33.75–38.74 GHz, and 39.70–39.79 GHz, with 3 dB axial ratio bandwidths of 2.7%, 40.15%, 14.6%, 13.76%, and 0.2%, respectively. Moreover, the converter is capable of achieving CPC with a polarization conversion ratio (PCR) that exceeds 95%, within the frequency ranges of 13.10–14.72 GHz, 25.43–26.00, 32.46–32.56 GHz, and 39.14–39.59 GHz. In addition, to identify the fundamental cause of the CPC and LP–CP conversion, a comprehensive theoretical investigation is provided. Furthermore, the surface current distribution patterns at different frequencies are investigated to analyze the conversion phenomena. A sample prototype consisting of 20 × 20 unit cells was fabricated and measured, verifying our design and the simulated results. The proposed structure has potential applications in satellite communications, radar, stealth technologies, and reflector antennas.
]]>Crystals doi: 10.3390/cryst14030265
Authors: Yuhan Wang Qing He Zhi Xie
Primary dendrite information is one of the most important metrics to measure the quality of continuous cast slabs. The contrast of low magnification images is very low under the influence of illumination and sampling devices, so the traditional dendrite detection method has the problem of missed detections. We propose an automatic dendrite detection method based on an improved Hough transform, which effectively improves the accuracy and efficiency of primary dendrite detection. By using the local grayscale features of the image, a genetic algorithm-based local contrast enhancement algorithm is proposed. Compared with the traditional contrast enhancement algorithm, it can retain all the information of the dendrites. Combined with the image binarization method based on Hessian matrix, we can obtain more detailed information about the dendrites. According to the continuity and solidification characteristics of dendrites, the Hough transform is improved to extract dendrite information, which effectively reduces the computational cost of the Hough transform. The experimental results show that the method of this paper has versatility, and the error is four pixels compared with the manual method, which can provide a reliable basis for the subsequent judgement of the quality of cast billets.
]]>Crystals doi: 10.3390/cryst14030264
Authors: Maarten R. van Delft Sergio Pezzini Markus König Paul Tinnemans Nigel E. Hussey Steffen Wiedmann
In the original publication [...]
]]>Crystals doi: 10.3390/cryst14030263
Authors: Jáchym Lis Jakub Skočdopole Petr Jaroš Jiří Čapek Karel Trojan Martin Dráb Monika Kučeráková Stanislav Vratislav Ladislav Kalvoda
Investigation of high-entropy alloys in form of bulk samples as well as thin films is currently one of the fastest growing areas in the study of metal alloys. In this paper, a bulk sample of FeNiCoCuCr high-entropy alloy ingot with equimolar composition is prepared by the laboratory arc melting method under an argon atmosphere and used as a source target for deposition of thin films on Si (111) single-crystalline substrates using a novel ionized jet deposition method. The morphology, chemical composition, and real crystalline structure of the target and the prepared layers were characterized by scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, and X-ray and neutron diffraction methods. Transfer coefficients characterizing the mass transport between the target and the grown film were calculated for each of the constituting metallic elements as the ratio of the atomic concentration found in the prepared film divided by its concentration in the deposition target. The dependence of the obtained transfer coefficients on the IJD acceleration voltage is discussed with respect to the main physical and geometric parameters of the deposition process, and their correlations with the cohesive energy of the elements forming the HEA are proposed.
]]>Crystals doi: 10.3390/cryst14030262
Authors: Christopher Hale Zhigang Xu Svitlana Fialkova Jessica Rawles Jagannathan Sankar
Magnesium-based alloys show significant promise for widespread applications owing to their lightweight nature and improved mechanical properties achieved through grain refinement via hot rolling. This investigation focuses on Mg-xAl-yCa-zMn (AXM alloys), pre-heated to temperatures of 350, 400, and 450 °C and processed via both single-pass differential speed rolling (DSR) and conventional rolling (CR). The key findings reveal the interplay between processing temperature, strain rate during single-pass rolling, and an innovative approach for incorporating varying amounts of Ca, influencing grain size, quantity of dynamic recrystallization (DRX) grains, and overall mechanical properties, including strength and ductility. A noteworthy observation is the positive correlation between an increase in the total reduction during hot rolling and a higher fraction of DRXed grains. This leads to a significant reduction in average grain size, diminishing from 60.3 ± 54.3 μm to 19.5 ± 14.2 μm at 40%, nearly a third the size of T4 grains (the initial homogenized microstructure of the AXM alloys). The resultant material strength experiences a doubling from an average of 125 ± 10.2 MPa (T4) to 260 ± 25.8 MPa (DSR rolled at 40%) for the AXM alloys with potential improvement in the ductility depending on rolling speed conditions. This study also aims to analyze the combination of rolling temperature, rolling speed, thickness reduction, speed difference and Ca content implemented across a wide range of temperatures and strain rates to provide a holistic approach to the processing parameters affecting the microstructure and mechanical properties of AXM alloys. Furthermore, this study provides a deeper understanding of DRX mechanisms, including continuous DRX (CDRX), discontinuous DRX (DDRX), and twinning induced DRX (TDRX), while each of these mechanisms plays a distinct role in the overall enhancement of formability and performance of magnesium alloys.
]]>Crystals doi: 10.3390/cryst14030261
Authors: Vediyappan Thirumal Palanisamy Rajkumar Jin-Ho Kim Bathula Babu Kisoo Yoo
A heightened interest in developing MXene (Ti3C2Tx) for energy storage is evident in binder-free MXene ink being directly applied to current collector Ni-foam. Moreover, 2D titanium carbide MXene, with a few layers of nanostructure, has been prepared for symmetric supercapacitor device applications. As-prepared MXene nanosheets exist in two forms: dried powder and ink, achieved through wet-chemical etching and dimethyl sulfoxide delamination from the MAX (Ti3AlC2) phase. This comparative study of electrode devices involves (i) MX-dry powder with binder/additive electrodes and (ii) binder-free MXene inks with directly applied MX-conductive inks. The surface morphological images of pure MX-powder/ink display few layers, and material analysis reveals the good crystalline nature of delaminated MXene (Ti3C2Tx) inks. The electrochemical symmetric supercapacitor device performances of pure MXene powder and binder-free directly applied/coated MXene (Ti3C2Tx) ink, in terms of cyclic voltammetry (CV) and impedance spectroscopy (EIS), exhibit galvanostatic charge–discharge (GCD) curves that show high specific capacitance (Csp) at 105.75 F/g at a current density of 1 A/g. A comparison of active material electrodes demonstrated excellent cycle stability. Hence, in this work, we confirmed the superior capacitive behavior of binder-free MXene ink (MX-I) compared to conductive additives with polymeric binders included in MXene electrodes.
]]>Crystals doi: 10.3390/cryst14030260
Authors: Iñigo Santos-Pereda Virginia Madina Elena Rodriguez Jean-Baptiste Jorcin Esther Acha
In the present work, we studied whether the exposure of synthetic seawater with anaerobic sulphate-reducing bacteria (SRB) on some steel samples generates a bacterial biofilm in their surfaces. Bare steel belonging to a mooring chain as well as two coating systems applied on the steel surface were studied: polyurethane (PU) and thermally sprayed aluminium (TSA) with and without an epoxy-based sealant. After 30 days of immersion in SRB-inoculated synthetic seawater, a bacterial count was attained, and the samples were observed using scanning electron microscopy (SEM) and locally analysed using X-ray scattered energy spectroscopy (EDS). A biofilm developed on every tested surface (continuous or in the form of pustules), with evidence of metabolic activity of the SRB. Finally, a mechanism of degradation for TSA in the presence of SRB is proposed for environments with a high concentration of bacteria.
]]>Crystals doi: 10.3390/cryst14030259
Authors: Guillaume Bastien Cécile Mézière Patrick Batail Denis Gindre
We present a novel approach to second harmonic microscopy combining variable temperature and photon counting. This innovative method aims to generate Second Harmonic Generation (SHG) images by scanning the same area multiple times with short pixel dwell times and low excitation intensities, as illustrated by imaging the full extent of a single crystalline rod of (1,4-bis((4′-(iodoethynyl)phenyl) ethynyl) bicyclo[2.2.2]octane (BCO). Remarkably, this new technique records the change in SHG intensity that occurs along with the crystalline phase transition at 108 K, thereby showing great promise in exploring the intricate instabilities of rotator dynamics concealed within the phase diagrams of molecular machines. Notably, our findings reveal a sustained decrease in non-linear optical intensity as the temperature drops to 95 K, followed by a sharp increase in SHG intensity at approximately 108 K, in synchronicity with the phase transition reported earlier that involves an intricate set of concerted changes in rotor dynamics.
]]>Crystals doi: 10.3390/cryst14030258
Authors: Yanjie Huang Kanghua Chang Jie Yao Xueyong Guo Chen Shen Shi Yan
To enhance both the mechanical properties of hydroxyl-terminated polybutadiene (HTPB) binder and the combustion efficiency of aluminized propellants, 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (OFHD) was employed as a chain extender to impart mechanical regulation to the HTPB binder. Mechanical testing showed that the mechanical properties of fluoride-modified HTPB polyurethane (FPU) were significantly improved: the peak tensile strength of the optimized samples reached 1.99 MPa, and the elongation at break attained 486%. The structural characterization of the FPUs was conducted using Fourier transform infrared (FTIR) spectroscopy. Thermogravimetry-mass spectrometer (TG-MS) analysis revealed that the initial thermal decomposition temperature of the FPU shifted from 170 °C to 162 °C, accompanied by the release of fluorine-containing fragments during decomposition. Analysis of the combustion residue indicated that the addition of OFHD can reduce the agglomeration of aluminum (Al) powder in aluminized propellants. Dynamic pressure characteristics results showed an augmented pressurization rate under argon and oxygen atmospheres, increased by 18.67% and 37.29%, respectively. Heat release tests indicated that the aluminized propellants with the addition of OFHD had a higher combustion heat, being increased by 6.57%. The binder system is expected to be applied in aluminized propellants to improve the mechanical properties and combustion efficiency of Al powder.
]]>Crystals doi: 10.3390/cryst14030257
Authors: Justyna Baranowska Łukasz Szeleszczuk
Novel antiepileptic drugs have been developed at an unparalleled rate during the past 15 years. Gabapentin (GBP), which was approved for the treatment of refractory localization-related epilepsies in the U.K. and Europe in 1993, was one of the first drugs to come out of this era. Since then, GBP has become well-known across the world, not only for its antiepileptic qualities but also for its effectiveness in the treatment of chronic pain disorders, particularly neuropathic pain. In this review, the crystal structures of GBP and GBP-related compounds have been analyzed and compared. Particular attention has been paid to the polymorphism of GBP and its hydrates, their thermodynamic stability, and conformational differences. In addition, the puckering parameters for the cyclohexane ring of a total of 118 molecules of GBP found in the analyzed crystal structures have been calculated and analyzed. The results of recent high-pressure crystallization studies and quantum chemical calculations indicate that the entire landscape of GBP has not been revealed yet.
]]>Crystals doi: 10.3390/cryst14030256
Authors: Michael J. Campbell Daniel A. Decato Chun Li Matthew J. Weaver Nicholas R. Natale
In pursuit of unsymmetrical precursors for the novel series of anthracenyl-isoxazole amide (AIM) antitumor agents, a series of substituted anthracenes were subjected to bromination and re-aromatization in our study, during which we solved four single crystal X-ray diffractometry (Sc-xrd) structures which we report herein. The C-9 nitrile oxide, after its reaction with bromine, was isolated, but when subjected to re-aromatization, it returned to the starting 10-bromo nitrile oxide 1, which did provide an accurate crystal structure, with R = 0.018. The 10-halogenated 3-(9’-anthryl)-isoxazole esters were subjected to bromination and re-aromatization. Surprisingly, the yields obtained in the presence of the isoxazole were reasonably good (62–68% isolated yields), and the major diastereomers allowed for the characterization using Sc-xrd. The penta bromo product 2 showed a trans, trans, cis relationship for the four bromines on the A-ring of the anthracene, and we observed that for the unit cell, the atropisomers displayed a 1:1 ratio at the chiral axis between the isoxazole and anthrancene rings. Similarly, the 10-chloro 3 indicated a ratio of 1:1 at the chiral axis in the crystal structure. A base-induced re-aromatization afforded 3,10-dihalogenated analogues selectively in very good yields (X = Cl, 89%; X = Br 92%), of which the dibromo 4 was characterized using Sc-xrd. The improved yields of the unique diastereomeric bromination products suggested the consideration of a novel electrophilic aromatic substitution mechanism driven by the stereo-electronic environment, imposed by the isoxazole ester substituent. The promise of the application of this chemistry in the future development of AIM antitumor agents is suggested.
]]>Crystals doi: 10.3390/cryst14030255
Authors: Akiko Hori Reo Ichisugi Daiki Azegami Naoki Toyama Hidetaka Yuge
Two molecular structures of a complex C26H16Cl2N2Pd (1) with a benzene hemisolvate (1•0.5C6H6) and a complex C34H20Cl2N2Pd (2) revealed similar conformations: one side of the arylethynyl group is flat to the bipyridine plane while the other side of the arylethynyl group is highly twisted to the plane because rhomb-like dimer fragments are formed between respective two complexes through CH⋯π interactions. The Hirshfeld surface analysis indicates that the most important contributions for the crystal packing of 1 are from H⋯H (33.6%), C⋯H/H⋯C (28.3%), Cl⋯H/H⋯Cl (17.8%), and C⋯C (10.6%) interactions and those of 2 are from H⋯H (36.5%), C⋯H/H⋯C (26.0%), Cl⋯H/H⋯Cl (15.7%), and C⋯C (12.3%) interactions, indicating the remarkable CH⋯π and electron distribution of molecules by Cl ions. The benzene solvate molecule of 1•0.5C6H6 performs to fill the internal space instead of the naphthyl group. Detailed crystallographic and DFT studies were performed to understand the molecular structures and the corresponding supramolecular associations.
]]>Crystals doi: 10.3390/cryst14030254
Authors: Sara Calistri Alessandro Gessi Giuseppe Marghella Stefania Bruni Alberto Ubaldini
Ag2MoO4 crystals were prepared by a precipitation method by mixing parent solutions of silver nitrate and sodium molybdate. The effects of experimental parameters such as temperature, concentration, and pH were studied. The samples were found to be crystalline, pure, and monophasic in all cases, except in the case of very low pH. The precipitation leads to the formation of the cubic phase β and no secondary phase is present within the limits of detection of XRD and Raman spectroscopy. However, in some cases, at high temperature and high pH, silver oxide nanoparticles form on the surfaces of the crystals, which create a fluorescence background in the Raman spectra, which is otherwise absent. Analyses with the electron microscope have highlighted that the most common crystalline shape is octahedral, which is the most prevalent at low temperatures and pH around 7, but others are also possible, in particular at high temperatures. No growth occurs after precipitation, so crystals with different appearances form at the same time.
]]>Crystals doi: 10.3390/cryst14030253
Authors: Bohan Guo Guohao Yu Li Zhang Jiaan Zhou Zheming Wang Runxian Xing An Yang Yu Li Bosen Liu Xiaohong Zeng Zhongkai Du Xuguang Deng Zhongming Zeng Baoshun Zhang
This article presents the utilization of the chemical–mechanical polishing (CMP) method to fabricate high-performance N-polar GaN/AlGaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) through layer transfer technology. The nucleation and buffer layers were removed via CMP to attain a pristine N-polar GaN surface with elevated smoothness, featuring a low root-mean-square (RMS) roughness of 0.216 nm. Oxygen, carbon, and chlorine impurity elements content were low after the CMP process, as detected via X-ray photoelectron spectroscopy (XPS). The electrical properties of N-polar HEMTs fabricated via CMP exhibited a sheet resistance (Rsh) of 244.7 Ω/sq, a mobility of 1230 cm2/V·s, and an ns of 2.24 × 1013 cm−2. Compared with a counter device fabricated via inductively coupled plasma (ICP) dry etching, the CMP devices showed an improved output current of 756.1 mA/mm, reduced on-resistance of 6.51 Ω·mm, and a significantly reduced subthreshold slope mainly attributed to the improved surface conditions. Meanwhile, owing to the MIS configuration, the reverse gate leakage current could be reduced to as low as 15 μA/mm. These results highlight the feasibility of the CMP-involved epitaxial layer transfer (ELT) technique to deliver superior N-polar GaN MIS-HEMTs for power electronic applications.
]]>Crystals doi: 10.3390/cryst14030252
Authors: Mohamed Khitouni Joan-Josep Suñol
This Special Issue entitled “Magnetic, Dielectric, Electrical, Optical and Thermal Properties of Crystalline Materials” is devoted to a general overview of the subject of crystalline materials and may extend to the nanocrystalline field [...]
]]>Crystals doi: 10.3390/cryst14030251
Authors: Bernardo A. Nogueira Chiara Castiglioni
One of the biggest challenges in the field of material science lies in understanding the structure and behavior of crystalline materials and nanostructures [...]
]]>Crystals doi: 10.3390/cryst14030250
Authors: Gheorghe Bădărău Mihai Popa George Stoian Ana-Maria Roman Radu-Ioachim Comăneci Bogdan Pricop Nicanor Cimpoeșu Leandru-Gheorghe Bujoreanu
The paper analyzes the occurrence of evenly spaced cracks on the surface of lamellar specimens of Fe-28Mn-6Si-5Cr (mass %) shape-memory alloy (SMA), during cold rolling. The specimens were hot rolled and normalized and developed cold rolling cracks with an approximate spacing of about 1.3 mm and a depth that increased with the thickness-reduction degree. At normalized specimens, X-ray diffraction patterns revealed the presence of multiple crystallographic variants of brittle α′ body-bcc martensite, which could be the cause of cold-rolling cracking. Both normalized and cold-rolled specimens were analyzed using scanning electron microscopy SEM. SEM micrographs revealed the presence of several crystallographic variants of α′-body-centered cubic (bcc) and ε hexagonal close-packed (hcp) martensite plates within a γ-face-centered cubic (fcc) austenite matrix in a normalized state. High-resolution SEM, recorded after 25% thickness reduction by cold-rolling, emphasized the ductile character of the cracks by means of an array of multiple dimples. After additional 33% cold-rolling thickness reduction, the surface of crack walls became acicular, thus revealing the fragile character of failure. It has been argued that the specimens cracked in the neutral point but preserved their integrity owing to the ductile character of γ-fcc austenite matrix.
]]>Crystals doi: 10.3390/cryst14030249
Authors: Ana Mouquinho Maria Teresa Barros João Sotomayor
This study delved into the correlation between the chain length of PEG polymerizable oligomers and the electro-optical properties exhibited by the resultant PDLC films. A range of di(meth)acrylate oligomers derived from polyethylene glycol with varying molecular weights (Mn = 1000, 2000, 4000, and 6000 g mol−1) was synthesized for incorporation as the polymer matrix in PDLC devices. Comprehensive analyses employing 1H-NMR, 13C-NMR, and MALDI-TOF mass spectroscopy were conducted to validate the structure and purity of the synthesized products. The investigation revealed a significant influence of pre-polymer molecular chain length on the thermal properties of the polymer, including amorphousness and crystallinity, which in turn impact the permanent memory effect. Specifically, it was observed that amorphous PEG polymers serve as an ideal matrix for fostering the permanent memory effect in PDLCs. Among the polymerizable PEG oligomers examined, those with a molecular weight of 1000 g/mol yielded polymer chains existing in an amorphous state, exhibiting a glass transition temperature lower than room temperature (−50 °C). This characteristic imparts flexibility and mobility to the polymer matrix chains, facilitating a 37% permanent memory effect. Conversely, longer polymer chains lead to the formation of crystal aggregates, resulting in semi-crystalline polymer matrices. This reduces the malleability of the polymer chains, thereby nullifying the permanent memory effect in the corresponding PDLC devices.
]]>Crystals doi: 10.3390/cryst14030248
Authors: Renny Maria Losus Simran Chaudhary Liliana Dobrzańska
A series of new Ag(I) complexes with 2,6-bis[(imidazol-2-yl)thiomethyl]naphthalene (L) and a range of counterions (X−) such as PF6− (1, 2), SbF6− (3), and CF3SO3− (4) was prepared. As shown by SCXRD studies, all of these are 1D coordination polymers with a waved chain motive and general formula {[AgL]X}n. Two methanol solvates containing PF6− (1) and SbF6− (3) counterions are isostructural. The triflate counterion leads to the formation of a topologically equivalent structural motive, with a different conformation of the ligand in the 1D chain and a different crystal packing as a result of the presence of another set of intermolecular interactions. The presence of water in 2 leads to a significant change in the conformation of the ligand. The naphthalene rings show a different orientation towards the imidazole rings, which is energetically less favorable but is stabilized by an extended net of intermolecular interactions with the counterion, which leads to an efficient crystal packing.
]]>Crystals doi: 10.3390/cryst14030247
Authors: Yin-Pai Lin Elina Neilande Hanna Bandarenka Siarhei Zavatski Inta Isakoviča Sergei Piskunov Dmitry Bocharov Eugene A. Kotomin
Excited state calculations are performed to predict the electronic structure and optical absorption characteristics of Cu-doped anatase TiO2 nanofilms, focusing on their (101) and (001) surface terminations. Using model structures that successfully represent the equilibrium positions of deposited Cu atoms on the TiO2 surface, a comprehensive analysis of the absorption spectra for each considered model is made. The proposed modeling reveals phenomena when photogenerated electrons from TiO2 tend to accumulate in the vicinity of the deposited Cu atoms exposed to photon energies surpassing the band gap of TiO2 (approximately 3.2 eV). The crucial transition states that are essential for the creation of potential photocatalytic materials are identified through detailed calculations of the excited states. These insights hold substantial promise for the strategic design of advanced photocatalytic materials. The obtained results provide a base for subsequent analyses, facilitating the determination of heightened surface reactivity, photostimulated water splitting, and antibacterial properties.
]]>Crystals doi: 10.3390/cryst14030246
Authors: Stavroula Maritsa Stavros Deligiannis Petros E. Tsakiridis Anna D. Zervaki
The Laser Beam Welding (LBW) of aluminum alloys has attracted significant interest from industrial sectors, including the shipbuilding, automotive and aeronautics industries, as it expects to contribute to significant cost reduction associated with the production of high-quality welds. To comprehend the behavior of welded structures in regard to their damage tolerance, the application of fracture mechanics serves as the instrumental tool. However, the methods employed overlook the changes in the microstructure within the Heat-Affected Zone (HAZ), which leads to the degradation of the mechanical properties of the material. The purpose of this study is to simulate microhardness evolution in the HAZ of AA2198-T351 LBW. The material represents the latest generation of Al-Cu-Li alloys, which exhibit improved mechanical properties, enhanced damage tolerance behavior, lower density and better corrosion and fatigue crack growth resistance than conventional Al-Cu alloys. In this work, the microhardness profile of LBW AA2198 was measured, and subsequently, through isothermal heat treatments on samples, the microhardness values of the HAZ were replicated. The conditions of the heat treatments (T, t) were selected in line with the thermal cycles that each area of the HAZ experienced during welding. ThermoCalc and DICTRA were employed in order to identify the strengthening precipitates and their evolution (dissolution and coarsening) during the weld thermal cycle. The microstructure of the heat-treated samples was studied employing LOM and TEM, and the strengthening precipitates and their characteristics (volume fraction and size) were defined and correlated to the calculations and the experimental conditions employed during welding. The main conclusion of this study is that it is feasible to imitate the microstructure evolution within the HAZ through the implementation of isothermal heat treatments. This implies that it is possible to fabricate samples for fatigue crack growth tests, enabling the experimental examination of the damage tolerance behavior in welded structures.
]]>Crystals doi: 10.3390/cryst14030245
Authors: Aarón Calvo-Villoslada Paloma Fernández Belén Sotillo
Joule heating of niobium (Nb) metal wires by running a high electric current density through them has been used to grow Nb2O5 nanowires. The formation of a micrometric oxide layer on the Nb wires has also been observed. The size and density of the nanowires are related to the current values applied, as well as the thickness of the oxide layer formed. Characterization of both nanowires and oxide layer has been performed using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, and micro-Raman spectroscopy. It has been observed that this method allows the growth of Nb2O5 nanowires in times as short as tens of seconds.
]]>Crystals doi: 10.3390/cryst14030244
Authors: Yindong Fang Chu Yu Nikolai Kropotin Martin Seyring Katharina Freiberg Matthias Kolbe Stephanie Lippmann Peter K. Galenko
The solidification of Inconel 718 alloy (IN718) from undercooled liquid is studied. The solidification kinetics is evaluated in melted and undercooled droplets processed using the electromagnetic levitation (EML) technique by the temperature–time profiles and solid/liquid (S/L) interface movement during recalescence. The kinetics is monitored in real time by special pyrometrical measurements and high-speed digital camera. It is shown that the growth velocity of γ-phase (the primary phase in IN718), the final crystalline microstructure (dendritic and grained), and the mechanical properties (microhardness) are strongly dependent on the initial undercooling ΔT at which the samples started to solidify with the originating γ-phase. Particularly, with the increase in undercooling, the secondary dendrite arm spacing decreases from 28 μm to 5 μm. At small and intermediate ranges of undercooling, the solidified droplets have a dendritic crystalline microstructure. At higher undercooling values reached in the experiment, ΔT>160 K (namely, for samples solidified with ΔT=170 K and ΔT=263 K), fine crystalline grains are observed instead of the dendritic structure of solidified drops. Such change in the crystalline morphology is qualitatively consistent with the behavior of crystal growth kinetics which exhibits the change from the power law to linear law at ΔT≈160 K in the velocity–undercooling relationship (measured by the advancement of the recalescence front in solidifying droplets). Study of the local mechanical properties shows that the microhardness increases with the increase in the γ″-phase within interdendritic spacing. The obtained data are the basis for testing the theoretical and computational of multicomponent alloy samples.
]]>Crystals doi: 10.3390/cryst14030243
Authors: I. Yucel Akkutlu Emre Arslan Faisal Irshad Khan
Methane hydrate formation is analytically studied in the presence of the water memory effect using the classical nucleation theory. The memory effect is introduced as a change in nucleation site from a three-dimensional heterogenous nucleation on a solid surface with cap-shaped hydrate clusters (3D-HEN) to a two-dimensional nucleation on the solid hydrate residue surface with monolayer disk-shaped hydrate clusters (2D-NOH). The analysis on the stationary nucleation of methane hydrate under isobaric conditions shows that the memory effect caused an average decrease of 4.4 K in metastable zone width, or subcooling. This decrease can be erased at higher dissociation temperatures (ΔT > 17.2 K) due to a decrease in the concentration of 2D-NOH nucleation sites. Moreover, the probability of hydrate formation is estimated for the purpose of quantifying risk associated with methane hydrate formation in the presence of the memory effect.
]]>Crystals doi: 10.3390/cryst14030242
Authors: Peifeng Xiong Man Xiao Zhonghua Yao Hanxing Liu Hua Hao
Lead-free ceramics with excellent energy storage performance are important for high-power energy storage devices. In this study, 0.9BaTiO3-0.1Bi(Mg2/3Nb1/3)O3 (BT-BMN) ceramics with x wt% ZnO-Bi2O3-SiO2 (ZBS) (x = 2, 4, 6, 8, 10) glass additives were fabricated using the solid-state reaction method. X-ray diffraction (XRD) analysis revealed that the ZBS glass-added ceramics exhibited a perovskite structure, with the maximum relative density achieved at x = 6. The average grain size reduced obviously as the glass additive wt% increased. Also, the dielectric constant decreased and the breakdown strength increased with increases in the glass additives. The optimal energy storage density of 1.39 J/cm3 with an energy storage efficiency of 78.3% was obtained at x = 6 due to high maximum polarization and enhanced breakdown strength. The results demonstrate that this material is a potential candidate for high-pulse-power energy storage devices.
]]>Crystals doi: 10.3390/cryst14030241
Authors: Bohae Lee Han-Youl Ryu
We investigated the effect of cross-sectional shape and size on the light-extraction efficiency (LEE) of GaN-based blue nanorod light-emitting diode (LED) structures using numerical simulations based on finite-difference time-domain methods. For accurate determination, the LEE and far-field pattern (FFP) were evaluated by averaging them over emission spectra, polarization, and source positions inside the nanorod. The LEE decreased as rod size increased, owing to the nanorods’ increased ratio of cross-sectional area to sidewall area. We compared circular, square, triangular, and hexagonal cross-sectional shapes in this study. To date, nanorod LEDs with circular cross sections have been mainly demonstrated experimentally. However, circular shapes were found to show the lowest LEE, which is attributed to the coupling with whispering-gallery modes. For the total emission of the nanorod, the triangular cross section exhibited the highest LEE. When the angular dependence of the LEE was calculated using the FFP simulation results, the triangular and hexagonal shapes showed relatively high LEEs for direction emission. The simulation results presented in this study are expected to be useful in designing high-efficiency nanorod LED structures with optimum nanorod shape and dimensions.
]]>Crystals doi: 10.3390/cryst14030240
Authors: Shahab Ranjbar Bahadori Ryan Hart Aditi Mulgaonkar Yunfeng Wang Samuel Fuentes Yi Hong Ye Cao Jiechao Jiang Xiankai Sun Yaowu Hao
We report a simple synthesis process for a wide variety of ultrasmall nanocrystals. Simply immersing a dialysis bag containing an aqueous solution of a metal salt mixed with citric acid in a NaOH solution reservoir for 10 min, nanocrystals measuring only a few nanometers in size are formed inside the dialysis bag. We demonstrated the synthesis of ultrasmall nanocrystals of Co, Ni, Cu, Ag, Au, Pd, Cu2O, FeO, and CeO2, and found that the gradual change in pH caused by the diffusion of OH− ions through the dialysis membrane played an essential role in the formation of these nanocrystals. This method can be readily adapted for almost all transition metal elements, providing researchers in the fields of catalysis and nanomedicine an easy access to a wide range of ultrasmall metal and oxide nanocrystals.
]]>Crystals doi: 10.3390/cryst14030239
Authors: Shuo Li Hai Yang
Based on two-dimensional green phosphorene, we designed two molecular electronic devices with zigzag (Type 1) and whisker-like (Type 2) configurations. By combining density functional theory (DFT) and non-equilibrium Green’s function (NEGF), we investigated the electronic properties of Types 1 and 2. Type 1 exhibits an interesting negative differential resistance (NDR), while the current characteristics of Type 2 show linear growth in the current–voltage curve. We studied the electronic transport properties of Type 1 under uniaxial strain modulation and find that strained devices also exhibit a NDR effect, and the peak-to-valley ratio of device could be controlled by varying the strain intensity. These results show that the transport properties of green phosphorene with different edge configuration are different, and the zigzag edge have adjustable negative differential resistance properties.
]]>Crystals doi: 10.3390/cryst14030238
Authors: Carmen González-Enguita Rosario García-Giménez
The variety of types that appear in kidney stones makes it necessary to describe them to try to understand their formation. The crystalline phases recognized in stones are classified according to their chemical composition. For this reason, a study using X-ray microdiffraction, Raman spectroscopy, SEM/EDX analysis, and cathodoluminescence (CL) is recommended, to identify their composition. In the present study, this was carried out on kidney stones collected from surgeries in hospitals from Spain. The samples were collected in two representative urban centers: one from a large city, Madrid; the other with a mostly rural population, in order to contrast the possible compositions of the kidney stones. In large cities, struvite appears more frequently, although calcium oxalates are very common in both areas. An attempt was made to provide a guide to the most frequent phases, accompanied by four analysis methods that make their identification possible.
]]>Crystals doi: 10.3390/cryst14030236
Authors: Mohammed Es-Souni
Waste heat is inherent to industrial activities, IT services (e.g., data centers and microprocessors), human mobility, and many other common processes. The power lost each year in this way has been estimated in the 1000 TWh in the EU which, owing to skyrocketing energy prices and not least the urgent need for decarbonizing the economy, has engendered tremendous research efforts among scientists and engineers to recover/recycle this waste energy. Beyond established thermal engineering solutions for waste heat, advances in multifunctional materials open new paradigms for waste heat harvesting. Two smart material types are of particular focus and interest at present; these are thermoelectric and pyroelectric materials, which can both transform heat to electrical power, though via different effects. The present paper summarizes our research work on a new class of pyroelectric materials, namely <111> oriented (1 − x)(Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN-PT) and x-Pb(In1/2 Nb1/2)O3-y-Pb(Mg1/3 Nb2/3)O3-(1 − x − y)-PbTiO3 (PIN-PMN-PT) single crystals that exhibit some of the highest pyroelectric properties ever measured. First, a figure of merit for pyroelectric energy harvesting is derived, followed by a detailed assessment of the properties of the said crystals and how they depend on structure, poling, thickness, and temperature. The properties are further contrasted with those of conventional pyroelectric crystals. It is concluded that the PMN-PT-base single crystals are best suited for harvesting devices with a working temperature range from 40 to 100 °C, which encompasses waste heat generated by data centers and some chemical and industrial processes, affording the highest figure of merit among pyroelectric materials.
]]>Crystals doi: 10.3390/cryst14030237
Authors: Wenyi Hu Qichi Le Qiyu Liao Tong Wang
The effects of ultrasonic treatment on grain refinement and hydrogen removal in three kinds of magnesium alloys—Mg-3Ca, Mg-6Zn-1Ca, and AZ80 alloys—were investigated in this study. After ultrasonic treatment, the grains of the magnesium alloys were refined to varying degrees. The degassing effect was characterized by measuring the densities and hydrogen content of ingots. The results indicated that the application of ultrasonic treatment in these magnesium alloys was able to remove hydrogen and obviously refine the microstructure. In this experiment, both the measurement of the density of the ingots and the solid-state hydrogen measurement reflected the degree of degassing. The highest degassing efficiencies were 53.8%, 67.5%, and 34.9% for the Mg-3Ca, Mg-6Zn-1Ca, and AZ80 alloys, respectively. The lowest hydrogen content of the AZ80 alloy reached 8.2 cm3/100 g, and the corresponding tensile strengths were 174 Mpa, 79 Mpa, and 6.2%, which represented increases of 41.5%, 38.6%, and 87.9%, respectively. The cavitation effect and acoustic streaming effect with an appropriate ultrasonic treatment duration resulted in grain refinement, degassing, and the uniform dispersion of second phases. This can significantly improve mechanical properties and provide a basis for industrial production.
]]>Crystals doi: 10.3390/cryst14030234
Authors: Cengceng Dong Chunlei Ruan
The population balance equations (PBEs) serve as the primary governing equations for simulating the crystallization process. Two-dimensional (2D) PBEs pertain to crystals that exhibit anisotropic growth, which is characterized by changes in two internal coordinates. Because PBEs are the hyperbolic equations, it becomes imperative to establish a high-resolution scheme to reduce numerical diffusion and numerical dispersion, thereby ensuring accurate crystal size distribution. This paper uses Euler’s first-order explicit (EE) method–Peridynamic Differential Operator (PDDO) to solve 2D PBE, namely, the EE method for discretizing the time derivative and the PDDO for discretizing the internal crystal-size derivative. Five examples, including size-independent growth with smooth and non-smooth distributions, size-dependent growth, nucleation, and size-independent/dependent growth for batch crystallization are considered. The results show that the EE–PDDO method is more accurate than the HR method and that it is as good as the fifth-order Weighted Essential Non-Oscillatory (WENO) method in solving 2D PBE. This study extends the EE–PDDO method to the simulation of 2D PBE, and the advantages of the EE-PDDO method in dealing with discontinuous and sharp front problems are demonstrated.
]]>Crystals doi: 10.3390/cryst14030235
Authors: Dengxiaojiang Zhao Zhenpei Chen Borui Li Shi Feng Nengneng Luo
AgNbO3 (AN) lead-free antiferroelectric material has attracted great attention in recent years. However, little focus has been directed toward a single crystal that can provide more basic information. In this study, we successfully grew high-quality AN single crystals, using a flux method, with dimensions of 5 × 5 × 3 mm3. A systematic investigation into the crystal structure, domain structure, and electrical properties of a [001]-oriented AN single crystal was conducted. X-ray diffraction and domain structure analysis revealed an orthorhombic phase structure at room temperature. Stripe-like 90° domains aligning parallel to the [110] direction with a thickness of approximately 10–20 μm were observed using a polarized light microscope. The temperature dependence of dielectric permittivity showed M1-M2, M2-M3, and M3-O phase transitions along with increasing temperature, but the phase transition temperatures were slightly higher than those of ceramic. The AN single crystal also exhibited double polarization-electric field (P-E) hysteresis loops, which enabled good recoverable energy-storage density and efficiency comparable to ceramic. Additionally, double P-E loops were kept stable at various temperatures and frequencies, demonstrating robust stability and confirming typical antiferroelectric characteristics. Our work provides valuable insights into understanding the fundamental antiferroelectric properties of AN-based materials.
]]>Crystals doi: 10.3390/cryst14030233
Authors: Nikolay Velinov Tanya Petrova Daniela Karashanova Genoveva Atanasova Daniela Kovacheva
Nanocrystalline materials with the composition of (Cu0.5Ni0.5)yFe3−yO4 and a spinel structure were synthesized by the auto-combustion sol–gel method. The materials were characterized by powder X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 physisorption. A decrease in the unit cell parameter and increase in the crystallite size with a decrease in the copper and nickel content in ferrites were evidenced. Mössbauer analysis determined that iron ions are in the 3+ states in all compositions. Transmission electron microscopy showed that synthesized ferrite materials consisted of nanoparticles with narrow size distributions. The catalytic properties of synthesized ferrites were studied in the reaction of ethyl acetate oxidation and methanol decomposition. The conversion of ethyl acetate and CO2 selectivity increased with temperature, and this effect was most pronounced for (Cu0.5Ni0.5)0.5Fe2.5O4, for which the main part of the particles possessed sizes below 10 nm, and the mean diameter was calculated to be 4.3 nm. The catalytic activity in the reaction of methanol decomposition was the highest for (Cu0.5Ni0.5)0.25Fe2.75O4, and it decreased with the increase in Cu and Ni content in the samples. The analysis of the samples after the catalytic test indicated significant reduction transformations within the catalysts. Under the reaction medium, the spinel phase decomposed through the formation of Hägg carbide.
]]>Crystals doi: 10.3390/cryst14030232
Authors: Qiangqiang Chen Jian Shang E Xue
In this paper, the tribological behavior of Cu-SiO2 composite against 1045 steel was studied. Based on the characterization of worn surface, worn subsurface and wear debris in morphology and composition, the friction layer effects on the tribological behavior of coupled materials and the wear mechanism were discussed. Abrasive wear and adhesive wear are the dominant mechanisms at the 0.56 m/s–1.12 m/s condition. Delamination wear and oxidation wear are the dominant wear mechanisms at the 1.68 m/s–2.24 m/s condition. Plastic and thermal deformation cause the evolution in morphology and structure of the tribolayer of Cu-SiO2. There is a certain correlation between the friction coefficient and the variation in friction temperature during sliding wear of Cu-SiO2 and 1045 steels. The addition of SiO2 induces the accumulation of frictional heat at the friction interface, which leads to an increase in the average temperature of the contact surface and transfer.
]]>Crystals doi: 10.3390/cryst14030231
Authors: Frederik Van Acker Bo-Han Lin Chun-Ta Wang Kristiaan Neyts Jeroen Beeckman
Nematic chiral liquid crystals (CLCs) are characterized by a helical arrangement of nematic LC molecules. A layer of CLC typically exhibits an optical reflection band due to Bragg reflection in the helical structure. When several layers of CLC are spin-coated and polymerized on top of each other without a barrier layer in between, defect modes can form in their reflection spectrum. By comparing experimental results and simulations, we investigate the origin of the defect modes, thereby revealing details on the behavior of the materials at the interfaces during deposition. Simulations show that these defect modes can originate from the migration of chiral dopant leading to a layer with a smaller pitch or from a discontinuity in the director orientation at the interface between two layers.
]]>Crystals doi: 10.3390/cryst14030229
Authors: Huanhuan Li Jinyuan Ma Guang Li Wenzhu Zhang Xianheng Bao Yu Shi
The 2205 duplex stainless steel (DSS) produced by selective laser melting (SLM) exhibits high strength (1078.8 MPa) but poor plasticity (15.2%) owing to the high cooling rate during SLM, which inhibits the formation of austenite and creates a nearly entirely ferritic microstructure. The dual-phase nature can be restored through solution annealing, which enables well-matched strength and plasticity, but which has not been extensively studied. We investigate the effects of 5 min, 30 min, and 120 min of solution annealing at 1000 °C on the dual-phase ratio, grain size, texture strength, inclusions, grain boundary characteristics, and mechanical properties of SLM-manufactured 2205 DSS. After 30 min of solution annealing, the elongation increased to 32.2% owing to the restoration of the dual-phase structure, the reduction in dislocation density, the weakening of texture, and the decrease in grain size. Increasing solution annealing time also corresponded to a decrease in the ultimate tensile strength (from 831.7 to 787.5 MPa) and yield strength (from 610.3 to 507.8 MPa) due to grain coarsening and the gradual transformation of ferrite to austenite. Furthermore, the mechanism of the transformation from ferrite to austenite was proposed, and it was observed that the transformation of MnSiO3 to MnCrO4 provided nucleation sites for austenite.
]]>Crystals doi: 10.3390/cryst14030230
Authors: Petr Král Jiří Dvořák Marie Kvapilová Andrej G. Kadomtsev Václav Sklenička
This work investigates the creep behavior of severely deformed commercial aluminum. The commercial aluminum was processed by helical rolling (HR) and equal-channel angular pressing (ECAP) at room temperature. During these processes, the equivalent strain up to about 4 was imposed into the as-received material. The creep testing at 200 °C revealed that HR and ECAP significantly increased the time to fracture compared to the as-received material. The stress dependences showed that the value of stress exponent n decreased with the value of the imposed strain. The stress-change tests showed that as-received and severely deformed states exhibited different recovery rates after unloading. The microstructure analysis showed that creep behavior was influenced by the microstructure formed during severe plastic deformation. The relationships between creep behavior and microstructure in the investigated states are discussed.
]]>Crystals doi: 10.3390/cryst14030228
Authors: Hong Zhong Jason Lonergan John S. McCloy Scott P. Beckman
Technetium-99 is a highly radioactive isotope with a long half-life that is common in nuclear waste. It volatizes at a low temperature, which poses a significant challenge to the clean-up and containment processes. Due to difficulties in purifying technetium compounds, their thermophysical properties have not been measured or calculated. Here, first principle methods are used along with the quasi quasi-harmonic harmonic approximation to compute the Debye temperature, volumetric thermal expansion coefficient, bulk modulus, and heat capacity of rutile TcO2 for temperatures ranging from 0 to 1500 K and applied pressures ranging from 0 to 255 GPa. The computed atomic structures agree well with the results from diffraction measurements. The computed thermophysical properties are in the neighborhood of other rutile metal oxides and, in particular, are within approximately 10–13% of rutile ReO2, which is frequently used as a substitute for TcO2 in experimental studies.
]]>Crystals doi: 10.3390/cryst14030227
Authors: Rositsa Nikolova Vladislav Kostov-Kytin Nadia Petrova Krasimir Kossev Rositsa Titorenkova Gergana Velyanova
Urea complexes of magnesium sulfate have been intensively studied due to their application in many areas of life, including agricultural chemistry, pharmacy, medicine, etc. The aim of this study is to add new knowledge about the trends and consistencies in the preparation procedures of MgSO4·nOC(NH2)2·mH2O phases. A set of analytical methods was used to characterize their structure, thermal and spectroscopic properties. The conditions for obtaining the three complexes in pure form were specified and the crystal structures of MgSO4·OC(NH2)2·2H2O and MgSO4·OC(NH2)2·3H2O were determined. The spectroscopic data of the considered compounds were analysed with respect to their structural and chemical properties. Thermal analyses showed that both the melting point and the urea decomposition temperature depend on the OC(NH2)2: H2O ratio in the octahedral environment of the magnesium ion in the studied structures.
]]>Crystals doi: 10.3390/cryst14030226
Authors: Zhihua Chen Longxi Chen Xiangjia Meng Yufu Ning Yang Xun
In this study, one-dimensional grating coupler on single-crystal lithium niobate thin film (lithium niobate on insulator, LNOI) that also served as a polarization splitter was designed. The coupler could separate both orthogonal polarization states into two opposite directions while coupled light from a standard single-mode fiber to a waveguide on LNOI at the same time. Using segmented and apodized designing, the peak coupling efficiencies (CEs) around telecommunication wavelength 1550 nm for fundamental TE and TM modes of −2.82 dB and −2.83 dB, respectively, were achieved. The CEs could be optimized to −1.97 dB and −1.8 dB when a metal layer was added below the silicon dioxide layer.
]]>Crystals doi: 10.3390/cryst14030225
Authors: Mengyang Yu Qiuxia Feng Zhipeng Liu Peng Zhang Xuefeng Zhu Shenglong Mu
Research has been conducted on solid oxide fuel cells (SOFCs) for their fuel flexibility, modularity, high efficiency, and power density. However, the high working temperature leads to the deterioration of materials and increased operating costs. Considering the high protonic conductivity and low activation energy, the proton conducting SOFC, i.e., the protonic ceramic fuel cell (PCFC), working at a low temperature, has been wildly investigated. The PCFC is a promising state-of-the-art electrochemical energy conversion system for ecological energy; it is characterized by near zero carbon emissions and high efficiency, and it is environment-friendly. The PCFC can be applied for the direct conversion of various renewable fuels into electricity at intermediate temperatures (400–650 °C). The construction of the PCFC directly affect its properties; therefore, manufacturing technology is the crucial factor that determines the performance. As a thinner electrolyte layer will lead to a lower polarization resistance, a uniformly constructed and crack-free layer which can perfectly bond to electrodes with a large effective area is challenging to achieve. In this work, different fabrication methods are investigated, and their effect on the overall performance of PCFCs is evaluated. This article reviews the recent preparation methods of PCFCs, including common methods, 3D printing methods, and other advanced methods, with summarized respective features, and their testing and characterization results.
]]>Crystals doi: 10.3390/cryst14030224
Authors: Rusiri Rathnasekara Grant M. Mayberry Parameswar Hari
In this work, we described the variations in the defect energy levels of four different ZnO morphologies, namely nanoribbons, nanorods, nanoparticles, and nanoshuttles. All the ZnO morphologies were grown on a seeded 4% Boron-doped p-type silicon (p-Si) wafer by using two different synthesis techniques, which are chemical bath deposition and microwave-assisted methods. The defect energy levels were analyzed by using the Deep-Level Transient Spectroscopy (DLTS) characterization method. The DLTS measurements were performed in the 123 K to 423 K temperature range. From the DLTS spectra, we found the presence of different trap-related defects in the synthesized ZnO nanostructures. We labeled all the traps related to the four different ZnO nanostructures as P1, P2, P3, P4, and P5. We discussed the presence of defects by measuring the activation energy (Ea) and capture cross-section (α). The lowest number of defect energy levels was exhibited by the ZnO nanorods at 0.27 eV, 0.18 eV, and 0.75 eV. Both the ZnO nanoribbons and nanoparticles show four traps, which have energies of 0.31 eV, 0.23 eV, 0.87 eV, and 0.44 eV and 0.27 eV, 0.22 eV, 0.88 eV, and 0.51 eV, respectively. From the DLTS spectrum of the nanoshuttles, we observe five traps with different activation energies of 0.13 eV, 0.28 eV, 0.25 eV, 0.94 eV, and 0.50 eV. The DLTS analysis revealed that the origin of the nanostructure defect energy levels can be attributed to Zinc vacancies (Vzn), Oxygen vacancies (Vo), Zinc interstitials (Zni), Oxygen interstitials (Oi), and Zinc antisites (Zno). Based on our analysis, the ZnO nanorods showed the lowest number of defect energy levels compared to the other ZnO morphologies.
]]>Crystals doi: 10.3390/cryst14030223
Authors: Gabriella Dravecz Laura Kocsor László Péter László Temleitner Dávid Gál Krisztián Lengyel
Structural changes of Er- or Yb-ion doped LiNbO3 (LN) nanocrystals were studied in relation to the high-energy ball milling process. The evolution of the size of the particles and the formation of different phases were followed by dynamic light scattering and X-ray diffraction measurements, while the electronic transitions of rare-earth (RE) ions were investigated by absorption spectroscopy in the infrared spectral range. During the milling process, RE ions left the crystal lattice and an RE2O3 phase appeared to an increasing extent next to the LN. The change in the absorption spectra and the phases formed during the grinding process were found to be very similar for both investigated RE ions and were independent of their original concentration in the starting crystal samples. The extent of the RE loss was found to be 90% after 100 min of wet grinding.
]]>Crystals doi: 10.3390/cryst14030222
Authors: Sarah Fleck Sahar Vahabzadeh
Brushite cements (BrCs) are calcium phosphate-based materials that are being widely used in hard tissue engineering applications due to their osteoconductivity, injectability, and bioresorbability. Therefore, the goal was to evaluate the effects of Mg concentration on the phase composition, setting time, and strength of BrC. Mg, which plays a vital role in bodily functions and bone health, was added to BrC at concentrations of 0.25, 0.50, 1.00, 1.50, 2.00, and 2.50 wt.%. The results showed that Mg stabilizes the TCP structure and increases the TCP content in final BrC. The initial and final setting times of BrCs increase with higher concentrations of Mg. Although 0.25 wt.% Mg did not change the setting of BrCs significantly, a higher concentration of 1.00 wt.% increased the initial setting time from 4.87 ± 0.38 min to 15.14 ± 0.88 min. Cements with Mg concentrations of 1.5 wt.% and above did not set after 4 h. Mg addition up to 0.5 wt.% did not change the compressive strength; however, higher concentrations decreased it significantly and 2.5 Mg-BrC had the lowest strength of 0.45 ± 0.09 MPs. Together, our results show that Mg can be added up to 1.00 wt.% without any adverse effect on the physical and mechanical properties of BrC.
]]>Crystals doi: 10.3390/cryst14030221
Authors: Vladimir L. Solozhenko Samir F. Matar
The superdense hexagonal boron pnictides BX (X = As, Sb, Bi), whose structures are formed by distorted tetrahedra and characterized by a quartz-derived (qtz) topology, have been predicted from first principles as potential high-pressure phases. From full geometry structure relaxation and ground state energy calculations based on quantum density functional theory (DFT), qtz BX was found to be mechanically (elastic constants) and dynamically (phonons) stable. From the energy–volume equations of state, at high but experimentally accessible pressures, qtz boron pnictides were found to be more energetically favorable than corresponding cubic zinc–blende phases with diamond-like (dia) topology. According to the electronic band structures, the zinc–blende BX have larger band gaps than the qtz phases, which can be attributed to the higher covalence of the latter. A metallic behavior is only observed for qtz BBi, which is related to the dynamic instability as it follows from the phonon band structure.
]]>Crystals doi: 10.3390/cryst14030220
Authors: Anna Guzanová Dagmar Draganovská Janette Brezinová Miroslav Tomáš Nikita Veligotskyi Štefan Kender
This paper deals with joining dissimilar materials using thermal drilling technology as well as the combination of thermal drilling and adhesive bonding. The base materials for the experimental work were deep-drawn low-carbon steel DC04, HSLA steel TL 1550-220 + Z, and structural aluminum alloy EN AW-6082 T6 (AlSi1MgMn). The geometry of the formed joints was tested metallographically as the load-bearing shear capacity under the tensile shear test of single-lapped joints and the resistance of the joints against corrosion-induced disbonding in a climate chamber. The energy dissipated by the joints up to fracture was calculated from the load–displacement curves. The hybrid joints were compared with the bonded joints with the same overlap area in terms of the load-bearing capacity and energy dissipated at joint failure. The hybrid joints formed by thermal drilling and adhesive bonding with a rubber-based adhesive confirmed the synergistic effect—the adhesive provides the high load-bearing capacity of the joint, and the bushing formed by thermal drilling increases the dissipated energy of the joint at failure. The exposure of the joints in the climatic chamber did not cause a relevant reduction in the characteristics of the joints.
]]>Crystals doi: 10.3390/cryst14030219
Authors: Wang Wei Yangguang Li Ningning Tian Tian Xie Dengpan Nie Hongyan Li Hongdong Quan Xiuguo Yang Luqian Ye Xiaohe Li Kangli Li Ye Gao
The crystal habit of pentaerythritol (PE) crystals is usually rod-shaped, which may lead to low bulk density and bad flowability compared with low aspect ratio crystals. In this study, dipentaerythritol (DPE), methylcellulose (MC), and hydroxypropyl methylcellulose (HPMC) were selected as additives to modify the morphology of PE crystals. In the presence of DPE, the bulk density of PE crystals was improved, and the aspect ratio was decreased. The modified attachment energy (AE) model was conducted to analyze changes in PE crystal habits in the presence of DPE, which characterizes the intensity of the interaction between DPE molecules and PE crystal faces. Spherical pentaerythritol crystals can be successfully prepared by adding MC and HPMC solution, and the formation mechanism can be divided into five steps.
]]>Crystals doi: 10.3390/cryst14030218
Authors: Lenka Oroszová Dávid Csík Gabriela Baranová Gábor Bortel Róbert Džunda László Temleitner Mária Hagarová Ben Breitung Karel Saksl
In the realm of advanced anode materials for lithium-ion batteries, this study explores the electrochemical performance of a high-entropy oxide (HEO) with a unique spinel structure. The equiatomic composition of CrMnFeCoCu was synthesized and subjected to a comprehensive materials characterization process, including X-ray diffraction and microscopy techniques. The multicomponent alloy exhibited a multiphase structure, comprising two face-centered cubic (FCC) phases and an oxide phase. Upon oxidation, the material transformed into a spinel oxide with a minor presence of CuO. The resulting high-entropy oxide demonstrated excellent electrochemical behavior when utilized as an anode material. Cyclic voltammetry revealed distinctive reduction peaks attributed to cation reduction and solid electrolyte interphase (SEI) layer formation, while subsequent cycles showcased high reversibility. Electrochemical impedance spectroscopy indicated a decrease in charge transfer resistance during cycling, emphasizing the remarkable electrochemical performance. Galvanostatic charge/discharge tests displayed characteristic voltage profiles, with an initial irreversible capacity attributed to SEI layer formation. The HEO exhibited promising rate capability, surpassing commercial graphite at higher current densities. The battery achieved 80% (275 mAh g−1) of its initial stable capacity at a current density of 500 mA g−1 by the 312th cycle. Post-mortem analysis revealed structural amorphization during cycling, contributing to the observed electrochemical behavior. This research highlights the potential of HEOs as advanced anode materials for lithium-ion batteries, combining unique structural features with favorable electrochemical properties.
]]>Crystals doi: 10.3390/cryst14030217
Authors: Laurent Plasseraud
The molecule glycerol (H3gly) plays a key role in sustainable and green chemistry. Having been discovered for over 200 years and produced from vegetable oils and animal fats by hydrolysis, saponification and transesterification reactions, this natural triol is today employed in a wide range of cosmetic, food, polymer and pharmaceutical applications. Moreover, it is an essential C3 precursor in the chemical industry, used in the production of several intermediates and it avoids the need for petroleum-based precursors. Less famous but just as exciting, in the domain of coordination chemistry, glycerol is also proving to be a suitable ligand, capable of binding to one or more metal centres, either directly in its triol H3gly form (rather rare), or in its various deprotonated glycerolate forms, such as [H2gly]−, [Hgly]2− and [gly]3− (in most cases). Since the 1970s, various molecular structures prepared from glycerol and metallic and organometallic precursors, ranging from mononuclear complexes to sophisticated aggregates and coordination polymers, have been isolated and characterised. On the basis of the single-crystal X-ray diffraction structures described so far in the literature and deposited in the Cambridge Structural Database, in this structural inventory, we review the different modes of coordination of glycerol and glycerolates with metals.
]]>Crystals doi: 10.3390/cryst14030216
Authors: Monika Kušter Zoran Samardžija Matej Komelj Miroslav Huskić Marko Bek Gaël Pierson Richard Kouitat-Njiwa Jean-Marie Dubois Sašo Šturm
We examined the effect of Al59Cu25Fe13B3 (at.%) quasicrystalline (QC) reinforcement particles on the mechanical and surface properties of a polymer-matrix composite by applying a technical polymer polyphthalamide (PPA). The observed increase in the tensile Young’s modulus ranged from 1810 MPa for the pure polymer to 4114 MPa for the composite with a QC filling of 35 vol.%. The elongation at fracture decreased with the filling fraction, being equal to 16.9% for a pure polymer and dropping to 4.8% for the composite with a QC filling of 35 vol.%. The same trend was noticeable with flexural Young’s modulus, which ranged from 100 MPa for a pure polymer to 125.5 MPa for the composite with 35 vol.% of QC. It was found that the increase in the mechanical strength led to a simultaneous increase of brittleness, which was reflected in a decrease of the impact strength for a pure polymer from 98.5 kJ/m2 to 42.4 kJ/m2 for composites with a QC filling of 35 vol.%. In contrast, when filled with 5 vol.% of QC, the impact strength increased by 8%. The friction coefficient against 100C6 steel dropped from 0.15 for pure PPA down to 0.10 for 5 vol.% of the QC filling, followed by an increase to 0.26 for further QC fillings up to 35 vol.%. Interestingly, a local minimum of friction was achieved at filling factors between 5 to 20 vol.% of QC. Independently, a clear surfenergy minimum was also found for the composite material with 20 vol.% of QC filling associated with a net drop in the polar component of the surfenergy. Surfenergy refers to the surface energy related to the top of the oxide layer under ambient conditions. We hypothesise that this is related to the percolation threshold at about 13 vol.% QC, reflected in the observed behaviour of both the friction coefficient and surfenergy. For the pure QC annealed in air for 1 h at 500 °C significant wear tracks were observed accompanied by a wear debris formation. On the other hand, a pure polymer exhibited slightly visible wear tracks with no apparent debris formation, and for the composites with different QC filling factors, the wear traces were barely visible with negligible debris formation.
]]>Crystals doi: 10.3390/cryst14030215
Authors: Maria-Anna Gatou Eirini Skylla Panagiota Dourou Natassa Pippa Maria Gazouli Nefeli Lagopati Evangelia A. Pavlatou
In recent times, there has been considerable interest among researchers in magnesium oxide (MgO) nanoparticles, due to their excellent biocompatibility, stability, and diverse biomedical uses, such as antimicrobial, antioxidant, anticancer, and antidiabetic properties, as well as tissue engineering, bioimaging, and drug delivery applications. Consequently, the escalating utilization of magnesium oxide nanoparticles in medical contexts necessitates the in-depth exploration of these nanoparticles. Notably, existing literature lacks a comprehensive review of magnesium oxide nanoparticles’ synthesis methods, detailed biomedical applications with mechanisms, and toxicity assessments. Thus, this review aims to bridge this gap by furnishing a comprehensive insight into various synthetic approaches for the development of MgO nanoparticles. Additionally, it elucidates their noteworthy biomedical applications as well as their potential mechanisms of action, alongside summarizing their toxicity profiles. This article also highlights challenges and future prospects for further exploring MgO nanoparticles in the biomedical field. Existing literature indicates that synthesized magnesium oxide nanoparticles demonstrate substantial biocompatibility and display significant antibacterial, antifungal, anticancer, and antioxidant properties. Consequently, this review intends to enhance readers’ comprehension regarding recent advancements in synthesizing MgO nanoparticles through diverse approaches and their promising applications in biomedicine.
]]>Crystals doi: 10.3390/cryst14030214
Authors: Akram Beniaiche Aitana Tamayo Nabil Belkhir Fausto Rubio Abdellah Chorfa Juan Rubio
Multicomponent silicate glasses are crystallized by Y2O3 addition. Depending on the Y2O3 concentration, different crystalline phases evolve. In the absence of Y2O3, a multicomponent glass crystallizes as ZnSnO3, while with the addition of just 3% of this oxide, ZnSnO3 no longer crystallizes and ZrSiO4 appears instead. Different yttrium silicate crystals are formed in all glasses containing Y2O3, but, while α-Y2Si2O7 and β-Y2Si2O7 are favored at low Y2O3 concentrations, the γ-Y2Si2O7 and y-Y2Si2O7 phases are favored at the maximum Y2O3 content. At a 12% Y2O3 concentration, barium and calcium silicate crystalline phases also evolve. Interestingly, the crystalline phases appearing on the surface of the material present different microstructures compared to crystals developed in the bulk. While the crystallized surface presents a tabular-shape type, crystallization in the bulk is of a prismatic type at low Y2O3 concentrations and of a globular (spherical) type at higher concentrations. The main crystal size ranges between 0.85 and 0.75 micrometers, but most of the crystals coalesce to form larger superstructures depending on the Y2O3 concentrations.
]]>Crystals doi: 10.3390/cryst14030213
Authors: Rachid Stefan Touzani Rostyslav Nizinkovskyi Manja Krüger
Mo-Ti-Si, Mo-Zr-B, and Mo-Hf-B are promising alloy systems for high-temperature applications as they show higher toughness and higher creep resistance than other Mo-based alloys. Regarding ductility and toughness, the chemical composition of the Mo solid-solution phase is the main parameter with which to tweak these properties of multiphase Mo-based alloys. Besides the common solid-solution hardening, one goal is to minimize embrittlement by decreasing the detrimental effects of interstitials like oxygen atoms in Mo alloys, which might be present in the bulk material due to trapping. For a better understanding of the trapping mechanisms and behavior of Mo solid solutions, the bonding situation and interaction of Mo atoms with the atoms of the alloying partners, as well as oxygen atoms, is worthwhile to investigate. For this, an in-depth analysis of the chemical bonding situation with calculations based on density functional theory in selected Mo-TM(-O) (TM = Ti, Zr, Hf) solid solutions is conducted in this work. It is shown that Ti atoms in a Mo solid solution are strong traps for oxygen atoms, while Hf and, even more clearly, Zr atoms are not. It is pointed out that the ionic and covalent interactions are the primary influence on the trapping behavior, as the change in ionic and covalent interactions between trapping and nontrapping models follows the trend Mo-1Ti > Mo-1Hf > Mo-1Zr, which resembles the trend of the trapping energy.
]]>Crystals doi: 10.3390/cryst14030212
Authors: Maria Sajdak Kamil Kornaus Dariusz Zientara Norbert Moskała Sebastian Komarek Kinga Momot Edmund Golis Łukasz Zych Agnieszka Gubernat
Titanium boride (TiB2) is a material classified as an ultra-high-temperature ceramic. The TiB2 structure is dominated by covalent bonds, which gives the materials based on TiB2 very good mechanical and thermal properties, making them difficult to sinter at the same time. Obtaining dense TiB2 polycrystals requires a chemical or physical sintering activation. Carbon and molybdenum disilicide (MoSi2) were chosen as sintering activation additives. Three series of samples were made, the first one with carbon additives: 0 to 4 wt.%; the second used 2.5, 5 and 10 wt.% MoSi2; and the third with both additions of 2 wt.% carbon and 2.5, 5 and 10 wt.% MoSi2. On the basis of the dilatometric sintering analysis, all additives were found to have a favourable effect on the sinterability of TiB2, and it was determined that sintering TiB2 with the addition of carbon can be carried at 2100 °C and with MoSi2 and both additives at 1800 °C. The polycrystals were sintered using the hot-pressing technique. On the basis of the studies conducted in this work, it was found that the addition of 1 wt.% of carbon allows single-phase TiB2 polycrystals of high density (>90%) to be obtained. The minimum MoSi2 addition, required to obtain dense sinters with a cermet-like microstructure, was 5 wt.%. High density was also achieved by the materials containing both additives. The samples with higher MoSi2 content, i.e., 5 and 10%, showed densities close to 100%. The mechanical properties, such as Young’s modulus, hardness and fracture toughness (KIc), of the polycrystals and composites were similar for samples with densities exceeding 95%. The Vickers hardness was 23 to 27 GPa, fracture toughness (KIC) was 4 to 6 MPa·m0.5 and the Young’s modulus was 480 to 540 GPa. The resulting TiB2-based materials showed potential in high-temperature applications.
]]>Crystals doi: 10.3390/cryst14030211
Authors: Henrique Videira Vitor Anes Luis Reis
This paper presents a model to calculate the opening angle of crack initiation in notched fractures subjected to multiaxial loading. To validate the proposed model, a study was performed on polished AZ31B-F magnesium alloy specimens under multiaxial high-cycle fatigue loading. The specimens exhibited a notch in the smaller cross-sectional area, which was created with a special drilling jig to promote the formation of fatigue cracks in this localized area of the specimen. The load paths used in the experiments and numerical analyses were proportional and non-proportional, resulting in different stress states in the crack front opening, which were determined by finite element analysis to validate the proposed model. To obtain more accurate numerical results for these estimates, these finite element analyses were performed using the nonlinear Chaboche plasticity model of ABAQUS® 2021 software. A sensitivity analysis was also performed to determine which load component—axial or torsional—has a greater influence on the fatigue strength and contributes significantly to the crack opening process. The results show that the type of load path and the stress level of each load component—axial and torsional—has a strong influence on the opening angle of the notch crack and the fatigue lifetime of the specimen. This result is confirmed not only by the experimentally determined fatigue strength, but also by a fractographic analysis performed on the surface of the specimens for both load paths. Moreover, the results show an acceptable correlation between the experimental results and the estimates obtained with the proposed model and the stresses obtained with the finite element analysis.
]]>Crystals doi: 10.3390/cryst14030210
Authors: Teresa Delgado Anne-Laure Pelé
In an attempt to better understand the physics governing the apparition of reverse-light-induced excited spin state trapping (LIESST) phenomena in spin crossover (SCO) compounds, we have studied the LIESST effect and the possibility of a reverse-LIESST effect in the SCO complex Zn1−xFex(6-mepy)3tren(PF6)2·CH3CN, x = 0.5%. ((6-mepy)3tren = tris{4-[(6-methyl)-2-pyridyl]-3-aza-butenyl}amine)). This complex was chosen as a good candidate to show reverse-LIESST by comparison with its unsolvated analogue, since the introduction of acetonitrile in the structure leads to the stabilisation of the high-spin state and both exhibit a very abrupt thermal spin transition. Indeed, the steep thermal spin transitions of two differently polarised crystals of Zn1−xFex(6-mepy)3tren(PF6)2·CH3CN, x = 0.5% have been characterised in detail in a first step using absorption spectroscopy and no influence of the polarisation was found. These were then fitted within the mean field model to obtain the variation in the enthalpy and entropy and the critical temperatures associated with the process, which are significantly lower with respect to the unsolvated compound due to the incorporation of acetonitrile. In a second step, the light-induced low-spin-to-high-spin transition at low temperatures based on LIESST and its subsequent high-spin-to-low-spin relaxation at different temperatures were characterised by time-resolved absorption spectroscopy, with exponential behaviour in both cases. The stabilisation of the high-spin state due to the presence of acetonitrile was evidenced. Finally, light-induced high-spin-to-low-spin state transition at low temperature based on reverse-LIESST was attempted by time-resolved absorption spectroscopy but the Fe(II) concentration was too low to observe the effect.
]]>Crystals doi: 10.3390/cryst14030209
Authors: Piotr Ruszała Maciej J. Winiarski Małgorzata Samsel-Czekała
The complex theoretical analysis of the density of states, band structures, and Fermi surfaces, based on predictions of the density functional theory methods, unveils the unique electronic properties of the LaZn1−xBi2 system. In this paper, the Zn vacancies (for x=0.5) were modeled using a modified unit cell of lower symmetry than that for a fully stoichiometric one (for x=0). The existence of several Dirac-like features in the electronic band structures was found. Some of them were found to be intimately associated with the nonsymmorphic symmetry of the system, and these were investigated in detail. The calculated Fermi surface shapes, as well as the Fermi velocity values (up to ∼1.2 ×106 m/s), are in good agreement with other analogous square-net Dirac semimetals. The combination of charge-carrier uncompensation, relatively small band splitting, and the tolerance factor for square-net semimetals t≤0.95 for LaZn0.5Bi2, constitutes a very promising indicator of the topological features of this system, warranting further experimental studies.
]]>Crystals doi: 10.3390/cryst14030208
Authors: Yan-Nan Chen Yu-Zhen Liu Qiang Sun
In this work, molecular dynamic (MD) simulations are applied to investigate the heterogeneous nucleation mechanism of KI on a graphene surface in water. As graphene is immersed in water, it mainly affects the structure of interfacial water (the topmost water layer at the interface between the substance and water). To maximize the hydrogen bonding of water, the dissolved solutes tend to accumulate to form the aggregate at the graphene surface, which undoubtedly affects the nucleation pathways of solutes in water. In comparison with homogeneous nucleation, a lower barrier may be expected during the heterogeneous nucleation of KI on a graphene surface in water. Therefore, as the graphene is immersed in water, this facilitates solute nucleation. From this work, it may be derived that heterogeneous nucleation may be closely related to the geometric characteristics of foreign surfaces, especially their geometric shape.
]]>Crystals doi: 10.3390/cryst14030207
Authors: Tianyu Wu Jun Xu Haimu Ye
Polymer physics has evolved significantly over the past century, transitioning from the early recognition of the chain structure of polymers to a mature field integrating principles from statistical mechanics, thermodynamics, and condensed matter physics. As an important part of polymer physics, polymer single crystals are crucial for understanding molecular structures and behaviors, enhancing material properties, and enabling precise functionalization. They offer insights into polymer crystallization kinetics, serve as templates for nanofabrication, and have applications in electronics, sensors, and biomedical fields. However, due to the complexity of molecular chain movement, the formation of polymer single crystals is still very difficult. Over the decades, numerous researchers have dedicated themselves to unraveling the mysteries of polymer single crystals, yielding substantial findings. This paper focus on the historical evolution and advancements in polymer single crystal research, aiming to offer valuable insights and assistance to fellow researchers in this field.
]]>Crystals doi: 10.3390/cryst14030206
Authors: Samuel Pulvermacher Florian Loebich Andreas Prahs Hangning Liu Sandra Cabeza Thilo Pirling Michael Hofmann Jens Gibmeier
For the duplex stainless steel X2CrNiMoN22-5-3, phase-specific strain pole figures (strain PFs) for the phases ferrite (bcc) and austenite (fcc) were analysed under uniaxial tensile loading for various loading states in purely elastic and elasto-plastic regimes. Experimentally, strain PFs were determined by means of in situ neutron diffraction strain measurements under defined uniaxial loading. These experimental results were compared with strain PFs calculated using elasto-plastic self-consistent (EPSC) modelling. The comparison was performed for two different {hkl} planes per phase. While classic load stress and load partitioning analyses for multi-phase materials are often limited to the load direction and a selected direction transverse to it, the results illustrate the added value of determining a strain PF, especially when a phase-specific texture is present. The comparison with experimental data shows how well the load partitioning behaviour can be predicted using common EPSC models, using the example of a duplex stainless steel. The EPSC model used was validated with the software ISODEC in its elastic range. Based on the results of the EPSC model, and taking into account the local phase-specific crystallographic texture, a prediction can be made as to what extent intergranular stresses and phase-specific textures could affect the results of a (residual) stress analysis by means of the diffraction method. This makes it possible to assess whether, for technical applications, meaningful residual stress results can be expected in certain component directions.
]]>Crystals doi: 10.3390/cryst14030205
Authors: Silvia Tofani Tiziana Ritacco Luca Maiolo Francesco Maita Romeo Beccherelli Walter Fuscaldo Dimitrios C. Zografopoulos
Microwave fabrication and design techniques are commonly employed in the terahertz (THz) domain. However, a characterization of commercially available microwave dielectric materials is usually lacking at sub-THz and THz frequencies. In this work, we characterized four substrates by Rogers and an Ordyl dry resist between 0.2 and 2 THz, in terms of relative permittivity and loss tangent. The reflectance spectra of the investigated materials were retrieved by means of THz time-domain spectroscopy in reflection mode and post-processed according to a transmission-line model in which the materials’ parameters are fit by means of the Havriliak–Negami variation of the Debye model. The relative permittivity of the investigated materials showed negligible frequency dispersion in the sub-THz and in the THz range. In terms of the loss tangent, the Rogers substrates revealed a more pronounced frequency-dispersive behavior among different materials, as dictated by the Havriliak–Negami model. The Ordyl resist was dispersive in the 0.2–1.2 THz range and presented a nearly constant loss tangent value between 1.2 and 2 THz. These results may represent a reference for the development of innovative components for THz and sub-THz emerging applications.
]]>Crystals doi: 10.3390/cryst14030204
Authors: Leonardo Oliveira Passos da Silva Tiago Nunes Lima Francisco Magalhães dos Santos Júnior Bruna Callegari Luís Fernando Folle Rodrigo Santiago Coelho
Superduplex stainless steels (SDSS) are known for their combination of good mechanical properties and excellent corrosion resistance, enabled by the microstructural balance between austenite and ferrite and an amount of alloying elements. Their application in welded components is, however, limited by the possibility of the precipitation of intermetallic phases and microstructural misbalance, which might hinder their properties, especially in the heat-affected zone (HAZ). This work introduces a methodology that relies simultaneously on physical and numerical simulations to study the HAZ in a UNS S32750 SDSS. Dimensions of the fusion zone and thermal cycles were calibrated for a numerical model using preliminary welding trials. Numerically simulated cycles for each heat input (HI) were physically reproduced in a Gleeble® simulator, and the heat-treated samples were characterized and compared with real specimens welded using the same parameters. Thermal curves resulting from the numerical simulations were successfully replicated by the Gleeble®, indicating adequate application of the desired HI. The hardness and microstructural results from simulated and welded specimens were also found to be quite similar. Therefore, the proposed methodology showed itself adequate not only for the study of duplex stainless steels, but also of materials with similar thermal and mechanical properties, including the extrapolation of welding parameters.
]]>Crystals doi: 10.3390/cryst14030203
Authors: Koki Kawabata Shusuke Okamoto Hironori Hondoh Daisuke Nagai
The polyol process is a straightforward method to produce metallic compounds through transformation from metal salt. An optimized procedure based on the polyol process in this research was developed for the selective synthesis of α-nickel hydroxide from metal salt. From various experimental results, the preparation of the sodium salt of ethylene glycol was crucial for the efficient production of α-nickel hydroxide. The structure of α-nickel hydroxide was studied by powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, transmission electron microscopy, and scanning electron microscope. The estimated Gibbs free energies for each step of the polyol process, employing density functional theory (DFT) calculations, confirmed the formation of nickel reaction intermediates, which mitigated the production of metallic nickel. The innovative point of this research is the finding that the intentional generation of nickel reaction intermediates leads to selective synthesis of α-nickel hydroxide.
]]>Crystals doi: 10.3390/cryst14030202
Authors: Peter Bury Marek Veveričík František Černobila Natália Tomašovičová Veronika Lacková Katarína Kónyová Ivo Šafařík Viktor Petrenko Oleksandr Tomchuk Milan Timko Peter Kopčanský
A study of the role of diamond nanoparticles on 5CB liquid crystal composites with Fe3O4 nanoparticles is presented. Composite ferronematic systems based on the nematic liquid crystal 5CB doped with Fe3O4 magnetic nanoparticles and additionally bound to diamond nanoparticles (DNPs), of a volume concentration of 3.2 mg/mL, 1.6 mg/mL and 0.32 mg/mL, were investigated using both magneto-optical effect and surface acoustic waves (SAWs) to study the role of diamond nanoparticles on the structural properties of ferronematic liquid crystals. The responses of light transmission and SAW attenuation to an external magnetic field were investigated experimentally under a linearly increasing and decreasing magnetic field, respectively. Investigations of the phase transition temperature shift of individual composites were also performed. The experimental results highlighted a decrease in the threshold field in the ferronematic LC composites compared to the pure 5CB as well as its further decrease after mixing Fe3O4 with diamond powder. Concerning the transition temperature, its increase with an increase in the volume fraction of both kinds of nanoparticles was registered. The role of diamond nanoparticles in the structural changes and the large residual light transition and/or attenuation (memory effect) were also observed. The presented results confirmed the potential of diamond nanoparticles in nematic composites to modify their properties which could lead to final applications.
]]>Crystals doi: 10.3390/cryst14030201
Authors: Katarzyna Lament Miłosz Grodzicki Radosław Wasielewski Piotr Mazur Antoni Ciszewski
Ultra-thin PTCDI-C8 films are vapor-deposited under ultra-high vacuum (UHV) conditions onto surfaces of p- or n-doped GaN(0001) samples. The X-ray photoelectron spectroscopy (XPS) results reveal a lack of strong chemical interaction between the PTCDI-C8 molecule and the substrate. Changes in the electronic structure of the substrate or the adsorbed molecules due to adsorption are not noticed at the XPS spectra. Work function changes have been measured as a function of the film thickness. The position of the HOMO level for films of thicknesses 3.2–5.5 nm has been determined. Energy diagrams of the interface between p- and n-type GaN(0001) substates and the PTCDI-C8 films are proposed. The fundamental molecular building blocks of the PTCDI-C8 films on GaN(0001), assembled by self-organization, have been identified. They are rows of PTCDI-C8 molecules stacked in “stand-up” positions in reference to the substrate, supported by the π–π bonds which are formed between the molecular cores of the molecules and monomolecular layers constituted by rows which are tilted in reference to the layer plane. The layers are epitaxially oriented. The epitaxial relation between the rows and the crystallographic directions of the substrate are determined. A model of the PTCDI-C8 film’s growth on GaN(0001) substrate is proposed. The 3D islands of PTCDI-C8 molecules formed on the substrate surface during film deposition are thermodynamically unstable. The Volmer–Weber type of growth observed here is a kinetic effect. Rewetting processes are noticeable after film aging at room temperature or annealing at up to 100 °C.
]]>Crystals doi: 10.3390/cryst14020199
Authors: Chenyu Zhang Qin Xu Weiwei Wang Miao Liang Li Yu Minjun Li Zhimin Zhu Liqing Huang Qianhui Li Feng Yu Yuzhu Wang Huan Zhou Qisheng Wang
To resolve photons hungry for weak diffraction samples by the crystallographic method, a double-multilayer monochromator (DMM) was employed on an undulator beamline (BL17UM) at the Shanghai Synchrotron Radiation Facility (SSRF) to provide a focused sub-micron beam with high brightness for macromolecular crystallography experiments. High-quality crystallographic datasets from model protein crystal samples were collected and processed by an existing crystallographic program for structure solution and refinement. The data quality was compared with datasets from a normal silicon crystal monochromator to evaluate the bandwidth of the DMM effect on these crystallographic data. This experiment demonstrates that multilayer optics on an undulator beamline may play a valuable role in satisfying the demands of structure-related research, which requires novel methods.
]]>Crystals doi: 10.3390/cryst14020200
Authors: Jinjiang He Qian Jia Zhaochong Ding Xingquan Wang Xiaomeng Cao Ziqi Cao Xinfu Gu
Al-Sc alloys containing high Sc content are employed as sputtering targets for the fabrication of high-performance piezoelectric films during magnetic sputtering. Due to the high proportion of the Al3Sc phase, their workability is quite limited, and they are often used in the as-cast state. In this study, the crystallography of Al3Sc dendrites in as-casted Al-10at.%Sc and Al-20at.%Sc samples is examined using electron backscatter diffraction (EBSD). With increasing Sc content, the fraction of Al3Sc also increases. The Al3Sc dendrites exhibit a cubic relationship with the Al matrix in both alloys. However, in Al-10%Sc alloys, the facets of the Al3Sc dendrites are parallel to {001} planes, while twinning is observed in Al-20at.%. The twinning plane is parallel to the {111} plane, and the dendrite growth direction aligns with the <110> directions. The different morphologies of the dendrite structures in these two alloys are discussed in relation to thermodynamic and kinetic considerations based on the phase diagram and nucleation rate.
]]>Crystals doi: 10.3390/cryst14020198
Authors: Wei Su Ming Chen Zhizhe Wang Butian Zhong Zhenhua Nie
This paper investigates the thermal battery as a research topic. We conducted an in-depth analysis of various thermal battery aspects, such as the cathode material CoS2 and electrolyte material morphology, crystal type, and interface state changes before and after service. The aim was to explore the core reaction and main failure mechanisms of the thermal battery. Prior to the reaction, the thermal battery cathode and electrolyte material consisted of pure-phase CoS2 and a composition of MgO-LiF/LiBr/LiCl. After service, the cathode and electrolyte of the single thermal battery exhibited significant morphological alterations caused by the presence of a molten state. The cathode transformed from CoS2 to Co3S4 and Co9S8 together with the presence of a marginal quantity of Co monomers visible throughout the discharge process, which was confirmed by means of XRD and XPS analyses. After the reaction, the electrolyte material was primarily made up of LiF, LiBr, and LiCl while the crystal components remained largely unaltered, albeit with apparent morphological variations. As was deduced from the thermodynamic analysis, the cathode material’s decomposition temperature stood at 655 °C, exceeding the working temperature of the thermal battery (500 °C) by a considerable margin, which is indicative of outstanding thermal durability within the thermal battery’s operational temperature range. Furthermore, the discharge reaction of the positive electrode was incomplete, resulting in reduced CoS2 residue in the thermal battery monomer after service. The reaction yielded a combination of Co3S4, Co9S8, and small amounts of Co monomers, indicating possible inconsistencies in the phase composition of the pole piece during the reaction process. In this study, we examine the distribution of residual stress in the thermal battery under various operating conditions. The simulation results indicate that exposure to a 70 °C environment for 2 h causes the maximum residual stress of the battery, which had an initial temperature of 25 °C, to reach 0.26 GPa. The thermal battery subjected to an initial temperature of 25 °C exhibited a maximum residual stress of 0.42 GPa subsequent to a 2-hour exposure to a temperature of −50 °C.
]]>Crystals doi: 10.3390/cryst14020197
Authors: Jun Min Seo Hongil Jo Myung Ho Choi Kang Min Ok Hong Young Chang Sun Woo Kim
Three new mixed metal fluoride hydrates, M2+AlF5(H2O)7 (M2+ = Fe2+, Co2+, or Ni2+), were synthesized and characterized. The crystals of M2+AlF5(H2O)7 were obtained using a hydrothermal method with a CF3COOH aqueous solution. The crystal structures displayed polymorphisms in C2/m (No. 12) or P-1 (No. 2) space groups, depending on temperature variations. The observed polymorphisms in M2+AlF5(H2O)7 are associated with changes in the bonding environment of [M(H2O)6]2+ and [AlF5(H2O)]2− octahedra, along with changes in hydrogen bonds and unit cell volumes. Infrared spectra and thermogravimetric analyses confirmed the presence of water molecules. The ultraviolet–visible spectra of M2+AlF5(H2O)7 revealed distinctive absorption bands dependent on the [M(H2O)6]2+ complex. This work provides a detailed account of the synthetic procedure, crystal structures, and spectroscopic characterization of M2+AlF5(H2O)7.
]]>Crystals doi: 10.3390/cryst14020196
Authors: Katarzyna Szwaczko Daniel M. Kamiński Anna E. Koziol
In this study, we explore the synthesis and solid-state characterization of four coumarin-3-carboxylic acid esters, each modified at the C-3 position with different cycloalkyl groups: cyclohexyl, menthyl, and iso-pulegyl. We conducted a detailed analysis of these compounds utilizing a variety of techniques such as a single-crystal X-ray diffraction, nuclear magnetic resonance (NMR), and Fourier-transform infrared (FTIR) spectroscopy. Additionally, we calculated the dipole moments for these molecules. Our findings include a thorough structural assessment, highlighting the role of noncovalent interactions through Full Interaction Maps and Hirshfeld surface analysis. This study reveals the critical influence of the weak C-H…O hydrogen bonds in determining the solid-state architecture of these esters, whereas π-π stacking interactions appear to be negligible among the studied derivatives.
]]>Crystals doi: 10.3390/cryst14020195
Authors: Masato Imai Tadahiko Kubota Atsushi Miyazawa Masahiro Aoki Haruna Mori Yuta Komaki Kenji Yoshino
Aluminum oxide (Al2O3) films have been investigated for use in various applications, and numerous deposition techniques have been reported. The spray synthesis method has the advantage of forming a thin layer of crystal at low temperatures using the appropriate precursors. A precursor prepared by diluting Methylaluminoxane with N-methyl pyrrolidone was sprayed onto a porous membrane while varying conditions such as the substrate temperature, feeding speed, and spray amount. The solution penetrated the film during spray application, and the ultra-thin layers deposited on the side wall of the internal pores were observed using a cross-sectional transmission electron microscope (XTEM). The lattice image obtained using the TEM and the composition analysis conducted using a scanning TEM and an energy-dispersive X-ray spectroscope suggest that this thin layer is a layer of Al2O3. The formation of Al2O3 occurred at lower temperatures than in previous reports. This is a major advantage for applications with low-melting-point materials. The most suitable spraying conditions were determined based on the state of deposition on the surface and inside the membrane. These conditions were applied to a three-layer separator for lithium-ion batteries and their effect on thermal stability was investigated. Through heating experiments and XRD analysis, it was confirmed that the shrinkage and melting of the separator are suppressed by spraying. This process can be expected to have wide applications in low-melting-point materials such as polyolefin.
]]>Crystals doi: 10.3390/cryst14020194
Authors: Richard Clawson Fang Fang Klee Irwin
This paper is part of a series that describes the Fibonacci icosagrid quasicrystal (FIG) and its relation to the E8 root lattice. The FIG was originally constructed to represent the intersection points of an icosahedrally symmetric collection of planar grids in three dimensions, with the grid spacing of each following a Fibonacci chain. It was found to be closely related to a five-fold compound of 3D sections taken from the 4D Elser–Sloane quasicrystal (ESQC), which is derived via a cut-and-project process from E8. More recently, a direct cut-and-project from E8 has been found which yields the FIG (presented in another paper of this series). The present paper focuses not on the full quasicrystal, but on the relationship between the root polytope of E8 (Gosset’s 421 polytope) and the core polyhedron generated in the FIG, a compound of 20 tetrahedra referred to simply as a 20-Group. In particular, the H3 symmetry of the FIG can be seen as a five-fold or “golden” composition of tetrahedral symmetry (referring to the characteristic appearance of the golden ratio). This is shown to mirror a connection between tetrahedral and five-fold symmetries present in the 421. Indeed, the rotations that connect tetrahedra contained within the 421 are shown to induce, in a certain natural way, the tetrahedron orientations in the 20-Group.
]]>Crystals doi: 10.3390/cryst14020193
Authors: Dmitry Makarov Marat Eseev Eugeny Gusarevich Viktor Matveev Ksenia Makarova Mark Borisov
It is well known that the basis of diffraction analysis of matter is scattering, including the scattering of ultrashort laser pulses. In the theory of scattering of ultrashort pulses, the pulse duration parameter is usually not taken into account, which leads to some error. This error may be more significant than the considered effects in the scattering of the pulse on the studied structure. In this paper, it is shown that the pulse duration parameter should be taken into account when scattering X-ray pulses on oriented diamonds with NV centers. It is shown that the scattering spectra can be used to judge the orientation of NV centers in the diamond structure. The obtained results may be very different from the widely used theory of diffraction analysis, which confirms the necessity of taking into account the pulse duration parameter in the diagnosis of complex structures.
]]>Crystals doi: 10.3390/cryst14020192
Authors: Tatyana Ivanova Antoaneta Harizanova Tatyana Koutzarova Benedicte Vertruyen
TiO2 and TiO2-NiO films were successfully derived by a sol–gel dip coating technology. The impact of the thermal treatments (300–600 °C) on the structural, optical and electrochromic properties was investigated. X-ray diffraction (XRD) analysis showed that TiO2 films were polycrystalline and evolved in the anatase phase. The composite TiO2-NiO films, treated at annealing temperatures below 500 °C, contained anatase titania, a small inclusion of cubic NiO and an amorphous fraction. The formation of NiTiO3 was exposed after the highest annealing at 600 °C. The presence of Ti-O-Ni bonds was determined in the composite films by Fourier-transform infrared (FTIR) spectroscopy. The optical properties and the optical band gap of TiO2-NiO films were investigated and discussed. The transparency of the electrochromic TiO2-NiO films was 76.8 and 78.3% in the 380–700 nm spectral range after film thermal treatments at 300 and 500 °C. NiO incorporation led to the narrowing of the optical band gap. The electrochromic (EC) properties of the composite films were improved compared to TiO2 films. They had higher diffusion coefficients. Their color efficiencies are 37.6 (550 nm) and 52.2 cm2/C (600 nm).
]]>Crystals doi: 10.3390/cryst14020191
Authors: Nawel Ghezali Álvaro Díaz Verde María José Illán Gómez
BaMnO3 (BM) and Ba0.9A0.1MnO3 (BM-A) (A = Ce, La or Mg) perovskite-type mixed oxides were synthesized by the aqueous sol–gel method; thoroughly characterized by ICP-OES, XRD, H2-TPR, BET, and O2-TPD; and tested as catalysts for CO oxidation under simulated automobile exhaust conditions. The characterization results indicate that the main effects of the partial substitution of Ba with A-metal in BM perovskite are the maintenance of the hexagonal structure of the perovskite and the increase in reducibility and oxygen mobility. All samples catalyze the CO to CO2 oxidation reaction in the different reactant mixtures employed, showing the best performance for the mixture with the lowest CO/O2 ratio and in the presence of a dopant in the BM perovskite formulation. BM-La is the most active catalyst for improving CO oxidation, as it is the most reducible, and because is able to evolve oxygen at intermediate temperatures.
]]>Crystals doi: 10.3390/cryst14020190
Authors: Zhuofan Wang Hongliang Lu Yuming Zhang Chen Liu
Ultrathin encapsulation strategies show huge potential in wearable and implantable electronics. However, insightful efforts are still needed to improve the electrical and mechanical characteristics of encapsulated devices. This work introduces Al2O3/alucone nanolaminates using hybrid atomic/molecular layer deposition for ultrathin encapsulation structures employed in crystalline silicon nanomembrane (Si NM)-based metal-oxide-semiconductor capacitors (MOSCAPs). The comprehensive electrical and mechanical analysis focused on the encapsulated and bare MOSCAPs with three gate dielectric diameters (Ø) under planar and bending conditions, including concave bending radii of 110.5 mm and 85 mm as well as convex bending radii of 77.5 mm and 38.5 mm. Combined with the Ø-related mechanical analysis of the maximum strain in the critical layers and the practical investigations of electrical parameters, the encapsulated MOSCAPs with Ø 160 μm showed the most stable electro-mechanical performance partly due to the optimized position of the neutral mechanical plane. Comparison of the electrical changes in Al2O3/alucone-encapsulated MOSCAPs with Ø 160 μm, Ø 240 μm, and Ø 320 μm showed that it is beneficial to define the gate dielectric surface area of 0.02 to 0.05 mm2 for Si NM-based wearable electronics. These findings are significant for leveraging the practical applications in ultrathin encapsulation strategies for reliable operations of crystalline Si NM-based integrated circuits.
]]>Crystals doi: 10.3390/cryst14020189
Authors: Beata Cristóvão Dariusz Osypiuk Barbara Mirosław
Three new cationic complexes, [Cu4Tb2(H2L)4(NO3)4(H2O)3](NO3)2·5.5H2O·2MeOH (1), [Cu4Ho2(H2L)4(NO3)4(H2O)3](NO3)2·7.5H2O (2), and [Cu4Er2(H2 L)4(NO3)4(H2O)3](NO3)2·7H2O·3MeOH (3), were synthesized and studied using elemental and TG/DTG/DSC analyses, single-crystal X-ray diffraction, and magnetic measurements. The structure analysis showed that 1–3 crystallize as (NO3)-bridged compounds and that the lanthanide(III) ion acts as a joint connecting two [CuH2L] coordination units. In each heterotrinuclear unit, an asymmetry in the degree of planarity of the bridging CuO2Ln fragments is observed. The CuII ions are five- and six-coordinate, with distorted square pyramidal and octahedral geometry, respectively, whereas the LnIII ions are nine-coordinate. The solvates 1–3 are stable at room temperature, and their desolvation process is consistent with the loss of water and/or methanol molecules. The temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicate the weak ferromagnetic interaction between the paramagnetic centers CuII and TbIII/HoIII 1 and 2.
]]>Crystals doi: 10.3390/cryst14020188
Authors: Walerian Arabczyk Rafał Pelka Izabella Jasińska Zofia Lendzion-Bieluń
The sintering of iron ammonia synthesis catalysts (nanocrystalline iron promoted with: Al2O3, CaO and K2O) was studied under a hydrogen atmosphere, in a temperature range of 773 to 973 K to obtain stationary states. The catalysts were characterized by measuring the nitriding reaction rate under an ammonia atmosphere at 748 K to obtain steady states and the measurement of specific surface area. Chemical processes were conducted in a tubular differential reactor enabling thermogravimetric measurements and the chemical composition analysis of a gas phase under conditions allowing experiments to be carried out in the kinetic region of chemical reactions. An extended model of the active surface of the iron ammonia synthesis catalyst was presented, taking into account the influence of the gas phase composition and process temperature. The surface of iron nanocrystallites was wetted using promoters in an exothermic process associated with the formation of the surface Fes-O- bond and the change in the surface energy of iron nanocrystallites. Promoters formed on the surface of iron nanocrystallites with different structures of chemisorbed dipoles, depending on the composition of the gas phase. The occupied sites stabilized the structure, and the free sites were active sites in the process of adsorption of chemical reagents and in sintering. Based on the bonding energy of the promoter oxides and the difference in surface energy between the covered and uncovered surfaces, the wetting abilities of promoters, which can be arranged according to the order K2O > Fe3O4 > Al2O3 > CaO, were estimated. By increasing the temperature in the endothermic sintering process, the degree of surface coverage with dipoles of promoters decreased, and thus the catalyst underwent sintering. The size distribution of nanocrystallites did not change with decreasing temperature. Only the equilibrium between the glass phase and the surface of iron nanocrystallites was then established.
]]>Crystals doi: 10.3390/cryst14020187
Authors: Zhaohui Li Anna Bowman Angie Rayniak Shangping Xu
In modern society, frequent use of synthetic materials in the household and industry presents a great challenge to environmental and water quality. As such, numerous types of research have been conducted for potential removal of emerging contaminants from water using advanced materials. Earth materials, due to their low costs and vast reserves, have also been evaluated in great details for contaminant removal. In this study, a naturally occurring carbonate mineral dolomite (Dol) was assessed for the removal of an anionic dye alizarin red S (ARS) from aqueous solution before and after heat treatment to increase its performance. The ARS-removal capacities increased from 80 to 130 mmol/kg after heat treatment based on the isotherm study. And the ARS-removal efficiency rose by a factor of four as the partitioning coefficient increased from 1.5 to 6 L/mmol after heat treatment. The X-ray diffraction (XRD) analyses showed minute conversion of dolomite into calcite after samples being heated at 800 °C for 3 h. However, there were no phase changes for ARS before and after its sorption. Fourie transform infra-red (FTIR) results also showed a minute appearance of calcite after heating. Thus, the increase in ARS sorption could be due to surface reactivation of Dol after heating or due to formation of a minute amount of amorphous MgO in the system as a result of the conversion of Dol to calcite. The results from this study will add new perspectives to the utilization of Earth materials for environmental application.
]]>Crystals doi: 10.3390/cryst14020186
Authors: Satish K. Shekhawat Rajesh K. Khatirkar Murat Demiral
The lattice rotation behavior of low-carbon (LC) steel subjected to tensile deformation was studied by electron backscatter diffraction (EBSD). The EBSD scans of the same region were taken before and after tensile deformation. The rotation of the grains was found to depend on a number of factors like the initial orientation, the size of the grains, the number of neighboring grains and the region of the grain. The region near the grain boundaries was found to have significant deviation from that of the interior of the grain. The lattice rotations were also simulated using DAMASK software. The simulations gave information about the state of stress for each grain and the strain gradients developed during the deformation. The orientation dependence of misorientation and geometrically necessary dislocations (GNDs) was also studied. It was found that the misorientations changed more gradually in α-fiber grains than in γ-fiber grains.
]]>Crystals doi: 10.3390/cryst14020185
Authors: Shao-Rong Bie Ding-Shun She Wen Yue
For purposes of optimizing the microstructure and fluorescence properties of rare-earth elements (REEs)-doped fluorapatites (FAps), various kinds of REEs (La, Pr, Sm, Eu, Gd, Ho, Er, and Yb) with the concentration of 2~20 mol.% have been inserted into the FAps framework via hydrothermal method, in order to investigate the influential mechanism of the REEs on the crystal structure, morphology, and fluorescence under the excitation of the near-ultraviolet light of the FAps. Experimental results show that the wavelength of the emitted light of the REEs-doped FAps is decided by the type of REEs. Unlike the Pr/Yb- and Ho-doped FAps and with the fluorescence of red and green emitted light, respectively, the Er-doped FAps show a blue light emission with wavelengths of 296, 401, and 505 nm, which is, moreover, different with the Eu-doped Faps, showing an orange light emission with wavelengths of 490, 594, and 697 nm. The emission luminous color is related to the lattice defects of the FAps doped with the various types and the effective doping concentration of the REEs. The luminous intensity increases with the increase in the effective doping concentration of the REEs. Nevertheless, the formation of rare-earth fluoride results in the decrease in the effective doping concentration of the REEs and the luminous intensity. The FAps with an effective doping concentration of 7 mol.% Er and 3 mol.% Eu show relative excellent fluorescence properties.
]]>Crystals doi: 10.3390/cryst14020184
Authors: Krastyo Buchkov Peter Rafailov Nikolay Minev Vladimira Videva Velichka Strijkova Todor Lukanov Dimitre Dimitrov Vera Marinova
Owing to their exceptional properties, which are usually determined by the growth conditions, 2D transition metal dichalcogenides (TMDCs) offer numerous research directions for applications in the fields of spintronics, valleytronics, and optoelectronics. Here, we focus on the chemical vapor deposition (CVD) synthesis of WSe2 (tungsten diselenide) nanoclusters/nanoflakes by using a liquid precursor for tungsten (ammonium metatungstate) on Si/SiO2, fused silica, and sapphire substrates. Various WSe2 clusters with different sizes, thicknesses, and geometries were analyzed by means of optical and atomic force microscopy (AFM) and Raman spectroscopy. The observed structures were mostly WSe2 multilayers; however, monolayer formations were also found. They showed significant morphological differences, as well as wide nucleation density and size variations, possibly related to precursor/substrate surface interactions under the same CVD synthesis conditions. The largest WSe2 domains with a lateral size of up to hundreds of micrometers were observed on sapphire, probably caused by a higher growth rate of singular nucleation sites. WSe2 domains with irregular and triangular shapes were simultaneously identified on fused silica, whereas multilayered pyramidal WSe2 structures dominated in the case of Si/SiO2 substrates. The application of polarized Raman spectroscopy to precisely determine and differentiate the characteristic vibrational modes (A1g, E2g, and 2LA(M)) enabled the unambiguous identification of 2D and/or multilayered WSe2 formations with a high crystallinity level. The presented comparative analysis of samples prepared in relatively simple synthesis conditions (moderate working temperatures and ambient pressure) provides a base for further progress of the facile metatungstate CVD method and relevant opportunities for the exploration of 2D TMDC materials.
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