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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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9 pages, 11292 KB  
Article
Epitaxial CdSe/PbSe Heterojunction Growth and MWIR Photovoltaic Detector
by Lance L. McDowell, Milad Rastkar Mirzaei and Zhisheng Shi
Materials 2023, 16(5), 1866; https://doi.org/10.3390/ma16051866 - 24 Feb 2023
Cited by 7 | Viewed by 3115
Abstract
A novel Epitaxial Cadmium Selenide (CdSe) on Lead Selenide (PbSe) type-II heterojunction photovoltaic detector has been demonstrated by Molecular Beam Epitaxy (MBE) growth of n-type CdSe on p-type PbSe single crystalline film. The use of Reflection High-Energy Electron Diffraction (RHEED) during the nucleation [...] Read more.
A novel Epitaxial Cadmium Selenide (CdSe) on Lead Selenide (PbSe) type-II heterojunction photovoltaic detector has been demonstrated by Molecular Beam Epitaxy (MBE) growth of n-type CdSe on p-type PbSe single crystalline film. The use of Reflection High-Energy Electron Diffraction (RHEED) during the nucleation and growth of CdSe indicates high-quality single-phase cubic CdSe. This is a first-time demonstration of single crystalline and single phase CdSe growth on single crystalline PbSe, to the best of our knowledge. The current–voltage characteristic indicates a p–n junction diode with a rectifying factor over 50 at room temperature. The detector structure is characterized by radiometric measurement. A 30 μm × 30 μm pixel achieved a peak responsivity of 0.06 A/W and a specific detectivity (D*) of 6.5 × 108 Jones under a zero bias photovoltaic operation. With decreasing temperature, the optical signal increased by almost an order of magnitude as it approached 230 K (with thermoelectric cooling) while maintaining a similar level of noise, achieving a responsivity of 0.441 A/W and a D* of 4.4 × 109 Jones at 230 K. Full article
(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials)
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13 pages, 2708 KB  
Article
Electronic, Optical, Mechanical, and Electronic Transport Properties of SrCu2O2: A First-Principles Study
by Sheng Jiang, Chaohao Hu, Dianhui Wang, Yan Zhong and Chengying Tang
Materials 2023, 16(5), 1829; https://doi.org/10.3390/ma16051829 - 23 Feb 2023
Cited by 3 | Viewed by 2232
Abstract
The structural, electronic, optical, mechanical, lattice dynamics, and electronic transport properties of SrCu2O2 crystals were studied using first-principles calculations. The calculated band gap of SrCu2O2 using the HSE hybrid functional is about 3.33 eV, which is well [...] Read more.
The structural, electronic, optical, mechanical, lattice dynamics, and electronic transport properties of SrCu2O2 crystals were studied using first-principles calculations. The calculated band gap of SrCu2O2 using the HSE hybrid functional is about 3.33 eV, which is well consistent with the experimental value. The calculated optical parameters show a relatively strong response to the visible light region for SrCu2O2. The calculated elastic constants and phonon dispersion indicate that SrCu2O2 has strong stability in mechanical and lattice dynamics. The deep analysis of calculated mobilities of electrons and holes with their effective masses proves the high separation and low recombination efficiency of photoinduced carriers in SrCu2O2. Full article
(This article belongs to the Section Materials Simulation and Design)
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15 pages, 4694 KB  
Article
Visual–Tactile Perception of Biobased Composites
by Manu Thundathil, Ali Reza Nazmi, Bahareh Shahri, Nick Emerson, Jörg Müssig and Tim Huber
Materials 2023, 16(5), 1844; https://doi.org/10.3390/ma16051844 - 23 Feb 2023
Cited by 6 | Viewed by 3046
Abstract
Biobased composites offer unique properties in the context of sustainable material production as well as end-of-life disposal, which places them as viable alternatives to fossil-fuel-based materials. However, the large-scale application of these materials in product design is hindered by their perceptual handicaps and [...] Read more.
Biobased composites offer unique properties in the context of sustainable material production as well as end-of-life disposal, which places them as viable alternatives to fossil-fuel-based materials. However, the large-scale application of these materials in product design is hindered by their perceptual handicaps and understanding the mechanism of biobased composite perception, and its constituents could pave the way to creating commercially successful biobased composites. This study examines the role of bimodal (visual and tactile) sensory evaluation in the formation of biobased composite perception through the Semantic Differential method. It is observed that the biobased composites could be grouped into different clusters based on the dominance and interplay of various senses in perception forming. Attributes such as Natural, Beautiful, and Valuable are seen to correlate with each other positively and are influenced by both visual and tactile characteristics of the biobased composites. Attributes such as Complex, Interesting, and Unusual are also positively correlated but dominated by visual stimuli. The perceptual relationships and components of beauty, naturality, and value and their constituent attributes are identified, along with the visual and tactile characteristics that influence these assessments. Material design leveraging these biobased composite characteristics could lead to the creation of sustainable materials that would be more attractive to designers and consumers. Full article
(This article belongs to the Special Issue Bio-Based Plastics and Biocomposite Materials)
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12 pages, 3628 KB  
Article
Fluorinated Multi-Walled Carbon Nanotubes Coated Separator Mitigates Polysulfide Shuttle in Lithium-Sulfur Batteries
by Devashish Salpekar, Changxin Dong, Eliezer F. Oliveira, Valery N. Khabashesku, Guanhui Gao, Ved Ojha, Robert Vajtai, Douglas S. Galvao, Ganguli Babu and Pulickel M. Ajayan
Materials 2023, 16(5), 1804; https://doi.org/10.3390/ma16051804 - 22 Feb 2023
Cited by 2 | Viewed by 3311
Abstract
Li-S batteries still suffer from two of the major challenges: polysulfide shuttle and low inherent conductivity of sulfur. Here, we report a facile way to develop a bifunctional separator coated with fluorinated multiwalled carbon nanotubes. Mild fluorination does not affect the inherent graphitic [...] Read more.
Li-S batteries still suffer from two of the major challenges: polysulfide shuttle and low inherent conductivity of sulfur. Here, we report a facile way to develop a bifunctional separator coated with fluorinated multiwalled carbon nanotubes. Mild fluorination does not affect the inherent graphitic structure of carbon nanotubes as shown by transmission electron microscopy. Fluorinated carbon nanotubes show an improved capacity retention by trapping/repelling lithium polysulfides at the cathode, while simultaneously acting as the “second current collector”. Moreover, reduced charge-transfer resistance and enhanced electrochemical performance at the cathode-separator interface result in a high gravimetric capacity of around 670 mAh g−1 at 4C. Unique chemical interactions between fluorine and carbon at the separator and the polysulfides, studied using DFT calculations, establish a new direction of utilizing highly electronegative fluorine moieties and absorption-based porous carbons for mitigation of polysulfide shuttle in Li-S batteries. Full article
(This article belongs to the Special Issue Recent Advances in Functional Nanomaterials)
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12 pages, 2392 KB  
Article
Optical Characterization of Thin Films by Surface Plasmon Resonance Spectroscopy Using an Acousto-Optic Tunable Filter
by Ildus Sh. Khasanov, Boris A. Knyazev, Sergey A. Lobastov, Alexander V. Anisimov, Pavel A. Nikitin and Oleg E. Kameshkov
Materials 2023, 16(5), 1820; https://doi.org/10.3390/ma16051820 - 22 Feb 2023
Cited by 6 | Viewed by 2796
Abstract
The paper presents the application of the acousto-optic tunable filter (AOTF) in surface plasmon resonance (SPR) spectroscopy to measure the optical thickness of thin dielectric coatings. The technique presented uses combined angular and spectral interrogation modes to obtain the reflection coefficient under the [...] Read more.
The paper presents the application of the acousto-optic tunable filter (AOTF) in surface plasmon resonance (SPR) spectroscopy to measure the optical thickness of thin dielectric coatings. The technique presented uses combined angular and spectral interrogation modes to obtain the reflection coefficient under the condition of SPR. Surface electromagnetic waves were excited in the Kretschmann geometry, with the AOTF serving as a monochromator and polarizer of light from a white broadband radiation source. The experiments highlighted the high sensitivity of the method and the lower amount of noise in the resonance curves compared with the laser light source. This optical technique can be implemented for nondestructive testing in the production of thin films in not only the visible, but also the infrared and terahertz ranges. Full article
(This article belongs to the Special Issue Acousto-Optical Spectral Technologies)
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13 pages, 3358 KB  
Article
Enhanced Luminescence of Yb3+ Ions Implanted to ZnO through the Selection of Optimal Implantation and Annealing Conditions
by Renata Ratajczak, Elzbieta Guziewicz, Slawomir Prucnal, Cyprian Mieszczynski, Przemysław Jozwik, Marek Barlak, Svitlana Romaniuk, Sylwia Gieraltowska, Wojciech Wozniak, René Heller, Ulrich Kentsch and Stefan Facsko
Materials 2023, 16(5), 1756; https://doi.org/10.3390/ma16051756 - 21 Feb 2023
Cited by 7 | Viewed by 2712
Abstract
Rare earth-doped zinc oxide (ZnO:RE) systems are attractive for future optoelectronic devices such as phosphors, displays, and LEDs with emission in the visible spectral range, working even in a radiation-intense environment. The technology of these systems is currently under development, opening up new [...] Read more.
Rare earth-doped zinc oxide (ZnO:RE) systems are attractive for future optoelectronic devices such as phosphors, displays, and LEDs with emission in the visible spectral range, working even in a radiation-intense environment. The technology of these systems is currently under development, opening up new fields of application due to the low-cost production. Ion implantation is a very promising technique to incorporate rare-earth dopants into ZnO. However, the ballistic nature of this process makes the use of annealing essential. The selection of implantation parameters, as well as post-implantation annealing, turns out to be non-trivial because they determine the luminous efficiency of the ZnO:RE system. This paper presents a comprehensive study of the optimal implantation and annealing conditions, ensuring the most efficient luminescence of RE3+ ions in the ZnO matrix. Deep and shallow implantations, implantations performed at high and room temperature with various fluencies, as well as a range of post-RT implantation annealing processes are tested: rapid thermal annealing (minute duration) under different temperatures, times, and atmospheres (O2, N2, and Ar), flash lamp annealing (millisecond duration) and pulse plasma annealing (microsecond duration). It is shown that the highest luminescence efficiency of RE3+ is obtained for the shallow implantation at RT with the optimal fluence of 1.0 × 1015 RE ions/cm2 followed by a 10 min annealing in oxygen at 800 °C, and the light emission from such a ZnO:RE system is so bright that can be observed with the naked eye. Full article
(This article belongs to the Section Optical and Photonic Materials)
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24 pages, 21486 KB  
Article
Characterization of Ruddlesden-Popper La2−xBaxNiO4±δ Nickelates as Potential Electrocatalysts for Solid Oxide Cells
by Kiryl Zakharchuk, Andrei Kovalevsky and Aleksey Yaremchenko
Materials 2023, 16(4), 1755; https://doi.org/10.3390/ma16041755 - 20 Feb 2023
Cited by 13 | Viewed by 3104
Abstract
Ruddlesden-Popper La2−xBaxNiO4±δ (x = 0–1.1) nickelates were prepared by a glycine-nitrate combustion route combined with high-temperature processing and evaluated for potential application as electrocatalysts for solid oxide cells and electrochemical NOx elimination. The characterization included [...] Read more.
Ruddlesden-Popper La2−xBaxNiO4±δ (x = 0–1.1) nickelates were prepared by a glycine-nitrate combustion route combined with high-temperature processing and evaluated for potential application as electrocatalysts for solid oxide cells and electrochemical NOx elimination. The characterization included structural, microstructural and dilatometric studies, determination of oxygen nonstoichiometry, measurements of electrical conductivity and oxygen permeability, and assessment of chemical compatibility with other materials. The formation range of phase-pure solid solutions was found to be limited to x = 0.5. Exceeding this limit leads to the co-existence of the main nickelate phase with low-melting Ba- and Ni-based secondary phases responsible for a strong reactivity with Pt components in experimental cells. Acceptor-type substitution of lanthanum by barium in La2−xBaxNiO4+δ is charge-compensated by decreasing oxygen excess, from δ ≈ 0.1 for x = 0 to nearly oxygen-stoichiometric state for x = 0.5 at 800 °C in air, and generation of electron-holes (formation of Ni3+). This leads to an increase in p-type electronic conductivity (up to ~80 S/cm for highly porous La1.5Ba0.5NiO4+δ ceramics at 450–900 °C) and a decline of oxygen-ionic transport. La2−xBaxNiO4+δ (x = 0–0.5) ceramics exhibit moderate thermal expansion coefficients, 13.8–14.3 ppm/K at 25–1000 °C in air. These ceramic materials react with yttria-stabilized zirconia at 700 °C with the formation of an insulating La2Zr2O7 phase but show good chemical compatibility with BaZr0.85Y0.15O3−δ solid electrolyte. Full article
(This article belongs to the Section Materials Chemistry)
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15 pages, 7293 KB  
Article
Electrochemical Impedance Spectroscopy (EIS) Explanation of Single Crystal Cu(100)/Cu(111) in Different Corrosion Stages
by Qihao Lin, Guoqing Chen, Shiwen Zou, Wenlong Zhou, Xuesong Fu and Shuyan Shi
Materials 2023, 16(4), 1740; https://doi.org/10.3390/ma16041740 - 20 Feb 2023
Cited by 11 | Viewed by 4713
Abstract
Copper and its alloys are used widely in marine environments, and anisotropic corrosion influences the corrosion kinetics of copper. Corrosion of copper in an electrolyte containing Cl− is described as a dissolution–deposition process, which is a prolonged process. Therefore, it is laborious [...] Read more.
Copper and its alloys are used widely in marine environments, and anisotropic corrosion influences the corrosion kinetics of copper. Corrosion of copper in an electrolyte containing Cl− is described as a dissolution–deposition process, which is a prolonged process. Therefore, it is laborious to clarify the corrosion anisotropy in different stages. In this paper, electrochemical impedance spectroscopy (EIS) following elapsed open circuit potential (OCP) test with 0 h (0H), 24 h (24H) and 10 days (10D) was adopted. To exclude interruptions such as grain boundary and neighbor effect, single crystal (SC) Cu(100) and Cu(111) were employed. After 10D OCP, cross-sectional slices were cut and picked up by a focused ion beam (FIB). The results showed that the deposited oxide was Cu2O and Cu(100)/Cu(111) experienced different corrosion behaviors. In general, Cu(100) showed more excellent corrosion resistance. Combined with equivalent electrical circuit (EEC) diagrams, the corrosion mechanism of Cu(100)/Cu(111) in different stages was proposed. In the initial stage, a smaller capacitive loop of Cu(111) suggested preferential adsorption of Cl− on air-formed oxide film on Cu(111). Deposited oxide and exposed bare metals also played an important role in corrosion resistance. Rectangle indentations and pyramidal structures formed on Cu(100)/Cu(111), respectively. Finally, a perfect interface on Cu(100) explained the tremendous capacitive loop and higher impedance (14,274 Ω·cm2). Moreover, defects in the oxides on Cu(111) provided channels for the penetration of electrolyte, leading to a lower impedance (9423 Ω·cm2) after 10D corrosion. Full article
(This article belongs to the Special Issue Advance in Corrosion and Protection of Metals)
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16 pages, 4668 KB  
Article
Expanded Glass for Thermal and Acoustic Insulation from Recycled Post-Consumer Glass and Textile Industry Process Waste
by Luca Cozzarini, Lorenzo De Lorenzi, Nicolò Barago, Orfeo Sbaizero and Paolo Bevilacqua
Materials 2023, 16(4), 1721; https://doi.org/10.3390/ma16041721 - 19 Feb 2023
Cited by 8 | Viewed by 2756
Abstract
The production of glass foams obtained by recycling post-consumer glass and textile industry processing waste is presented. The mechanical, thermal and acoustic properties were characterized as a function of process temperature and time. The results showed that it is possible to produce glass [...] Read more.
The production of glass foams obtained by recycling post-consumer glass and textile industry processing waste is presented. The mechanical, thermal and acoustic properties were characterized as a function of process temperature and time. The results showed that it is possible to produce glass foams with thermal and acoustic insulation properties from a mixture consisting of 96.5% of glass waste, 1% of textile waste and 2.5% of manganese dioxide, processed at temperatures between 800 and 900 °C for a time between 30 and 90 min. The samples had density in the range of 200–300 kg m−3, porosity of 87–92%, thermal conductivity of 85–105 mW m−1 K−1, noise-reducing factors of 0.15–0.40 and compressive strength of 1.2–3.0 MPa. Although their insulation performance was not as outstanding as that of polymer foams, these materials can emerge as competitive candidates for applications requiring non-flammability and high-temperature load bearing capacity in combination with low weight, mechanical strength, and thermal and acoustic insulation properties. The use of secondary raw materials (which accounted for 97.5% by weight of the synthetic blend) limits the energy required compared to that needed for the extraction, transportation and processing of primary raw materials, making these foams attractive also in terms of environmental footprint. Full article
(This article belongs to the Section Advanced and Functional Ceramics and Glasses)
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14 pages, 3665 KB  
Article
Changes in Abrasion Resistance of Cast Cr-Ni Steel as a Result of the Formation of Niobium Carbides in Alloy Matrix
by Grzegorz Tęcza
Materials 2023, 16(4), 1726; https://doi.org/10.3390/ma16041726 - 19 Feb 2023
Cited by 3 | Viewed by 2390
Abstract
Cast austenitic chromium-nickel steel is commonly used for the manufacture of machine parts and components, which are exposed to the attack of corrosive media and abrasive wear during operation. The most commonly used grades include GX2CrNi18-9 and X10CrNi18-8 as well as GX2CrNiMo17-12-2 and [...] Read more.
Cast austenitic chromium-nickel steel is commonly used for the manufacture of machine parts and components, which are exposed to the attack of corrosive media and abrasive wear during operation. The most commonly used grades include GX2CrNi18-9 and X10CrNi18-8 as well as GX2CrNiMo17-12-2 and X6CrNiMoNb17-12-2. To improve the abrasion resistance of cast chromium-nickel steel, primary niobium carbides were produced in the metallurgical process by increasing the carbon content and adding Fe-Nb. The microstructure of the obtained test castings consisted of an austenitic matrix and primary niobium carbides evenly distributed in this matrix. The measured hardness of the samples after heat treatment ranged from 215 to 240 HV and was higher by about 60 units than the hardness of the reference cast GX10CrNi18-9 steel, which had a hardness of about 180 HV. Compared to the reference cast steel, the abrasive wear resistance of the tested cast chromium-nickel steel (measured in Miller test) with contents of 4.4 and 5.4 wt% Nb increased only slightly, i.e., by 5% for the lower niobium content and 11% for the higher niobium content. Compared to ordinary cast GX10CrNi18-9 steel, the addition of 9.2 wt% Nb reduced the abrasive wear by almost 2.5 times. Full article
(This article belongs to the Special Issue Advances in Alloys - Microstructure, Manufacturing and Analysis)
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14 pages, 3491 KB  
Article
Strong and Flexible Braiding Pattern of Carbon Nanotubes for Composites: Stiff and Robust Structure Active in Composite Materials
by Fumio Ogawa, Fan Liu and Toshiyuki Hashida
Materials 2023, 16(4), 1725; https://doi.org/10.3390/ma16041725 - 19 Feb 2023
Cited by 2 | Viewed by 2462
Abstract
Carbon nanotubes (CNTs) exhibit high strength, Young’s modulus, and flexibility and serve as an ideal reinforcement for composite materials. Owing to their toughness against bending and/or twisting, they are typically used as fabric composites. The conventional multiaxial braiding method lacks tension and resultant [...] Read more.
Carbon nanotubes (CNTs) exhibit high strength, Young’s modulus, and flexibility and serve as an ideal reinforcement for composite materials. Owing to their toughness against bending and/or twisting, they are typically used as fabric composites. The conventional multiaxial braiding method lacks tension and resultant strength in the thickness direction. Some braiding patterns are proposed; however, they may have shortcomings in flexibility. Thus, this study proposed three types of braiding pattern for fabrics based on natural products such as spider net and honeycomb, in accordance with thickness-direction strength. The spider-net-based structure included wefts with spaces in the center with overlapping warps. At both sides, the warps crossed and contacted the wefts to impart solidness to the structure and enhance its strength as well as flexural stability. In addition, box-type wefts were proposed by unifying the weft and warps into boxes, which enhanced the stability and flexibility of the framework. Finally, we proposed a structure based on rectangular and hexagonal shapes mimicking the honeycomb. Moreover, finite element calculations were performed to investigate the mechanisms through which the proposed structures garnered strength and deformation ability. The average stress in fabrics becomes smaller than half (43%) when four edges are restrained and sliding is inserted. Under three-dimensional forces, our proposed structures underwent mechanisms of wrapping, warping, sliding and doubling, and partial locking to demonstrate their enhanced mechanical properties. Furthermore, we proposed a hierarchical structure specialized for CNTs, which could facilitate applications in structural components of satellites, wind turbines, and ships. The hierarchical structure utilizing discontinuity and sliding benefits the usage for practical mechanical systems. Full article
(This article belongs to the Special Issue Advanced Textile Materials: Design, Properties and Applications)
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9 pages, 2538 KB  
Article
Analog Resistive Switching and Artificial Synaptic Behavior of ITO/WOX/TaN Memristors
by Youngboo Cho, Jihyung Kim, Myounggon Kang and Sungjun Kim
Materials 2023, 16(4), 1687; https://doi.org/10.3390/ma16041687 - 17 Feb 2023
Cited by 11 | Viewed by 2472
Abstract
In this work, we fabricated an ITO/WOX/TaN memristor device by reactive sputtering to investigate resistive switching and conduct analog resistive switching to implement artificial synaptic devices. The device showed good pulse endurance (104 cycles), a high on/off ratio (>10), and [...] Read more.
In this work, we fabricated an ITO/WOX/TaN memristor device by reactive sputtering to investigate resistive switching and conduct analog resistive switching to implement artificial synaptic devices. The device showed good pulse endurance (104 cycles), a high on/off ratio (>10), and long retention (>104 s) at room temperature. The conduction mechanism could be explained by Schottky emission conduction. Further, the resistive switching characteristics were performed by additional pulse-signal-based experiments for more practical operation. Lastly, the potentiation/depression characteristics were examined for 10 cycles. The results thus indicate that the WOX-based devices are appropriate candidates for synaptic devices as well as next-generation nonvolatile memory. Full article
(This article belongs to the Special Issue Prospects of Oxide Materials Electronic Structure and Related Applications in Devices)
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11 pages, 4308 KB  
Article
Correlation-Driven Topological Transition in Janus Two-Dimensional Vanadates
by Ghulam Hussain, Amar Fakhredine, Rajibul Islam, Raghottam M. Sattigeri, Carmine Autieri and Giuseppe Cuono
Materials 2023, 16(4), 1649; https://doi.org/10.3390/ma16041649 - 16 Feb 2023
Cited by 10 | Viewed by 2675
Abstract
The appearance of intrinsic ferromagnetism in 2D materials opens the possibility of investigating the interplay between magnetism and topology. The magnetic anisotropy energy (MAE) describing the easy axis for magnetization in a particular direction is an important yardstick for nanoscale applications. Here, the [...] Read more.
The appearance of intrinsic ferromagnetism in 2D materials opens the possibility of investigating the interplay between magnetism and topology. The magnetic anisotropy energy (MAE) describing the easy axis for magnetization in a particular direction is an important yardstick for nanoscale applications. Here, the first-principles approach is used to investigate the electronic band structures, the strain dependence of MAE in pristine VSi2Z4 (Z = P, As) and its Janus phase VSiGeP2As2 and the evolution of the topology as a function of the Coulomb interaction. In the Janus phase the compound presents a breaking of the mirror symmetry, which is equivalent to having an electric field, and the system can be piezoelectric. It is revealed that all three monolayers exhibit ferromagnetic ground state ordering, which is robust even under biaxial strains. A large value of coupling J is obtained, and this, together with the magnetocrystalline anisotropy, will produce a large critical temperature. We found an out-of-plane (in-plane) magnetization for VSi2P4 (VSi2As4), and an in-plane magnetization for VSiGeP2As2. Furthermore, we observed a correlation-driven topological transition in the Janus VSiGeP2As2. Our analysis of these emerging pristine and Janus-phased magnetic semiconductors opens prospects for studying the interplay between magnetism and topology in two-dimensional materials. Full article
(This article belongs to the Special Issue Advances in Magnetoelectric Multiferroic Materials and Heterostructures: Properties, Techniques and Devises)
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18 pages, 8566 KB  
Article
Hydrothermal Synthesis of ZnO Superstructures with Controlled Morphology via Temperature and pH Optimization
by Aleksander Ejsmont and Joanna Goscianska
Materials 2023, 16(4), 1641; https://doi.org/10.3390/ma16041641 - 16 Feb 2023
Cited by 51 | Viewed by 7676
Abstract
Zinc oxide, as a widely used material in optics, electronics, and medicine, requires a complete overview of different conditions for facile and easily reproducible syntheses. Two types of optimization of ZnO hydrothermal preparation from zinc acetate and sodium hydroxide solution are presented, which [...] Read more.
Zinc oxide, as a widely used material in optics, electronics, and medicine, requires a complete overview of different conditions for facile and easily reproducible syntheses. Two types of optimization of ZnO hydrothermal preparation from zinc acetate and sodium hydroxide solution are presented, which allowed for obtaining miscellaneous morphologies of materials. The first was a temperature-controlled synthesis from 100 to 200 °C, using citric acid as a capping agent. The formation of hexagonal rods at the lowest temperature was evidenced, which agglomerated to flower-like structures at 110 and 120 °C. It was followed by transformation to flake-like roses at 160 °C, up to disordered structures composed of nanosized plates (>180 °C). The transformations were generated through a temperature change, which had an impact on the diffusion effect of hydroxide and citrate complexes. The second optimization was the hydrothermal synthesis free of organic additives and it included only a pH variation from 7.5 to 13.5. It was found that by utilizing a slow-dropping process and varying amounts of NaOH solutions, it is possible to obtain well-formed hexagonal pellets at pH 8.0–8.5. Strongly basic conditions of pH 11.0 and 13.5 impeded superstructure formations, giving small elongated particles of ZnO. All samples were characterized by high phase purity and crystallinity, with a specific surface area of 18–37 m2/g, whereas particle size distribution indicated a predominance of small particles (<1 μm). Full article
(This article belongs to the Section Materials Chemistry)
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15 pages, 5714 KB  
Article
Guard Ring Design to Prevent Edge Breakdown in Double-Diffused Planar InGaAs/InP Avalanche Photodiodes
by Yu-Chun Chen, Ruei-Hong Yan, Hsu-Chia Huang, Liang-Hsuan Nieh and Hao-Hsiung Lin
Materials 2023, 16(4), 1667; https://doi.org/10.3390/ma16041667 - 16 Feb 2023
Cited by 2 | Viewed by 3974
Abstract
We report on the design of an attached guard ring (AGR) and a floating guard ring (FGR) in a planar separate absorption, grading, charge, and multiplication In0.53Ga0.47As/InP avalanche photodiode to prevent premature edge breakdowns. The depths of the two [...] Read more.
We report on the design of an attached guard ring (AGR) and a floating guard ring (FGR) in a planar separate absorption, grading, charge, and multiplication In0.53Ga0.47As/InP avalanche photodiode to prevent premature edge breakdowns. The depths of the two Zn diffusions were utilized to manipulate the guard ring structures. Results from TCAD simulation indicate that the optimal AGR diffusion depth is right at the turning point where the breakdown current shifts from the edge of active region to the AGR region. The devices with optimal AGR depth contain significantly higher breakdown voltages than those of devices either with shallower—or without any— AGR. For the FGR design, a series of devices with different spacings between AGR and FGR and different FGR opening widths for diffusion were fabricated and characterized. We show that when the spacing is longer than the critical value, the breakdown voltage can increase ~1.5 V higher than those of the APD devices without FGR. In addition, the wider the FGR opening width, the higher the breakdown voltage. TCAD simulations were also performed to study the effect of FGR, but showed less pronounced improvements, which could be due the discrepancy between the calculated and experimental diffusion profile. Full article
(This article belongs to the Special Issue Opto/Electronics Materials and Devices Applied for Telecommunications)
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12 pages, 3917 KB  
Article
An Ultra-Broadband and Highly-Efficient Metamaterial Absorber with Stand-Up Gradient Impedance Graphene Films
by Bian Wu, Biao Chen, Shuai Ma, Ding Zhang and Hao-Ran Zu
Materials 2023, 16(4), 1617; https://doi.org/10.3390/ma16041617 - 15 Feb 2023
Cited by 6 | Viewed by 2418
Abstract
Metamaterial absorbers (MMAs) that absorb electromagnetic waves among an ultra-broad frequency band have attracted great attention in military and civilian applications. In this paper, an ultra-broadband and highly-efficient MMA is presented. The unit cell of the proposed MMA was constructed with two cross-placed [...] Read more.
Metamaterial absorbers (MMAs) that absorb electromagnetic waves among an ultra-broad frequency band have attracted great attention in military and civilian applications. In this paper, an ultra-broadband and highly-efficient MMA is presented. The unit cell of the proposed MMA was constructed with two cross-placed stand-up gradient impedance graphene films, which play a key role in improving impedance matching. Considering the trade-off between absorbing performance and processing complexity, in our design, we adopted the stand-up graphene films that have a gradient with three orders of magnitude in total. The simulated results of the proposed absorber show an ultra-broadband absorption (absorptivity > 90%) from 1.8 GHz to 66.7 GHz and a highly-efficient absorption (absorptivity > 97%) in the range of 2–21.7 GHz and 39.6–57 GHz. The field analysis was adopted to explain the mechanism of the proposed absorber. To validate this design, a prototype of 20 × 20 units was processed and assembled. The graphene films were processed with graphene conductive ink using screen print technology. The measured results are in good agreement with the simulated ones. The proposed absorber may find potential applications in the field of stealth technologies and electromagnetic interference. Full article
(This article belongs to the Special Issue Application of Graphene-Based Materials in Sensors and RF Electronics)
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14 pages, 7008 KB  
Article
Silver Nanoparticles for Fluorescent Nanocomposites by High-Pressure Magnetron Sputtering
by Tomáš Zikmund, Jiří Bulíř, Michal Novotný, Ladislav Fekete, Sergii Chertopalov, Stefan Andrei Irimiciuc, Mariana Klementová, Jarmila Balogová and Jan Lančok
Materials 2023, 16(4), 1591; https://doi.org/10.3390/ma16041591 - 14 Feb 2023
Cited by 5 | Viewed by 2357
Abstract
We report on the formation of silver nanoparticles by gas aggregation in a reaction chamber at room temperature. The size distribution of nanoparticles deposited on a silicon substrate for various lengths of an aggregation (high-pressure) chamber was investigated by atomic force microscopy. Nanoparticles [...] Read more.
We report on the formation of silver nanoparticles by gas aggregation in a reaction chamber at room temperature. The size distribution of nanoparticles deposited on a silicon substrate for various lengths of an aggregation (high-pressure) chamber was investigated by atomic force microscopy. Nanoparticles were characterized by scanning and transmission electron microscopy and spectral ellipsometry. The physical shape of the nanoparticles and its distribution was correlated with their optical properties. Metal–dielectric nanocomposites were deposited employing simultaneous deposition of Ag NPs via high-pressure magnetron sputtering and the dielectric matrix was deposited via thermal evaporation. Pure and Eu-, Er-, and Yb-doped lithium fluoride was used as the dielectric host matrix. Optical transmittance of lithium fluoride containing silver nanoparticles was measured and their theoretical absorption cross-section calculated. The nanoparticles were also embedded in Eu3+-doped downshifting and Er3+- and Yb3+-doped up-conversion materials to study their influence on emission spectra. Spectra of identical layers with and without nanoparticles were compared. Their transmittance at various annealing temperatures is also presented. Full article
(This article belongs to the Special Issue Structural, Morphological, and Optical Properties of Functional Thin Films)
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10 pages, 2714 KB  
Article
Graphene/PVDF Nanocomposite-Based Accelerometer for Detection of Low Vibrations
by Surendra Maharjan, Victor K. Samoei and Ahalapitiya H. Jayatissa
Materials 2023, 16(4), 1586; https://doi.org/10.3390/ma16041586 - 14 Feb 2023
Cited by 7 | Viewed by 2995
Abstract
A flexible piezoresistive sensor was developed as an accelerometer based on Graphene/PVDF nanocomposite to detect low-frequency and low amplitude vibration of industrial machines, which may be caused due to misalignment, looseness of fasteners, or eccentric rotation. The sensor was structured as a cantilever [...] Read more.
A flexible piezoresistive sensor was developed as an accelerometer based on Graphene/PVDF nanocomposite to detect low-frequency and low amplitude vibration of industrial machines, which may be caused due to misalignment, looseness of fasteners, or eccentric rotation. The sensor was structured as a cantilever beam with the proof mass at the free end. The vibration caused the proof mass to accelerate up and down, which was converted into an electrical signal. The output was recorded as the change in resistance (response percentage) with respect to the acceleration. It was found that this accelerometer has a capability of detecting acceleration up to 8 gpk-pk in the frequency range of 20 Hz to 80 Hz. The developed accelerometer has the potential to represent an alternative to the existing accelerometers due to its compactness, simplicity, and higher sensitivity for low frequency and low amplitude applications. Full article
(This article belongs to the Special Issue Low-Dimensional Structures for Smart Materials and Composites: Preparation, Properties and Applications)
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19 pages, 9066 KB  
Article
Epoxy and Bio-Based Epoxy Carbon Fiber Twill Composites: Comparison of the Quasi-Static Properties
by Carlo Boursier Niutta, Raffaele Ciardiello, Andrea Tridello and Davide S. Paolino
Materials 2023, 16(4), 1601; https://doi.org/10.3390/ma16041601 - 14 Feb 2023
Cited by 16 | Viewed by 2890
Abstract
In recent years, interest in sustainability has significantly increased in many industrial sectors. Sustainability can be achieved with both lightweight design and eco-friendly manufacturing processes. For example, concerns on the use of thermoset composite materials, with a lightweight design and a high specific [...] Read more.
In recent years, interest in sustainability has significantly increased in many industrial sectors. Sustainability can be achieved with both lightweight design and eco-friendly manufacturing processes. For example, concerns on the use of thermoset composite materials, with a lightweight design and a high specific strength, have arisen, since thermoset resins are not fully recyclable and are mainly petrol based. A possible solution to this issue is the replacement of the thermoset matrix with a recyclable or renewable matrix, such as bio-based resin. However, the mechanical properties of composites made with bio-based resin should be carefully experimentally assessed to guarantee a safe design and the structural integrity of the components. In this work, the quasi-static mechanical properties of composite specimens (eight layers of carbon fiber fabric) made with commercially available epoxy and a bio-based epoxy resins (31% bio content) are compared. Tensile tests on the investigated resins and tensile, compression, shear and flexural tests have been carried out on composite laminates manufactured with the two investigated resins. A finite element model has been calibrated in the LS-Dyna environment using the experimentally assessed mechanical properties. The experimental results have proven that the two composites showed similar quasi-static properties, proving that bio-based composite materials can be reliably employed as a substitute for epoxy resins without affecting the structural integrity of the component but lowering their carbon footprint. Full article
(This article belongs to the Special Issue Recent Advances in Biobased and Biodegradable Polymers)
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8 pages, 3445 KB  
Article
Effect of Surface Dispersion of Fe Nanoparticles on the Room-Temperature Flash Sintering Behavior of 3YSZ
by Angxuan Wu, Yuchen Zhu, Chen Xu, Nianping Yan, Xuetong Zhao, Xilin Wang and Zhidong Jia
Materials 2023, 16(4), 1544; https://doi.org/10.3390/ma16041544 - 13 Feb 2023
Cited by 2 | Viewed by 2052
Abstract
Arc floating in surface flashover can be controlled by reducing the interfacial charge-transfer resistance of ceramics. However, thus far, only a few studies have been conducted on methods of treating ceramic surfaces directly to reduce the interfacial charge-transfer resistance. Herein, we explore the [...] Read more.
Arc floating in surface flashover can be controlled by reducing the interfacial charge-transfer resistance of ceramics. However, thus far, only a few studies have been conducted on methods of treating ceramic surfaces directly to reduce the interfacial charge-transfer resistance. Herein, we explore the flash sintering behavior of a ceramic surface (3 mol% yttria-stabilized zirconia (3YSZ)) onto which loose metal (iron) powder was spread prior to flash sintering at room temperature (25 °C). The iron powder acts as a conductive phase that accelerates the start of flash sintering while also doping the ceramic phase during the sintering process. Notably, the iron powder substantially reduces the transition time from the arc stage to the flash stage from 13.50 to 8.22 s. The surface temperature (~1600 °C) of the ceramic substrate is sufficiently high to melt the iron powder. The molten metal then reacts with the ceramic surface, causing iron ions to substitute Zr4+ ions and promoting rapid densification. The YSZ grains in the metal-infiltrated area grow exceptionally fast. The results demonstrate that spreading metal powder onto a ceramic surface prior to flash sintering can enable the metal to enter the ceramic pores, which will be of significance in developing and enhancing ceramic–metal powder processing techniques. Full article
(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)
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12 pages, 4312 KB  
Article
Single Crystals of EuScCuSe3: Synthesis, Experimental and DFT Investigations
by Maxim V. Grigoriev, Anna V. Ruseikina, Vladimir A. Chernyshev, Aleksandr S. Oreshonkov, Alexander A. Garmonov, Maxim S. Molokeev, Ralf J. C. Locke, Andrey V. Elyshev and Thomas Schleid
Materials 2023, 16(4), 1555; https://doi.org/10.3390/ma16041555 - 13 Feb 2023
Cited by 4 | Viewed by 2206
Abstract
EuScCuSe3 was synthesized from the elements for the first time by the method of cesium-iodide flux. The crystal belongs to the orthorhombic system (Cmcm) with the unit cell parameters a = 3.9883(3) Å, b = 13.2776(9) Å, c = 10.1728(7) [...] Read more.
EuScCuSe3 was synthesized from the elements for the first time by the method of cesium-iodide flux. The crystal belongs to the orthorhombic system (Cmcm) with the unit cell parameters a = 3.9883(3) Å, b = 13.2776(9) Å, c = 10.1728(7) Å, V = 538.70(7) Å3. Density functional (DFT) methods were used to study the crystal structure stability of EuScCuSe3 in the experimentally obtained Cmcm and the previously proposed Pnma space groups. It was shown that analysis of elastic properties as Raman and infrared spectroscopy are powerless for this particular task. The instability of EuScCuSe3 in space group Pnma space group is shown on the basis of phonon dispersion curve simulation. The EuScCuSe3 can be assigned to indirect wide-band gap semiconductors. It exhibits the properties of a soft ferromagnet at temperatures below 2 K. Full article
(This article belongs to the Special Issue Advances in Density Functional Theory (DFT) Studies of Solids (Second Volume))
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18 pages, 9058 KB  
Review
The Historical Development of Infrared Photodetection Based on Intraband Transitions
by Qun Hao, Xue Zhao, Xin Tang and Menglu Chen
Materials 2023, 16(4), 1562; https://doi.org/10.3390/ma16041562 - 13 Feb 2023
Cited by 7 | Viewed by 3643
Abstract
The infrared technology is entering widespread use as it starts fulfilling a growing number of emerging applications, such as smart buildings and automotive sectors. Majority of infrared photodetectors are based on interband transition, which is the energy gap between the valence band and [...] Read more.
The infrared technology is entering widespread use as it starts fulfilling a growing number of emerging applications, such as smart buildings and automotive sectors. Majority of infrared photodetectors are based on interband transition, which is the energy gap between the valence band and the conduction band. As a result, infrared materials are mainly limited to semi-metal or ternary alloys with narrow-bandgap bulk semiconductors, whose fabrication is complex and expensive. Different from interband transition, intraband transition utilizing the energy gap inside the band allows for a wider choice of materials. In this paper, we mainly discuss the recent developments on intraband infrared photodetectors, including ‘bottom to up’ devices such as quantum well devices based on the molecular beam epitaxial approach, as well as ‘up to bottom’ devices such as colloidal quantum dot devices based on the chemical synthesis. Full article
(This article belongs to the Section Quantum Materials)
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21 pages, 3534 KB  
Article
Parametric Study of the Influence of Nonlinear Elastic Characteristics of Rail Pads on Wheel–Rail Vibrations
by Traian Mazilu, Mădălina Dumitriu and Ionuț-Radu Răcănel
Materials 2023, 16(4), 1531; https://doi.org/10.3390/ma16041531 - 12 Feb 2023
Cited by 8 | Viewed by 2436
Abstract
The rail pad is the elastic element between the rail and the sleeper that has the role of absorbing the mechanical stresses from the rail and reducing the vibrations and shocks generated by wheel–rail interactions. In this paper, the problem of the influence [...] Read more.
The rail pad is the elastic element between the rail and the sleeper that has the role of absorbing the mechanical stresses from the rail and reducing the vibrations and shocks generated by wheel–rail interactions. In this paper, the problem of the influence of the variability of the nonlinear load-deformation characteristic of rail pads (resulting from the manufacturing process) on wheel–rail vibrations is investigated. The limit load-deformation characteristics of a manufactured rail pad and the medium load-deformation characteristic resulting as the arithmetic mean of the two are considered. The nonlinear load-deformation characteristic of the ballast is also considered. All these characteristics are approximated with the help of the bilinear function and are implemented in a track model consisting of an infinite Euler-Bernoulli beam placed on a two-elastic layer continuous foundation with inertial insertion, resulting in a model with an inhomogeneous foundation. The parameters of the inhomogeneous foundation are established from the equilibrium condition under a static load. Wheel–rail vibrations are studied in terms of the contact force and the acceleration of the rail and wheel. The influence of the variability of the elastic characteristics of the rail pad manifests itself in the field of medium frequencies, which amplify or attenuate the vibration levels in certain bands of one-third of an octave. Full article
(This article belongs to the Special Issue Research and Modeling of Materials Fatigue and Fracture)
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17 pages, 12522 KB  
Article
Porous Thermoplastic Molded Regenerated Silk Crosslinked by the Addition of Citric Acid
by Alessio Bucciarelli, Nicola Vighi, Alessandra Maria Bossi, Brunella Grigolo and Devid Maniglio
Materials 2023, 16(4), 1535; https://doi.org/10.3390/ma16041535 - 12 Feb 2023
Cited by 1 | Viewed by 2649
Abstract
Thermoplastic molded regenerated silk fibroin was proposed as a structural material in tissue engineering applications, mainly for application in bone. The protocol allows us to obtain a compact non-porous material with a compression modulus in the order of a Giga Pascal in dry [...] Read more.
Thermoplastic molded regenerated silk fibroin was proposed as a structural material in tissue engineering applications, mainly for application in bone. The protocol allows us to obtain a compact non-porous material with a compression modulus in the order of a Giga Pascal in dry conditions (and in the order of tens of MPa in wet conditions). This material is produced by compressing a lyophilized silk fibroin powder or sponge into a mold temperature higher than the glass transition temperature. The main purpose of the produced resin was the osteofixation and other structural applications in which the lack of porosity was not an issue. In this work, we introduced the use of citric acid in the thermoplastic molding protocol of silk fibroin to obtain porosity inside the structural material. The citric acid powder during the compression acted as a template for the pore formation. The mean pore diameter achieved by the addition of the higher amount of citric acid was around 5 μm. In addition, citric acid could effectively crosslink the silk fibroin chain, improving its mechanical strength. This effect was proved both by evaluating the compression modulus (the highest value recorded was 77 MPa in wet conditions) and by studying the spectra obtained by Fourier transform infrared spectroscopy. This protocol may be applied in the near future to the production of structural bone scaffolds. Full article
(This article belongs to the Special Issue Synthesis, Optimization, and Reuse of Sustainable Bio-Based Materials)
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17 pages, 5382 KB  
Article
Green Synthesis, Characterization, and Empirical Thermal Conductivity Assessment of ZnO Nanofluids for High-Efficiency Heat-Transfer Applications
by Meriem Jebali, Gianpiero Colangelo and Ana Isabel Gómez-Merino
Materials 2023, 16(4), 1542; https://doi.org/10.3390/ma16041542 - 12 Feb 2023
Cited by 15 | Viewed by 3268
Abstract
ZnO nanoparticles were synthesized using lemon juice and zinc nitrate (1:1) through the green method. The structure of the biosynthesized ZnO nanoparticles was analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The morphology and the size of [...] Read more.
ZnO nanoparticles were synthesized using lemon juice and zinc nitrate (1:1) through the green method. The structure of the biosynthesized ZnO nanoparticles was analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The morphology and the size of ZnO nanoparticles were elucidated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The powder was highly dispersed and irregularly shaped and the size of the nanoparticles ranged from 28 to 270 nm, depending on the shape of the particles. Thermal conductivity of the biosynthesized ZnO PG/W mixture 40:60 (v/v) nanofluids was measured within the temperature range of 20–70 °C. Experimental results revealed a linear increase in thermal conductivity with the rise of temperature and volume fraction. The enhancement of this parameter with temperature was probably due to the different shapes of the former agglomerates. They were broken by the thermal energy in aggregates of different forms. A correlation of these structures with temperature was established. Finally, an empirical model was developed for predicting thermal conductivity with particle volume fraction and temperature. Full article
(This article belongs to the Special Issue Green Synthesis and Applications of Metallic Nanoparticles)
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13 pages, 2105 KB  
Article
Analyzing the Bolometric Performance of Vanadium Oxide Thin Films Modified by Carbon Nanotube Dispersions
by Usha Philipose, Chris Littler, Yan Jiang, Alia Naciri, Michael Harcrow and A. J. Syllaios
Materials 2023, 16(4), 1534; https://doi.org/10.3390/ma16041534 - 12 Feb 2023
Cited by 2 | Viewed by 2926
Abstract
The influence of carbon nanotube (CNT) dispersions on the electrical properties and noise signal amplitude of VOx films is investigated. For a critical range of the CNT dispersion density on VOx films, the intrinsic properties of the [...] Read more.
The influence of carbon nanotube (CNT) dispersions on the electrical properties and noise signal amplitude of VOx films is investigated. For a critical range of the CNT dispersion density on VOx films, the intrinsic properties of the VOx films are modified by the CNTs. The CNT concentrations reported in this work are about 0.3 μg/cm2 and 1.6 μg/cm2, allowing for low density and high density dispersions on the VOx film surface to be investigated. These values are higher than the percolation threshold of about 0.12 μg/cm2 for these films. The composite film exhibits a significant reduction in the temperature coefficient of resistance (TCR) (from ≈3.8% K−1 to ≈0.3% K−1) for high density dispersions. In contrast, while VOx–CNT composites with low density single wall CNT dispersions exhibit no significant change in TCR values, an approximate two orders of magnitude reduction in the low frequency 1/f noise is measured. The noise signal amplitude measured at 0.1 V and at 1.0 Hz reduces from 6 × 10−5V/(Hz) for VOx films to 5 × 10−7V/(Hz) for the low density SWCNT dispersion on VOx film and to 3 × 10−6V/(Hz) for the low density MWCNT dispersion on VOx film. The CNT concentration is the critical factor for yielding the observed changes in conductivity and low frequency noise. The results presented in this work provide a better understanding of VOx-based composites, thereby enabling the development of new, versatile and functional materials for device applications. Full article
(This article belongs to the Special Issue Feature Papers in Thin Films and Interfaces)
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15 pages, 8380 KB  
Article
Antimicrobial Properties of TiNbSn Alloys Anodized in a Sulfuric Acid Electrolyte
by Yu Mori, Satoko Fujimori, Hiroaki Kurishima, Hiroyuki Inoue, Keiko Ishii, Maya Kubota, Kazuyoshi Kawakami, Naoko Mori, Toshimi Aizawa and Naoya Masahashi
Materials 2023, 16(4), 1487; https://doi.org/10.3390/ma16041487 - 10 Feb 2023
Cited by 5 | Viewed by 2365
Abstract
TiNbSn alloy is a high-performance titanium alloy which is biosafe, strong, and has a low Young’s modulus. TiNbSn alloy has been clinically applied as a material for orthopedic prosthesis. Anodized TiNbSn alloys with acetic and sulfuric acid electrolytes have excellent biocompatibility for osseointegration. [...] Read more.
TiNbSn alloy is a high-performance titanium alloy which is biosafe, strong, and has a low Young’s modulus. TiNbSn alloy has been clinically applied as a material for orthopedic prosthesis. Anodized TiNbSn alloys with acetic and sulfuric acid electrolytes have excellent biocompatibility for osseointegration. Herein, TiNbSn alloy was anodized in a sulfuric acid electrolyte to determine the antimicrobial activity. The photocatalytic activities of the anodic oxide alloys were investigated based on their electronic band structure and crystallinity. In addition, the cytotoxicity of the anodized TiNbSn alloy was evaluated using cell lines of the osteoblast and fibroblast lineages. The antimicrobial activity of the anodic oxide alloy was assessed according to the ISO 27447 using methicillin-susceptible Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Escherichia coli. The anodic oxide comprised rutile and anatase titanium dioxide (TiO2) and exhibited a porous microstructure. A well-crystallized rutile TiO2 phase was observed in the anodized TiNbSn alloy. The methylene blue degradation tests under ultraviolet illumination exhibited photocatalytic activity. In antimicrobial tests, the anodized TiNbSn alloy exhibited robust antimicrobial activities under ultraviolet illumination for all bacterial species, regardless of drug resistance. Therefore, the anodized TiNbSn alloy can be used as a functional biomaterial with low Young’s modulus and excellent antimicrobial activity. Full article
(This article belongs to the Special Issue Mechanical Behavior of Biological and Bio-Inspired Materials)
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15 pages, 6239 KB  
Article
Mammalian Oocyte Analysis by MALDI MSI with Wet-Interface Matrix Deposition Technique
by Anna Bodzon-Kulakowska, Wiesława Młodawska, Przemyslaw Mielczarek, Dorota Lachowicz, Piotr Suder and Marek Smoluch
Materials 2023, 16(4), 1479; https://doi.org/10.3390/ma16041479 - 9 Feb 2023
Cited by 3 | Viewed by 2409
Abstract
Oocytes are a special kind of biological material. Here, the individual variability of a single cell is important. It means that the opportunity to obtain information about the lipid content from the analysis of a single cell is significant. In our study, we [...] Read more.
Oocytes are a special kind of biological material. Here, the individual variability of a single cell is important. It means that the opportunity to obtain information about the lipid content from the analysis of a single cell is significant. In our study, we present a method for lipid analysis based on the MALDI-based mass spectrometry imaging (MSI) approach. Our attention was paid to the sample preparation optimization with the aid of a wet-interface matrix deposition system (matrix spraying). Technical considerations of the sample preparation process, such as the number of matrix layers and the position of the spraying nozzle during the matrix deposition, are presented in the article. Additionally, we checked if changing the 2,5-dihydroxybenzoic acid (DHB) and 9-Aminoacridine (9AA) matrix concentration and their solvent composition may improve the analysis. Moreover, the comparison of paraformaldehyde-fixed versus nonfixed cell analysis was performed. We hope that our approach will be helpful for those working on lipid analyses in extraordinary material such as a single oocyte. Our study may also offer clues for anybody interested in single-cell analysis with the aid of MALDI mass spectrometry imaging and the wet-interface matrix deposition method. Full article
(This article belongs to the Special Issue Mass Spectrometry in Materials Science)
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10 pages, 3179 KB  
Article
Strong Plasmon-Mie Resonance in Si@Pd Core-Ω Shell Nanocavity
by Haomin Guo, Qi Hu, Chengyun Zhang, Haiwen Liu, Runmin Wu and Shusheng Pan
Materials 2023, 16(4), 1453; https://doi.org/10.3390/ma16041453 - 9 Feb 2023
Cited by 4 | Viewed by 3160
Abstract
The surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) can be used to enhance the generation of the hot electrons in plasmon metal nanocavity. In this paper, Pd nanomembrane (NMB) is sputtered on the surface of Si nanosphere (NS) on glass [...] Read more.
The surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) can be used to enhance the generation of the hot electrons in plasmon metal nanocavity. In this paper, Pd nanomembrane (NMB) is sputtered on the surface of Si nanosphere (NS) on glass substrate to form the Si@Pd core-Ω shell nanocavity. A plasmon-Mie resonance is induced in the nanocavity by coupling the plasmon resonance with the Mie resonance to control the optical property of Si NS. When this nanocavity is excited by near-infrared-1 (NIR-1, 650 nm–900 nm) femtosecond (fs) laser, the luminescence intensity of Si NS is dramatically enhanced due to the synergistic interaction of plasmon and Mie resonance. The generation of resonance coupling regulates resonant mode of the nanocavity to realize multi-dimensional nonlinear optical response, which can be utilized in the fields of biological imaging and nanoscale light source. Full article
(This article belongs to the Special Issue Synthesis and Application of Advanced Optical and Optoelectronic Functional Materials)
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12 pages, 2084 KB  
Article
Enhanced Thermoelectric Properties of Misfit Bi2Sr2-xCaxCo2Oy: Isovalent Substitutions and Selective Phonon Scattering
by Arindom Chatterjee, Ananya Banik, Alexandros El Sachat, José Manuel Caicedo Roque, Jessica Padilla-Pantoja, Clivia M. Sotomayor Torres, Kanishka Biswas, José Santiso and Emigdio Chavez-Angel
Materials 2023, 16(4), 1413; https://doi.org/10.3390/ma16041413 - 8 Feb 2023
Cited by 6 | Viewed by 2463
Abstract
Layered Bi-misfit cobaltates, such as Bi2Sr2Co2Oy, are the natural superlattice of an electrically insulating rocksalt (RS) type Bi2Sr2O4 layer and electrically conducting CoO2 layer, stacked along the crystallographic c-axis. [...] Read more.
Layered Bi-misfit cobaltates, such as Bi2Sr2Co2Oy, are the natural superlattice of an electrically insulating rocksalt (RS) type Bi2Sr2O4 layer and electrically conducting CoO2 layer, stacked along the crystallographic c-axis. RS and CoO2 layers are related through charge compensation reactions (or charge transfer). Therefore, thermoelectric transport properties are affected when doping or substitution is carried out in the RS layer. In this work, we have shown improved thermoelectric properties of spark plasma sintered Bi2Sr2-xCaxCo2Oy alloys (x = 0, 0.3 and 0.5). The substitution of Ca atoms affects the thermal properties by introducing point-defect phonon scattering, while the electronic conductivity and thermopower remain unaltered. Full article
(This article belongs to the Special Issue Thermoelectric Materials: Progress and Their Applications)
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22 pages, 8744 KB  
Article
Abnormal Eu3+ → Eu2+ Reduction in Ca9−xMnxEu(PO4)7 Phosphors: Structure and Luminescent Properties
by Elena V. Sipina, Dmitry A. Spassky, Nataliya R. Krutyak, Vladimir A. Morozov, Evgenia S. Zhukovskaya, Alexei A. Belik, Mikhail S. Manylov, Bogdan I. Lazoryak and Dina V. Deyneko
Materials 2023, 16(4), 1383; https://doi.org/10.3390/ma16041383 - 7 Feb 2023
Cited by 10 | Viewed by 2878
Abstract
β-Ca3(PO4)2-type phosphors Ca9−xMnxEu(PO4)7 have been synthesized by high-temperature solid-phase reactions. The crystal structure of Ca8MnEu(PO4)7 was characterized by synchrotron X-ray diffraction. The phase transitions, [...] Read more.
β-Ca3(PO4)2-type phosphors Ca9−xMnxEu(PO4)7 have been synthesized by high-temperature solid-phase reactions. The crystal structure of Ca8MnEu(PO4)7 was characterized by synchrotron X-ray diffraction. The phase transitions, magnetic and photoluminescence (PL) properties were studied. The abnormal reduction Eu3+ → Eu2+ in air was observed in Ca9−xMnxEu(PO4)7 according to PL spectra study and confirmed by X-ray photoelectron spectroscopy (XPS). Eu3+ shows partial reduction and coexistence of Eu2+/3+ states. It reflects in combination of a broad band from the Eu2+ 4f65d1 → 4f7 transition and a series of sharp lines attributed to 5D0 → 7FJ transitions of Eu3+. Eu2+/Eu3+ ions are redistributed among two crystal sites, M1 and M3, while Mn2+ fully occupies octahedral site M5 in Ca8MnEu(PO4)7. The main emission band was attributed to the 5D0 → 7F2 electric dipole transition of Eu3+ at 395 nm excitation. The abnormal quenching of Eu3+ emission was observed in Ca9−xMnxEu(PO4)7 phosphors with doping of the host by Mn2+ ions. The phenomena of abnormal reduction and quenching were discussed in detail. Full article
(This article belongs to the Special Issue Advanced Materials for Optical and Luminescence Applications)
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33 pages, 12603 KB  
Article
Application of the ps−Version of the Finite Element Method to the Analysis of Laminated Shells
by Cheng Angelo Yan and Riccardo Vescovini
Materials 2023, 16(4), 1395; https://doi.org/10.3390/ma16041395 - 7 Feb 2023
Cited by 4 | Viewed by 2187
Abstract
The development of accurate and efficient numerical methods is of crucial importance for the analysis and design of composite structures. This is even more true in the presence of variable stiffness (VS) configurations, where intricate load paths can be responsible for complex and [...] Read more.
The development of accurate and efficient numerical methods is of crucial importance for the analysis and design of composite structures. This is even more true in the presence of variable stiffness (VS) configurations, where intricate load paths can be responsible for complex and localized stress profiles. In this work, we present the ps−version of the finite elements method (ps−FEM), a novel FE approach which can perform global/local analysis through different refinement strategies efficiently and easily. Within this framework, the global behavior is captured through a p−refinement by increasing the polynomial order of the elements. For the local one, a mesh−superposition technique, called s−refinement, is used to improve locally the solution by defining a local/fine mesh overlaid to the global/coarse one. The combination of p− and s−refinements enables us to achieve excellent accuracy−to−cost ratios. This paper aims to present the numerical formulation and the implementation aspects of this novel approach to VS composite shell analysis. Numerical tests are reported to illustrate the potential of the method. The results provide a clear insight of its potential to guarantee fast convergence and easy mesh refinement where needed. Full article
(This article belongs to the Special Issue Feature Papers in Materials Simulation and Design)
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11 pages, 8368 KB  
Article
Novel Artificial Scaffold for Bone Marrow Regeneration: Honeycomb Tricalcium Phosphate
by Yasunori Inada, Kiyofumi Takabatake, Hidetsugu Tsujigiwa, Keisuke Nakano, Qiusheng Shan, Tianyan Piao, Anqi Chang, Hotaka Kawai and Hitoshi Nagatsuka
Materials 2023, 16(4), 1393; https://doi.org/10.3390/ma16041393 - 7 Feb 2023
Cited by 3 | Viewed by 2221
Abstract
Bone marrow is complex structure containing heterogenetic cells, making it difficult to regenerate using artificial scaffolds. In a previous study, we succeeded in developing honeycomb tricalcium phosphate (TCP), which is a cylindrical scaffold with a honeycomb arrangement of straight pores, and we demonstrated [...] Read more.
Bone marrow is complex structure containing heterogenetic cells, making it difficult to regenerate using artificial scaffolds. In a previous study, we succeeded in developing honeycomb tricalcium phosphate (TCP), which is a cylindrical scaffold with a honeycomb arrangement of straight pores, and we demonstrated that TCP with 300 and 500 μm pore diameters (300TCP and 500TCP) induced bone marrow structure within the pores. In this study, we examined the optimal scaffold structure for bone marrow with homeostatic bone metabolism using honeycomb TCP. 300TCP and 500TCP were transplanted into rat muscle, and bone marrow formation was histologically assessed. Immunohistochemistry for CD45, CD34, Runt-related transcription factor 2 (Runx2), c-kit single staining, Runx2/N-cadherin, and c-kit/Tie-2 double staining was performed. The area of bone marrow structure, which includes CD45(+) round-shaped hematopoietic cells and CD34(+) sinusoidal vessels, was larger in 300TCP than in 500TCP. Additionally, Runx2(+) osteoblasts and c-kit(+) hematopoietic stem cells were observed on the surface of bone tissue formed within TCP. Among Runx2(+) osteoblasts, spindle-shaped N-cadherin(+) cells existed in association with c-kit(+)Tie-2(+) hematopoietic stem cells on the bone tissue formed within TCP, which formed a hematopoietic stem cell niche similar to as in vivo. Therefore, honeycomb TCP with 300 μm pore diameters may be an artificial scaffold with an optimal geometric structure as a scaffold for bone marrow formation. Full article
(This article belongs to the Special Issue Materials for Hard Tissue Repair and Regeneration (Second Volume))
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13 pages, 1973 KB  
Article
Ultrafiltration Membranes Modified with Reduced Graphene Oxide: Effect on Methyl Green Removal from Aqueous Solution
by María Dolores Murcia, Asunción M. Hidalgo, María Gómez, Gerardo León, Elisa Gómez and Marta Martínez
Materials 2023, 16(4), 1369; https://doi.org/10.3390/ma16041369 - 6 Feb 2023
Cited by 2 | Viewed by 2569
Abstract
In this work, three types of ultrafiltration membranes with different characteristics (GR60PP, RC70PP and GR80PP) have been tested for the removal of the dye methyl green. The tests were first carried out with the three membranes without any modification and then with the [...] Read more.
In this work, three types of ultrafiltration membranes with different characteristics (GR60PP, RC70PP and GR80PP) have been tested for the removal of the dye methyl green. The tests were first carried out with the three membranes without any modification and then with the membranes’ surfaces modified with reduced graphene oxide (rGO). The modification was achieved through physical treatment. The CR70PP membrane did not support the modification treatment and was discarded. The other membranes were initially characterized with distilled water tests to study the permeability to the solvent, and later, the permeate fluxes and the values of rejection coefficients were obtained at different working pressures with a fixed dye initial concentration. In addition, SEM images and SEM-EDX spectra of the native and modified membranes were obtained before and after the dye tests. The GR60PP membrane has shown the best results in relation to the modification because it has increased its rejection levels. On the opposite, the GR80PP membrane performs better without surface modification, achieving the highest rejection values and the highest permeate fluxes in its native form. Full article
(This article belongs to the Special Issue Development and Application of Novel Membranes)
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24 pages, 9738 KB  
Article
Mechanical Behavior of Austenitic Steel under Multi-Axial Cyclic Loading
by Abhishek Biswas, Dzhem Kurtulan, Timothy Ngeru, Abril Azócar Guzmán, Stefanie Hanke and Alexander Hartmaier
Materials 2023, 16(4), 1367; https://doi.org/10.3390/ma16041367 - 6 Feb 2023
Cited by 2 | Viewed by 2390
Abstract
Low-nickel austenitic steel is subjected to high-pressure torsion fatigue (HPTF) loading, where a constant axial compression is overlaid with a cyclic torsion. The focus of this work lies on investigating whether isotropic J2 plasticity or crystal plasticity can describe the mechanical behavior during [...] Read more.
Low-nickel austenitic steel is subjected to high-pressure torsion fatigue (HPTF) loading, where a constant axial compression is overlaid with a cyclic torsion. The focus of this work lies on investigating whether isotropic J2 plasticity or crystal plasticity can describe the mechanical behavior during HPTF loading, particularly focusing on the axial creep deformation seen in the experiment. The results indicate that a J2 plasticity model with an associated flow rule fails to describe the axial creep behavior. In contrast, a micromechanical model based on an empirical crystal plasticity law with kinematic hardening described by the Ohno–Wang rule can match the HPTF experiments quite accurately. Hence, our results confirm the versatility of crystal plasticity in combination with microstructural models to describe the mechanical behavior of materials under reversing multiaxial loading situations. Full article
(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)
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16 pages, 3980 KB  
Article
A Numerical Model for Understanding the Development of Adhesion during Drying of Cellulose Model Surfaces
by Magdalena Kaplan and Sören Östlund
Materials 2023, 16(4), 1327; https://doi.org/10.3390/ma16041327 - 4 Feb 2023
Cited by 2 | Viewed by 1973
Abstract
Adhesion is crucial for the development of mechanical properties in fibre-network materials, such as paper or other cellulose fibre biocomposites. The stress transfer within the network is possible through the fibre–fibre joints, which develop their strength during drying. Model surfaces are useful for [...] Read more.
Adhesion is crucial for the development of mechanical properties in fibre-network materials, such as paper or other cellulose fibre biocomposites. The stress transfer within the network is possible through the fibre–fibre joints, which develop their strength during drying. Model surfaces are useful for studying the adhesive strength of joints by excluding other parameters influencing global performance, such as geometry, fibre fibrillation, or surface roughness. Here, a numerical model describes the development of adhesion between a cellulose bead and a rigid surface using an axisymmetric formulation, including moisture diffusion, hygroexpansion, and cohesive surfaces. It is useful for studying the development of stresses during drying. A calibration of model parameters against previously published contact and geometry measurements shows that the model can replicate the observed behaviour. A parameter study shows the influence of cohesive and material parameters on the contact area. The developed model opens possibilities for further studies on model surfaces, with quantification of the adhesion during pull-off measurements. Full article
(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)
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12 pages, 6105 KB  
Article
Novel Ultrafine-Grain Mg-Gd/Nd-Y-Ca Alloys with an Increased Ignition Temperature
by Stanislav Šašek, Peter Minárik, Jitka Stráská, Klára Hosová, Jozef Veselý, Jiří Kubásek, Robert Král, Tomáš Krajňák and Dalibor Vojtěch
Materials 2023, 16(3), 1299; https://doi.org/10.3390/ma16031299 - 3 Feb 2023
Cited by 11 | Viewed by 2817
Abstract
Two novel ignition-resistant magnesium alloys, Mg-2Gd-2Y-1Ca and Mg-2Nd-1Y-1Ca, were prepared in the ultrafine-grain condition by equal channel angular pressing (ECAP). In addition, four commercial alloys—AZ31, AX41, AE42 and WE43—were prepared similarly as a reference. The microstructure, mechanical properties and ignition temperature were thoroughly [...] Read more.
Two novel ignition-resistant magnesium alloys, Mg-2Gd-2Y-1Ca and Mg-2Nd-1Y-1Ca, were prepared in the ultrafine-grain condition by equal channel angular pressing (ECAP). In addition, four commercial alloys—AZ31, AX41, AE42 and WE43—were prepared similarly as a reference. The microstructure, mechanical properties and ignition temperature were thoroughly investigated. Both novel alloys exhibited a mean grain size of ~1 µm and dense distribution of small secondary phase particles. The mechanical strength measured by the tensile deformation test showed that the novel alloys are much stronger (~290 MPa) than all commercial alloys except WE43. However, Ca segregation into the grain boundaries caused a significant decrease in ductility (<6%). The ignition temperature of the novel alloys (~950 °C) was considerably improved by the presence of Gd/Nd, Y and Ca. This study showed that both novel alloys exhibit high strength and high ignition temperature in the ultrafine-grain condition. Full article
(This article belongs to the Section Metals and Alloys)
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11 pages, 5394 KB  
Article
Optical Properties Investigation of Upconverting K2Gd(PO4)(WO4):20%Yb3+,Tm3+ Phosphors
by Julija Grigorjevaite and Arturas Katelnikovas
Materials 2023, 16(3), 1305; https://doi.org/10.3390/ma16031305 - 3 Feb 2023
Cited by 5 | Viewed by 2272
Abstract
Nowadays, scientists are interested in inorganic luminescence materials that can be excited with UV or NIR radiation and emit in the visible range. Such inorganic materials can be successfully used as luminescent or anti-counterfeiting pigments. In this work, we report the synthesis and [...] Read more.
Nowadays, scientists are interested in inorganic luminescence materials that can be excited with UV or NIR radiation and emit in the visible range. Such inorganic materials can be successfully used as luminescent or anti-counterfeiting pigments. In this work, we report the synthesis and optical properties investigation of solely Tm3+ doped and Yb3+/Tm3+ co-doped K2Gd(PO4)(WO4) phosphors. The single-phase samples were prepared using a solid-state reaction method. The Tm3+ concentration was changed from 0.5% to 5%. Downshifting and upconversion emission studies were performed under 360 nm and 980 nm excitation, respectively. Yb3+ ions were used as sensitizers in the K2Gd(PO4)(WO4) phosphors to transfer the captured energy to Tm3+ ions. It turned out that under UV excitation, phosphors emitted in the blue spectral area regardless of the presence or absence of Yb3+. However, a very strong deep-red (~800 nm) emission was observed when Yb3+ and Tm3+-containing samples were excited with a 980 nm wavelength laser. It is interesting that the highest upconversion emission in the UV/Visible range was achieved for 20% Yb3+, 0.5% Tm3+ doped sample, whereas the sample co-doped with 20% Yb3+, 2% Tm3+ showed the most intensive UC emission band in the NIR range. The materials were characterized using powder X-ray diffraction and scanning electron microscopy. Optical properties were studied using steady-state and kinetic downshifting and upconversion photoluminescence spectroscopy. Full article
(This article belongs to the Special Issue Functional Inorganic Materials: Preparation, Characterization and Application)
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14 pages, 6711 KB  
Article
Thermal Diffusivity of Concrete Samples Assessment Using a Solar Simulator
by Marcin Bilski, Przemysław Górnaś, Andrzej Pożarycki, Przemysław Skrzypczak, Mieczysław Słowik, Marta Mielczarek, Agnieszka Wróblewska and Łukasz Semkło
Materials 2023, 16(3), 1268; https://doi.org/10.3390/ma16031268 - 2 Feb 2023
Cited by 4 | Viewed by 2161
Abstract
The thermal properties of pavement layers made of concrete with varying bulk densities are a particularly interesting topic in the context of development road technologies. If a hybrid layer system is used as a starting point, with thin asphalt layers (from 1 cm [...] Read more.
The thermal properties of pavement layers made of concrete with varying bulk densities are a particularly interesting topic in the context of development road technologies. If a hybrid layer system is used as a starting point, with thin asphalt layers (from 1 cm to 4 cm) laid on top of a foam concrete layer, thermal properties begin to play a crucial role. The main research problem was to create a test method enabling the assessment of the influence of solar heating on the thermal parameters of the building material, especially cement concrete. For this reason, this paper is concerned specifically with the assessment of a new methodology for testing and calculating the value of the thermal diffusivity coefficient of samples made of concrete varying bulk densities. In this case, using the proprietary concept the authors built a solar simulator using a multi-source lighting system. The analysis of the results of laboratory tests and numerical analyses allowed the authors to observe that there is a strong correlation between the bulk density of samples heated and the thermal diffusivity parameter, which appears in the unidirectional heat transfer equation. The strength of this relationship has been expressed with the coefficient of determination and amounts to 99%. The calculated values of the coefficient of thermal diffusivity for samples made of foam concrete range from 0.16×10−6m2s to 0.52×10−6m2s and are lower (from 2.5 to 8 times) than the value determined for samples made of typical cement concrete. Full article
(This article belongs to the Section Construction and Building Materials)
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15 pages, 5074 KB  
Article
The Influence of Annealing at 500 and 900 °C on the Structure and Mechanical Properties of AlxCoCrFeNi Alloys
by Marzena Tokarewicz, Małgorzata Grądzka-Dahlke, Katarzyna Rećko and Magdalena Łępicka
Materials 2023, 16(3), 1245; https://doi.org/10.3390/ma16031245 - 1 Feb 2023
Cited by 9 | Viewed by 2210
Abstract
The AlCoCrFeNi high-entropy alloy is sensitive to heat treatment. The aim of the present study was to test a similar correlation for AlxCoCrFeNi alloys with less than equimolar aluminum content. This paper presents a study of the annealing effect on the [...] Read more.
The AlCoCrFeNi high-entropy alloy is sensitive to heat treatment. The aim of the present study was to test a similar correlation for AlxCoCrFeNi alloys with less than equimolar aluminum content. This paper presents a study of the annealing effect on the structure and mechanical properties of selected alloys. AlxCoCrFeNi alloys (x = 0, 0.5, 0.7) were fabricated by the induction melting method. The obtained specimens were annealed at 500 °C and 900 °C. A detailed study of the changes in crystalline structure due to annealing was conducted. Three-point bending and hardness tests were carried out for the as-cast and annealed specimens to determine selected mechanical properties. The study confirmed that increasing the aluminum content in the AlxCoCrFeNi alloy improves mechanical properties. For the alloy with aluminum content x = 0.7, hardness increased by 187% and yield strength by 252% compared to the alloy without aluminum. A significant effect of annealing on the crystalline structure of the Al0.7CoCrFeNi alloy was found, but this was not followed by changes in mechanical properties. Full article
(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)
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11 pages, 4011 KB  
Article
Short-Term Memory Characteristics of IGZO-Based Three-Terminal Devices
by Juyeong Pyo, Jong-Ho Bae, Sungjun Kim and Seongjae Cho
Materials 2023, 16(3), 1249; https://doi.org/10.3390/ma16031249 - 1 Feb 2023
Cited by 8 | Viewed by 3044
Abstract
A three-terminal synaptic transistor enables more accurate controllability over the conductance compared with traditional two-terminal synaptic devices for the synaptic devices in hardware-oriented neuromorphic systems. In this work, we fabricated IGZO-based three-terminal devices comprising HfAlOx and CeOx layers to demonstrate the [...] Read more.
A three-terminal synaptic transistor enables more accurate controllability over the conductance compared with traditional two-terminal synaptic devices for the synaptic devices in hardware-oriented neuromorphic systems. In this work, we fabricated IGZO-based three-terminal devices comprising HfAlOx and CeOx layers to demonstrate the synaptic operations. The chemical compositions and thicknesses of the devices were verified by transmission electron microscopy and energy dispersive spectroscopy in cooperation. The excitatory post-synaptic current (EPSC), paired-pulse facilitation (PPF), short-term potentiation (STP), and short-term depression (STD) of the synaptic devices were realized for the short-term memory behaviors. The IGZO-based three-terminal synaptic transistor could thus be controlled appropriately by the amplitude, width, and interval time of the pulses for implementing the neuromorphic systems. Full article
(This article belongs to the Special Issue Advances in Conducting and Semiconducting Materials)
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13 pages, 4705 KB  
Article
Freeze Drying of Polymer Nanoparticles and Liposomes Exploiting Different Saccharide-Based Approaches
by Ilaria Andreana, Valeria Bincoletto, Maela Manzoli, Francesca Rodà, Vita Giarraputo, Paola Milla, Silvia Arpicco and Barbara Stella
Materials 2023, 16(3), 1212; https://doi.org/10.3390/ma16031212 - 31 Jan 2023
Cited by 33 | Viewed by 9056
Abstract
Biodegradable nanocarriers represent promising tools for controlled drug delivery. However, one major drawback related to their use is the long-term stability, which is largely influenced by the presence of water in the formulations, so to solve this problem, freeze-drying with cryoprotectants has been [...] Read more.
Biodegradable nanocarriers represent promising tools for controlled drug delivery. However, one major drawback related to their use is the long-term stability, which is largely influenced by the presence of water in the formulations, so to solve this problem, freeze-drying with cryoprotectants has been proposed. In the present study, the influence of the freeze-drying procedure on the storage stability of poly(lactide-co-glycolide) (PLGA) nanoparticles and liposomes was evaluated. In particular, conventional cryoprotectants were added to PLGA nanoparticle and liposome formulations in various conditions. Additionally, hyaluronic acid (HA), known for its ability to target the CD44 receptor, was assessed as a cryoprotective excipient: it was added to the nanocarriers as either a free molecule or conjugated to a phospholipid to increase the interaction with the polymer or lipid matrix while exposing HA on the nanocarrier surface. The formulations were resuspended and characterized for size, polydispersity index, zeta potential and morphology. It was demonstrated that only the highest percentages of cryoprotectants allowed the resuspension of stable nanocarriers. Moreover, unlike free HA, HA-phospholipid conjugates were able to maintain the particle mean size after the reconstitution of lyophilized nanoparticles and liposomes. This study paves the way for the use of HA-phospholipids to achieve, at the same time, nanocarrier cryoprotection and active targeting. Full article
(This article belongs to the Special Issue Nanomaterials Design towards Biomedical Applications (Volume II))
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12 pages, 2797 KB  
Article
Polarization Doping in a GaN-InN System—Ab Initio Simulation
by Ashfaq Ahmad, Pawel Strak, Pawel Kempisty, Konrad Sakowski, Jacek Piechota, Yoshihiro Kangawa, Izabella Grzegory, Michal Leszczynski, Zbigniew R. Zytkiewicz, Grzegorz Muziol, Eva Monroy, Agata Kaminska and Stanislaw Krukowski
Materials 2023, 16(3), 1227; https://doi.org/10.3390/ma16031227 - 31 Jan 2023
Viewed by 2807
Abstract
Polarization doping in a GaN-InN system with a graded composition layer was studied using ab initio simulations. The electric charge volume density in the graded concentration part was determined by spatial potential dependence. The emerging graded polarization charge was determined to show that [...] Read more.
Polarization doping in a GaN-InN system with a graded composition layer was studied using ab initio simulations. The electric charge volume density in the graded concentration part was determined by spatial potential dependence. The emerging graded polarization charge was determined to show that it could be obtained from a polarization difference and the concentration slope. It was shown that the GaN-InN polarization difference is changed by piezoelectric effects. The polarization difference is in agreement with the earlier obtained data despite the relatively narrow bandgap for the simulated system. The hole generation may be applied in the design of blue and green laser and light-emitting diodes. Full article
(This article belongs to the Special Issue III-V Semiconductor Optoelectronics: Materials and Devices)
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21 pages, 5853 KB  
Article
Physicochemical Modeling of Electrochemical Impedance in Solid-State Supercapacitors
by Davood Peyrow Hedayati, Gita Singh, Michael Kucher, Tony D. Keene and Robert Böhm
Materials 2023, 16(3), 1232; https://doi.org/10.3390/ma16031232 - 31 Jan 2023
Cited by 9 | Viewed by 4456
Abstract
Solid-state supercapacitors (SSCs) consist of porous carbon electrodes and gel-polymer electrolytes and are used in novel energy storage applications. The current study aims to simulate the impedance of SSCs using a clearly defined equivalent circuit (EC) model with the ultimate goal of improving [...] Read more.
Solid-state supercapacitors (SSCs) consist of porous carbon electrodes and gel-polymer electrolytes and are used in novel energy storage applications. The current study aims to simulate the impedance of SSCs using a clearly defined equivalent circuit (EC) model with the ultimate goal of improving their performance. To this end, a conventional mathematical and a physicochemical model were adapted. The impedance was measured by electrochemical impedance spectroscopy (EIS). An EC consisting of electrical elements was introduced for each modeling approach. The mathematical model was purely based on a best-fit method and utilized an EC with intuitive elements. In contrast, the physicochemical model was motivated by advanced theories and allowed meaningful associations with properties at the electrode, the electrolyte, and their interface. The physicochemical model showed a higher approximation ability (relative error of 3.7%) due to the interface impedance integration in a more complex circuit design. However, this model required more modeling and optimization effort. Moreover, the fitted parameters differed from the analytically calculated ones due to uncertainties in the SSC’s microscale configuration, which need further investigations. Nevertheless, the results show that the proposed physicochemical model is promising in simulating EIS data of SSCs with the additional advantage of utilizing well-reasoned property-based EC elements. Full article
(This article belongs to the Special Issue New-Generation Advanced Materials for Next-Generation Supercapacitors)
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18 pages, 2394 KB  
Article
The Morphology, Mechanical and Dynamic Properties, Fire Hazard and Toxicity of Chloroprene and Butadiene Rubber Composites Cross-Linked with Zinc
by Aleksandra Smejda-Krzewicka, Przemysław Rybiński, Dariusz Bradło and Witold Żukowski
Materials 2023, 16(3), 1240; https://doi.org/10.3390/ma16031240 - 31 Jan 2023
Cited by 5 | Viewed by 2218
Abstract
This paper presents the influence of zinc on the cross-linking process, mechanical and dynamic properties, morphologies and balance of thermal degradation of blends containing chloroprene rubber (CR) and butadiene rubber (BR). The novel aspect of this research is a comprehensive approach presenting a [...] Read more.
This paper presents the influence of zinc on the cross-linking process, mechanical and dynamic properties, morphologies and balance of thermal degradation of blends containing chloroprene rubber (CR) and butadiene rubber (BR). The novel aspect of this research is a comprehensive approach presenting a new curing agent for the CR/BR blends to increase their cross-linking density and final properties, including non-flammability and low fire hazard. This is due to the need to find an alternative to zinc oxide, which is the standard curing agent for chloroprene rubber. The regulations of the European Union enforce a significant limitation on the use of this compound in elastomer technology, due to its harmful effect on aquatic organisms. In this paper, the CR/BR composites were cured with zinc and filled with natural silica fillers (sillitin or chalcedonite) or synthetic silica filler (aerosil). The investigation focused on the morphology characterization of the obtained compounds, their cross-linking degree, swelling, mechanical and dynamic properties, fire hazard and toxicity. The structure of cured CR/BR blends was characterized via scanning electron microscopy (SEM). The fire resistance studies were performed using cone calorimetry or oxygen index methods, whereas toxicity tests were performed with the use of the FB-FTIR (fluidized bed reactor coupled with FTIR analyzer) method. The results showed that obtained CR/BR products were characterized by satisfactory final properties. The properties determined by the oxygen index and cone calorimetry methods, including the behaviors of the tested CR/BR vulcanizates in fire conditions, showed that the produced compounds were characterized by a low fire hazard and can be classified as non-combustible rubber products. However, the toxicity of the decomposition products, determined at 450, 550 and 750 °C, was very high. Full article
(This article belongs to the Special Issue Morphology, Flammability, Thermal and Mechanical Properties of Polymer Composites)
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14 pages, 18830 KB  
Article
MoS2/Au Heterojunction Catalyst for SERS Monitoring of a Fenton-like Reaction
by Qian Wei, Beibei Lu, Qing Yang, Can Shi, Yulan Wei, Minmin Xu, Chenjie Zhang and Yaxian Yuan
Materials 2023, 16(3), 1169; https://doi.org/10.3390/ma16031169 - 30 Jan 2023
Cited by 1 | Viewed by 2921
Abstract
Fenton technology is one of advanced oxidation process (AOP) methods to treat wastewater through chemical oxidation. Due to the limitations of classical iron-based catalysts, it is still challenging to find suitable catalysts for Fenton-like reactions. Here, MoS2/Au heterojunctions were successfully synthesized [...] Read more.
Fenton technology is one of advanced oxidation process (AOP) methods to treat wastewater through chemical oxidation. Due to the limitations of classical iron-based catalysts, it is still challenging to find suitable catalysts for Fenton-like reactions. Here, MoS2/Au heterojunctions were successfully synthesized by reduction of chloroauric acid in the solution of layered MoS2 prepared by hydrothermal method. As a model molecule, methylene blue (MB) was used as the species to be degraded to evaluate the performance of the catalyst. It was determined by UV–visible spectra that the optimal catalyst can be obtained when MoS2 (mg): HAuCl4 (wt. % mL) is 2:2. The Fenton-like reaction process was monitored by introducing highly sensitive surface enhanced Raman spectroscopy (SERS). The results show that MB can be degraded by 83% in the first 10 min of the reaction, indicating that MoS2/Au has good catalytic performance. In addition, as a fingerprint spectrum, SERS was used to preliminarily analyze the molecular structure changes during the degradation process. The result showed that C-N-C bond was easier to break than the C-S-C bond. NH2 group and the fused ring were destroyed at the comparable speed at the first 30 min. In terms of application applicability, it was showed that MB degradation had exceeded 95% at all the three pH values of 1.4, 5.0, and 11.1 after the reaction was carried out for 20 min. The test and analysis of the light environment showed that the catalytic efficiency was significantly improved in the natural light of the laboratory compared to dark conditions. The possible mechanism based on ·OH and ·O2− from ESR data was proposed. In addition, it was demonstrated to be a first-order reaction from the perspective of kinetics. This study made a positive contribution to broaden of the applicable conditions and scope of Fenton-like reaction catalysts. It is expected to be used as a non-iron catalyst in practical industrial applications. From the perspective of detection method, we expect to develop SERS as a powerful tool for the in situ monitoring of Fenton-like reactions, and to further deepen our understanding of the mechanism. Full article
(This article belongs to the Special Issue Advanced Photocatalytic Material: Synthesis, Characterization and Application)
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19 pages, 7258 KB  
Article
Reinforcement Corrosion Testing in Concrete and Fiber Reinforced Concrete Specimens Exposed to Aggressive External Factors
by Wioletta Raczkiewicz, Magdalena Bacharz, Kamil Bacharz and Michał Teodorczyk
Materials 2023, 16(3), 1174; https://doi.org/10.3390/ma16031174 - 30 Jan 2023
Cited by 13 | Viewed by 3590
Abstract
One of the leading causes of reinforced concrete degradation is chloride attack. It occurs due to the penetration of chlorides through pores and cracks into the concrete cover. This phenomenon becomes more dangerous if reinforced concrete elements are subjected to cyclic temperature changes. [...] Read more.
One of the leading causes of reinforced concrete degradation is chloride attack. It occurs due to the penetration of chlorides through pores and cracks into the concrete cover. This phenomenon becomes more dangerous if reinforced concrete elements are subjected to cyclic temperature changes. The concrete cover protects against corrosion. This paper presents research, the primary purpose of which was to determine the effect of the addition of steel fibers to concrete on the development of corrosion of the main reinforcement. The tests were carried out on three types of reinforced concrete specimens made of ordinary concrete and concrete with different amounts of steel fibers (0.25% and 0.50%). In order to initiate corrosion processes, specimens were partially submerged in a 3% sodium chloride solution and were subjected to freeze–thaw cycles. The electrochemical polarization galvanostatic pulse method was used for analyzing the reinforcement corrosion activity. Moreover, it was verified whether the corrosion of reinforced concrete elements affects the acoustic emission wave velocity. The addition of steel micro-reinforcement fibers increases the corrosion resistance of reinforced concrete. In addition, a strong linear correlation between the AE wave velocity and the values of the corrosion current density was revealed. Full article
(This article belongs to the Special Issue Corrosion of Materials: Evaluation, Testing, Protection, and Failure Analysis)
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24 pages, 3728 KB  
Article
Effects of Altering Magnesium Metal Surfaces on Degradation In Vitro and In Vivo during Peripheral Nerve Regeneration
by Rigwed Tatu, Leon G. White, Yeoheung Yun, Tracy Hopkins, Xiaoxian An, Ahmed Ashraf, Kevin J. Little, Meir Hershcovitch, David B. Hom and Sarah Pixley
Materials 2023, 16(3), 1195; https://doi.org/10.3390/ma16031195 - 30 Jan 2023
Cited by 6 | Viewed by 3147
Abstract
In vivo use of biodegradable magnesium (Mg) metal can be plagued by too rapid a degradation rate that removes metal support before physiological function is repaired. To advance the use of Mg biomedical implants, the degradation rate may need to be adjusted. We [...] Read more.
In vivo use of biodegradable magnesium (Mg) metal can be plagued by too rapid a degradation rate that removes metal support before physiological function is repaired. To advance the use of Mg biomedical implants, the degradation rate may need to be adjusted. We previously demonstrated that pure Mg filaments used in a nerve repair scaffold were compatible with regenerating peripheral nerve tissues, reduced inflammation, and improved axonal numbers across a short—but not long—gap in sciatic nerves in rats. To determine if the repair of longer gaps would be improved by a slower Mg degradation rate, we tested, in vitro and in vivo, the effects of Mg filament polishing followed by anodization using plasma electrolytic oxidation (PEO) with non-toxic electrolytes. Polishing removed oxidation products from the surface of as-received (unpolished) filaments, exposed more Mg on the surface, produced a smoother surface, slowed in vitro Mg degradation over four weeks after immersion in a physiological solution, and improved attachment of cultured epithelial cells. In vivo, treated Mg filaments were used to repair longer (15 mm) injury gaps in adult rat sciatic nerves after placement inside hollow poly (caprolactone) nerve conduits. The addition of single Mg or control titanium filaments was compared to empty conduits (negative control) and isografts (nerves from donor rats, positive control). After six weeks in vivo, live animal imaging with micro computed tomography (micro-CT) showed that Mg metal degradation rates were slowed by polishing vs. as-received Mg, but not by anodization, which introduced greater variability. After 14 weeks in vivo, functional return was seen only with isograft controls. However, within Mg filament groups, the amount of axonal growth across the injury site was improved with slower Mg degradation rates. Thus, anodization slowed degradation in vitro but not in vivo, and degradation rates do affect nerve regeneration. Full article
(This article belongs to the Special Issue Magnesium and Its Alloys as Biodegradable Implants)
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16 pages, 2471 KB  
Article
Phenolic Compounds Removal from Olive Mill Wastewater Using the Composite of Activated Carbon and Copper-Based Metal-Organic Framework
by Muna A. Abu-Dalo, Nathir A. F. Al-Rawashdeh, Moath Almurabi, Jehad Abdelnabi and Abeer Al Bawab
Materials 2023, 16(3), 1159; https://doi.org/10.3390/ma16031159 - 29 Jan 2023
Cited by 11 | Viewed by 3616
Abstract
As the industry of olive oil continues to grow, the management of olive mill wastewater (OMW) by-products has become an area of great interest. While many strategies for processing OMW have been established, more studies are still required to find an effective adsorbent [...] Read more.
As the industry of olive oil continues to grow, the management of olive mill wastewater (OMW) by-products has become an area of great interest. While many strategies for processing OMW have been established, more studies are still required to find an effective adsorbent for total phenolic content uptake. Here, we present a composite of a Cu 1,4-benzene dicarboxylate metal-organic framework (Cu (BDC) MOF) and granular activated carbon (GAC) as an adsorbent for total phenolic content removal from OMW. Experimental results demonstrated that the maximum adsorption capacity was 20 mg/g of total phenolic content (TPC) after 4 h. using 2% wt/wt of GAC/Cu (BDC) MOF composite to OMW at optimum conditions (pH of 4.0 and 25 °C). The adsorption of phenolic content onto the GAC/Cu (BDC) MOF composite was described by the Freundlich adsorption and pseudo-second-order reaction. The adsorption reaction was found to be spontaneous and endothermic at 298 K where ΔS° and ΔH° were found to be 0.105 KJ/mol and 25.7 kJ/mol, respectively. While ΔGº value was −5.74 (kJ/mol). The results of this study provide a potential solution for the local and worldwide olive oil industry. Full article
(This article belongs to the Special Issue Recent Progress in Advanced Adsorption Materials)
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Article
Burdock-Derived Composites Based on Biogenic Gold, Silver Chloride and Zinc Oxide Particles as Green Multifunctional Platforms for Biomedical Applications and Environmental Protection
by Irina Zgura, Nicoleta Badea, Monica Enculescu, Valentin-Adrian Maraloiu, Camelia Ungureanu and Marcela-Elisabeta Barbinta-Patrascu
Materials 2023, 16(3), 1153; https://doi.org/10.3390/ma16031153 - 29 Jan 2023
Cited by 11 | Viewed by 3359
Abstract
Green nanotechnology is a rapidly growing field linked to using the principles of green chemistry to design novel nanomaterials with great potential in environmental and health protection. In this work, metal and semiconducting particles (AuNPs, AgClNPs, ZnO, AuZnO, AgClZnO, and AuAgClZnO) were phytosynthesized [...] Read more.
Green nanotechnology is a rapidly growing field linked to using the principles of green chemistry to design novel nanomaterials with great potential in environmental and health protection. In this work, metal and semiconducting particles (AuNPs, AgClNPs, ZnO, AuZnO, AgClZnO, and AuAgClZnO) were phytosynthesized through a “green” bottom-up approach, using burdock (Arctium lappa L.) aqueous extract. The morphological (SEM/TEM), structural (XRD, SAED), compositional (EDS), optical (UV–Vis absorption and FTIR spectroscopy), photocatalytic, and bio-properties of the prepared composites were analyzed. The particle size was determined by SEM/TEM and by DLS measurements. The phytoparticles presented high and moderate physical stability, evaluated by zeta potential measurements. The investigation of photocatalytic activity of these composites, using Rhodamine B solutions’ degradation under solar light irradiation in the presence of prepared powders, showed different degradation efficiencies. Bioevaluation of the obtained composites revealed the antioxidant and antibacterial properties. The tricomponent system AuAgClZnO showed the best antioxidant activity for capturing ROS and ABTS•+ radicals, and the best biocidal action against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The “green” developed composites can be considered potential adjuvants in biomedical (antioxidant or biocidal agents) or environmental (as antimicrobial agents and catalysts for degradation of water pollutants) applications. Full article
(This article belongs to the Special Issue Novel Green Nanotechnologies Applied in Environmental Protection and Health)
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