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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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35 pages, 4084 KiB  
Article
Electrostatically Interacting Wannier Qubits in Curved Space
by Krzysztof Pomorski
Materials 2024, 17(19), 4846; https://doi.org/10.3390/ma17194846 - 30 Sep 2024
Viewed by 918
Abstract
A derivation of a tight-binding model from Schrödinger formalism for various topologies of position-based semiconductor qubits is presented in the case of static and time-dependent electric fields. The simplistic tight-binding model enables the description of single-electron devices at a large integration scale. The [...] Read more.
A derivation of a tight-binding model from Schrödinger formalism for various topologies of position-based semiconductor qubits is presented in the case of static and time-dependent electric fields. The simplistic tight-binding model enables the description of single-electron devices at a large integration scale. The case of two electrostatically Wannier qubits (also known as position-based qubits) in a Schrödinger model is presented with omission of spin degrees of freedom. The concept of programmable quantum matter can be implemented in the chain of coupled semiconductor quantum dots. Highly integrated and developed cryogenic CMOS nanostructures can be mapped to coupled quantum dots, the connectivity of which can be controlled by a voltage applied across the transistor gates as well as using an external magnetic field. Using the anti-correlation principle arising from the Coulomb repulsion interaction between electrons, one can implement classical and quantum inverters (Classical/Quantum Swap Gate) and many other logical gates. The anti-correlation will be weakened due to the fact that the quantumness of the physical process brings about the coexistence of correlation and anti-correlation at the same time. One of the central results presented in this work relies on the appearance of dissipation-like processes and effective potential renormalization building effective barriers in both semiconductors and in superconductors between not bended nanowire regions both in classical and in quantum regimes. The presence of non-straight wire regions is also expressed by the geometrical dissipative quantum Aharonov–Bohm effect in superconductors/semiconductors when one obtains a complex value vector potential-like field. The existence of a Coulomb interaction provides a base for the physical description of an electrostatic Q-Swap gate with any topology using open-loop nanowires, with programmable functionality. We observe strong localization of the wavepacket due to nanowire bending. Therefore, it is not always necessary to build a barrier between two nanowires to obtain two quantum dot systems. On the other hand, the results can be mapped to the problem of an electron in curved space, so they can be expressed with a programmable position-dependent metric embedded in Schrödinger’s equation. The semiconductor quantum dot system is capable of mimicking curved space, providing a bridge between fundamental and applied science in the implementation of single-electron devices. Full article
(This article belongs to the Section Quantum Materials)
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13 pages, 5692 KiB  
Article
Experimental Investigation of the Impact of Loading Conditions on the Change in Thin NiTi Wire Resistance during Cyclic Stretching
by Jonasz Hartwich, Sławomir Duda, Sebastian Sławski, Marek Kciuk, Anna Woźniak and Grzegorz Gembalczyk
Materials 2024, 17(18), 4577; https://doi.org/10.3390/ma17184577 - 18 Sep 2024
Viewed by 696
Abstract
This paper presents the results of an experimental study designed to evaluate the effect of repeated stretching cycles on the electrical resistance change in a NiTi alloy wire. In particular, tests were carried out to determine the effect of the type of loading [...] Read more.
This paper presents the results of an experimental study designed to evaluate the effect of repeated stretching cycles on the electrical resistance change in a NiTi alloy wire. In particular, tests were carried out to determine the effect of the type of loading on resistance change in the investigated wires. Wires with a diameter of 100 μm were used in the research. The experiment was carried out on a dedicated test stand designed for this purpose. During the test, the samples were subjected to 40 identical tensile cycles. The electrical resistance, sample elongation, and tensile force during successive stretching cycles were measured. The conducted research demonstrated the impact of elongation and reorientation of the structure on the resistance change in NiTi alloy thin wires. The research included a comparison of the effect of two different types of loading on the electrical resistance change in the sample. During cyclic stretching of a NiTi alloy sample with constant displacement, a decrease in electrical resistance was observed after each successive stretching cycle. Alternatively, when stretching with a constant force, the value of electrical resistance increased. In both types of loads, the greatest change in resistance value was observed at the initial cycles. Full article
(This article belongs to the Special Issue Technology and Applications of Shape Memory Materials)
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20 pages, 7162 KiB  
Article
Homogenization of Thermal Properties in Metaplates
by David Faraci and Claudia Comi
Materials 2024, 17(18), 4557; https://doi.org/10.3390/ma17184557 - 17 Sep 2024
Viewed by 650
Abstract
Three-dimensional metamaterials endowed with two-dimensional in-plane periodicity exhibit peculiar thermoelastic behaviour when heated or cooled. By proper design of the unit cell, the equivalent thermal expansion coefficient can be programmed and can also reach negative values. The heterogeneity in the third direction of [...] Read more.
Three-dimensional metamaterials endowed with two-dimensional in-plane periodicity exhibit peculiar thermoelastic behaviour when heated or cooled. By proper design of the unit cell, the equivalent thermal expansion coefficient can be programmed and can also reach negative values. The heterogeneity in the third direction of such metamaterials also causes, in general, a thermal-induced deflection. The prediction of the equivalent thermal properties is important to design the metamaterial suitable for a specific application. Under the hypothesis of small thickness with respect to the global in-plane dimensions, we make use of asymptotic homogenization to describe the thermoelastic behaviour of these metamaterials as that of an equivalent homogenous plate. The method provides explicit expressions for the effective thermal properties, which allow for a cost-effective prediction of the thermoelastic response of these metaplates. Full article
(This article belongs to the Special Issue Advanced Mechanical Design and Applications of Metamaterials)
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62 pages, 16763 KiB  
Review
Epitaxial Growth of Ga2O3: A Review
by Imteaz Rahaman, Hunter D. Ellis, Cheng Chang, Dinusha Herath Mudiyanselage, Mingfei Xu, Bingcheng Da, Houqiang Fu, Yuji Zhao and Kai Fu
Materials 2024, 17(17), 4261; https://doi.org/10.3390/ma17174261 - 28 Aug 2024
Viewed by 2062
Abstract
Beta-phase gallium oxide (β-Ga2O3) is a cutting-edge ultrawide bandgap (UWBG) semiconductor, featuring a bandgap energy of around 4.8 eV and a highly critical electric field strength of about 8 MV/cm. These properties make it highly suitable for next-generation power [...] Read more.
Beta-phase gallium oxide (β-Ga2O3) is a cutting-edge ultrawide bandgap (UWBG) semiconductor, featuring a bandgap energy of around 4.8 eV and a highly critical electric field strength of about 8 MV/cm. These properties make it highly suitable for next-generation power electronics and deep ultraviolet optoelectronics. Key advantages of β-Ga2O3 include the availability of large-size single-crystal bulk native substrates produced from melt and the precise control of n-type doping during both bulk growth and thin-film epitaxy. A comprehensive understanding of the fundamental growth processes, control parameters, and underlying mechanisms is essential to enable scalable manufacturing of high-performance epitaxial structures. This review highlights recent advancements in the epitaxial growth of β-Ga2O3 through various techniques, including Molecular Beam Epitaxy (MBE), Metal-Organic Chemical Vapor Deposition (MOCVD), Hydride Vapor Phase Epitaxy (HVPE), Mist Chemical Vapor Deposition (Mist CVD), Pulsed Laser Deposition (PLD), and Low-Pressure Chemical Vapor Deposition (LPCVD). This review concentrates on the progress of Ga2O3 growth in achieving high growth rates, low defect densities, excellent crystalline quality, and high carrier mobilities through different approaches. It aims to advance the development of device-grade epitaxial Ga2O3 thin films and serves as a crucial resource for researchers and engineers focused on UWBG semiconductors and the future of power electronics. Full article
(This article belongs to the Section Electronic Materials)
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11 pages, 4251 KiB  
Article
Evaluating Optical Properties of Mixed-Phase 2D MoSe2/Poly(vinyl alcohol) Nanocomposite Film
by Suman Chhetri, Anh Tuan Nguyen, Nicolas Gaillard and Woochul Lee
Materials 2024, 17(17), 4178; https://doi.org/10.3390/ma17174178 - 23 Aug 2024
Viewed by 701
Abstract
Highly solar light-absorbing poly(vinyl alcohol) (PVA) nanocomposite films have garnered wide attention in fields such as flexible optoelectronics, solar energy harvesting, and photothermal therapy. However, fabricating PVA nanocomposite films with a broad spectrum of solar absorption using cost-effective and non-toxic nanofillers remains challenging. [...] Read more.
Highly solar light-absorbing poly(vinyl alcohol) (PVA) nanocomposite films have garnered wide attention in fields such as flexible optoelectronics, solar energy harvesting, and photothermal therapy. However, fabricating PVA nanocomposite films with a broad spectrum of solar absorption using cost-effective and non-toxic nanofillers remains challenging. Herein, nanocomposite films of PVA incorporating various concentrations of mixed-phase 2D MoSe2 nanosheets (i.e., a combination of the 2H and 1T phase) were prepared using a solution casting technique. Scanning electron microscopy (SEM) shows homogenous dispersion of MoSe2 nanosheets in the PVA matrix even at higher concentrations, while atomic force microscopy (AFM) reveals increasing surface roughness with increasing MoSe2 content, reaching a plateau after 20 wt%. With the increase in the concentration of MoSe2, the nanocomposite films exhibit interesting light absorption characteristics reaching their highest absorption (average 94.9%) at 40 wt% MoSe2. The incorporated mixed-phase MoSe2 nanosheets induce a significant change in the energy levels of the PVA matrix, which is reflected in the reduced optical band gap energy (2.63 eV) at 40 wt% MoSe2 against pure PVA (5.28 eV). The excellent light absorption of PVA nanocomposite films across the entire range from 250 nm to 2500 nm is attributed to the thin 2D structure of MoSe2 and the presence of its mixed phase. Full article
(This article belongs to the Special Issue New Insight into Design and Properties of Nanomaterials (Second Edition))
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15 pages, 6460 KiB  
Article
Evaluation of the Properties of 3D-Printed Onyx–Fiberglass Composites
by Jong-Hwan Yun, Gun-Woong Yoon, Yu-Jae Jeon and Min-Soo Kang
Materials 2024, 17(16), 4140; https://doi.org/10.3390/ma17164140 - 21 Aug 2024
Viewed by 1097
Abstract
This study evaluated the properties of 3D-printed Onyx–fiberglass composites. These composites were 3D-printed with zero, one, two, three, and four layers of fiberglass. Ten samples of each configuration were printed for the tensile and flexural tests. The average tensile strength of the Onyx [...] Read more.
This study evaluated the properties of 3D-printed Onyx–fiberglass composites. These composites were 3D-printed with zero, one, two, three, and four layers of fiberglass. Ten samples of each configuration were printed for the tensile and flexural tests. The average tensile strength of the Onyx specimens was calculated to be 44.79 MPa, which increased linearly by approximately 20–25 MPa with each additional fiberglass layer. The elastic moduli calculated from the micromechanics models were compared with the experimental values obtained from the tensile tests. The experimental elastic modulus increased more significantly than the model prediction when more fiberglass layers were added. The flexural modulus of Onyx was 17.6 GPa, which increased with each additional fiberglass layer. This quantitative analysis of composites fabricated using 3D printing highlights their potential for commercialization and industrial applications. Full article
(This article belongs to the Section Advanced Composites)
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24 pages, 13126 KiB  
Article
Forced-Vibration Characteristics of Bowtie-Shaped Honeycomb Composite Sandwich Panel with Viscoelastic Damping Layer
by Siqi Miao, Yifeng Zhong, Mingtao Zhang and Rong Liu
Materials 2024, 17(16), 4067; https://doi.org/10.3390/ma17164067 - 16 Aug 2024
Viewed by 853
Abstract
The incorporation of viscoelastic layers in laminates can markedly enhance the damped dynamic characteristics. This study focuses on integrating viscoelastic layers into the composite facesheet of the bowtie-shaped honeycomb core composite sandwich panel (BHC-CSP). The homogenization of the damped BHC-CSP is performed by [...] Read more.
The incorporation of viscoelastic layers in laminates can markedly enhance the damped dynamic characteristics. This study focuses on integrating viscoelastic layers into the composite facesheet of the bowtie-shaped honeycomb core composite sandwich panel (BHC-CSP). The homogenization of the damped BHC-CSP is performed by employing the variational asymptotic method. Based on the generalized total energy equation, the energy functional of the representative unit cell of the damped BHC-CSP is asymptotically analyzed. The warping function, derived following the principle of minimum potential energy, provides a basis for obtaining the corresponding Euler–Lagrange equation to ascertain the equivalent elastic properties of the damped BHC-CSP. Utilizing the developed two-dimensional equivalent model, the free-vibration characteristics of the damped BHC-CSP are examined across diverse boundary conditions while delving into the impact of an external viscous damping layer on the natural frequency of the damped BHC-CSP. The results reveal that intensified boundary constraints effectively diminish the effective vibration region of the damped BHC-CSP, thereby enhancing its overall stability. The introduction of a PMI foam layer proves effective in adjusting the stiffness and mass distribution of the damped BHC-CSP. Resonance characteristics are explored through frequency and time-domain analyses, highlighting the pivotal roles of the excitation position and receiver point in influencing the displacement and velocity responses. Although the stiffness is improved by incorporating a PMI foam layer, its effect on the damping performance of the damped BHC-CSP is minimal when compared to the T-SW308 foam layer. Full article
(This article belongs to the Section Advanced Composites)
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12 pages, 3470 KiB  
Article
Facilely Promoting the Concentration of Baicalin in Polylactic Acid Fiber for UV Shielding and Antibacterial Functions: A Customized and Sustainable Approach
by Yuyang Zhou, Peng Deng and Wei Chen
Materials 2024, 17(15), 3734; https://doi.org/10.3390/ma17153734 - 28 Jul 2024
Viewed by 821
Abstract
There is a significant trend towards the integration of natural substances with bio-polymers for fully bio-based functional composites. Polylactic acid is regarded as a promising biodegradable polymer for replacing synthetic polymers. Differing from the case of natural fiber, the incompatibility of polylactic acid [...] Read more.
There is a significant trend towards the integration of natural substances with bio-polymers for fully bio-based functional composites. Polylactic acid is regarded as a promising biodegradable polymer for replacing synthetic polymers. Differing from the case of natural fiber, the incompatibility of polylactic acid with bio-based molecules prevents it from being used to fabricate high-quality sustainable composites. This work presents a simultaneous ultraviolet shielding and antibacterial finishing process of polylactic acid combined with bioactive baicalin and an eco-friendly ester, which is highlighted for (a) the lack of synthetic chemicals involved in such process, (b) adsorption enhancement achieved at a mild temperature, and (c) marginal color change on treated polylactic acid. A response surface methodology was adopted to analyze the impacts of various factors on the baicalin quantity in polylactic acid, and to optimize the treatment condition. The uptake ratio of baicalin in polylactic acid was drastically promoted from 8.5 mg/g to 21.1 mg/g using methyl cinnamate. The response surface methodology based on a central composite design experiment indicated that the usage of baicalin was the most significant factor followed by methyl cinnamate and temperature. After optimization, a very faint color depth of 1.2 was apparent, but UPF 50+ and 92% bacterial reduction could be achieved. In all, the success in strengthening of the functionalities of polylactic acid extends the applications of polylactic acid products. Full article
(This article belongs to the Special Issue Advances in the Sustainable Fabrication of Smart and Functional Textiles)
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15 pages, 3035 KiB  
Article
Fiber-Reinforced Equibiaxial Dielectric Elastomer Actuator for Out-of-Plane Displacement
by Simon Holzer, Stefania Konstantinidi, Markus Koenigsdorff, Thomas Martinez, Yoan Civet, Gerald Gerlach and Yves Perriard
Materials 2024, 17(15), 3672; https://doi.org/10.3390/ma17153672 - 25 Jul 2024
Viewed by 946
Abstract
Dielectric elastomer actuators (DEAs) have gained significant attention due to their potential in soft robotics and adaptive structures. However, their performance is often limited by their in-plane strain distribution and limited mechanical stability. We introduce a novel design utilizing fiber reinforcement to address [...] Read more.
Dielectric elastomer actuators (DEAs) have gained significant attention due to their potential in soft robotics and adaptive structures. However, their performance is often limited by their in-plane strain distribution and limited mechanical stability. We introduce a novel design utilizing fiber reinforcement to address these challenges. The fiber reinforcement provides enhanced mechanical integrity and improved strain distribution, enabling efficient energy conversion and out-of-plane displacement. We discuss an analytical model and the fabrication process, including material selection, to realize fiber-reinforced DEAs. Numerical simulations and experimental results demonstrate the performance of the fiber-reinforced equibiaxial DEAs and characterize their displacement and force capabilities. Actuators with four and eight fibers are fabricated with 100 μm and 200 μm dielectric thicknesses. A maximal out-of-plane displacement of 500 μm is reached, with a force of 0.18 N, showing promise for the development of haptic devices. Full article
(This article belongs to the Special Issue Interactive Fiber Rubber Composites—Volume II)
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15 pages, 10388 KiB  
Article
Shear Thickening Fluid and Sponge-Hybrid Triboelectric Nanogenerator for a Motion Sensor Array-Based Lying State Detection System
by Youngsu Kim, Inkyum Kim, Maesoon Im and Daewon Kim
Materials 2024, 17(14), 3536; https://doi.org/10.3390/ma17143536 - 17 Jul 2024
Cited by 2 | Viewed by 1182
Abstract
Issues of size and power consumption in IoT devices can be addressed through triboelectricity-driven energy harvesting technology, which generates electrical signals without external power sources or batteries. This technology significantly reduces the complexity of devices, enhances installation flexibility, and minimizes power consumption. By [...] Read more.
Issues of size and power consumption in IoT devices can be addressed through triboelectricity-driven energy harvesting technology, which generates electrical signals without external power sources or batteries. This technology significantly reduces the complexity of devices, enhances installation flexibility, and minimizes power consumption. By utilizing shear thickening fluid (STF), which exhibits variable viscosity upon external impact, the sensitivity of triboelectric nanogenerator (TENG)-based sensors can be adjusted. For this study, the highest electrical outputs of STF and sponge-hybrid TENG (SSH-TENG) devices under various input forces and frequencies were generated with an open-circuit voltage (VOC) of 98 V and a short-circuit current (ISC) of 4.5 µA. The maximum power density was confirmed to be 0.853 mW/m2 at a load resistance of 30 MΩ. Additionally, a lying state detection system for use in medical settings was implemented using SSH-TENG as a hybrid triboelectric motion sensor (HTMS). Each unit of a 3 × 2 HTMS array, connected to a half-wave rectifier and 1 MΩ parallel resistor, was interfaced with an MCU. Real-time detection of the patient’s condition through the HTMS array could enable the early identification of hazardous situations and alerts. The proposed HTMS continuously monitors the patient’s movements, promptly identifying areas prone to pressure ulcers, thus effectively contributing to pressure ulcer prevention. Full article
(This article belongs to the Special Issue Nanoarchitectonics in Materials Science)
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16 pages, 2959 KiB  
Article
Novel Collagen Membrane Formulations with Irinotecan or Minocycline for Potential Application in Brain Cancer
by Andreea-Anamaria Idu, Mădălina Georgiana Albu Kaya, Ileana Rău, Nicoleta Radu, Cristina-Elena Dinu-Pîrvu and Mihaela Violeta Ghica
Materials 2024, 17(14), 3510; https://doi.org/10.3390/ma17143510 - 15 Jul 2024
Viewed by 1012
Abstract
Our study explores the development of collagen membranes with integrated minocycline or irinotecan, targeting applications in tissue engineering and drug delivery systems. Type I collagen, extracted from bovine skin using advanced fibril-forming technology, was crosslinked with glutaraldehyde to create membranes. These membranes incorporated [...] Read more.
Our study explores the development of collagen membranes with integrated minocycline or irinotecan, targeting applications in tissue engineering and drug delivery systems. Type I collagen, extracted from bovine skin using advanced fibril-forming technology, was crosslinked with glutaraldehyde to create membranes. These membranes incorporated minocycline, an antibiotic, or irinotecan, a chemotherapeutic agent, in various concentrations. The membranes, varying in drug concentration, were studied by water absorption and enzymatic degradation tests, demonstrating a degree of permeability. We emphasize the advantages of local drug delivery for treating high-grade gliomas, highlighting the targeted approach’s efficacy in reducing systemic adverse effects and enhancing drug bioavailability at the tumor site. The utilization of collagen membranes is proposed as a viable method for local drug delivery. Irinotecan’s mechanism, a topoisomerase I inhibitor, and minocycline’s broad antibacterial spectrum and inhibition of glial cell-induced membrane degradation are discussed. We critically examine the challenges posed by the systemic administration of chemotherapeutic agents, mainly due to the blood–brain barrier’s restrictive nature, advocating for local delivery methods as a more effective alternative for glioblastoma treatment. These local delivery strategies, including collagen membranes, are posited as significant advancements in enhancing therapeutic outcomes for glioblastoma patients. Full article
(This article belongs to the Special Issue Novel Green Nanotechnologies Applied in Environmental Protection and Health)
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15 pages, 2643 KiB  
Article
Mechanical and Antimicrobial Properties of the Graphene-Polyamide 6 Composite
by Paweł Głuchowski, Marta Macieja, Robert Tomala, Mariusz Stefanski, Wiesław Stręk, Maciej Ptak, Damian Szymański, Konrad Szustakiewicz, Adam Junka and Bartłomiej Dudek
Materials 2024, 17(14), 3465; https://doi.org/10.3390/ma17143465 - 12 Jul 2024
Cited by 1 | Viewed by 921
Abstract
This paper presents the synthesis and characterization of graphene–polymer composites, focusing on their mechanical and antibacterial properties. Graphene flakes were obtained via an electrochemical method and integrated into polyamide 6 (PA6) matrices using melt intercalation. Various characterization techniques confirmed the quality of the [...] Read more.
This paper presents the synthesis and characterization of graphene–polymer composites, focusing on their mechanical and antibacterial properties. Graphene flakes were obtained via an electrochemical method and integrated into polyamide 6 (PA6) matrices using melt intercalation. Various characterization techniques confirmed the quality of the graphene flakes, including X-ray diffraction (XRD), Raman spectroscopy, and infrared (IR) spectroscopy, as well as scanning and transmission electron microscopy (SEM and TEM) imaging. Mechanical tests showed an increase in the elastic modulus with graphene incorporation, while the impact strength decreased. The SEM analysis highlighted the dispersion of the graphene flakes within the composites and their impact on fracture behavior. Antimicrobial tests demonstrated significant antibacterial properties of the composites, attributed to both oxidative stress and mechanical damage induced by the graphene flakes. The results suggest promising applications for graphene–polymer composites in advanced antimicrobial materials. Full article
(This article belongs to the Special Issue Advances in Polymer Matrix Composites for High Performance Applications)
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20 pages, 5923 KiB  
Article
Engineered Mesoporous Silica-Based Nanoparticles: Characterization of Surface Properties
by Antonio Grisolia, Marzia De Santo, Manuela Curcio, Palmira Alessia Cavallaro, Catia Morelli, Antonella Leggio and Luigi Pasqua
Materials 2024, 17(13), 3352; https://doi.org/10.3390/ma17133352 - 6 Jul 2024
Cited by 2 | Viewed by 1384
Abstract
Mesoporous silica-based nanomaterials have emerged as multifunctional platforms with applications spanning catalysis, medicine, and nanotechnology. Since their synthesis in the early 1990s, these materials have attracted considerable interest due to their unique properties, including high surface area, tunable pore size, and customizable surface [...] Read more.
Mesoporous silica-based nanomaterials have emerged as multifunctional platforms with applications spanning catalysis, medicine, and nanotechnology. Since their synthesis in the early 1990s, these materials have attracted considerable interest due to their unique properties, including high surface area, tunable pore size, and customizable surface chemistry. This article explores the surface properties of a series of MSU-type mesoporous silica nanoparticles, elucidating the impact of different functionalization strategies on surface characteristics. Through an extensive characterization utilizing various techniques, such as FTIR, Z-potential, and nitrogen adsorption porosimetry, insights into the surface modifications of mesoporous silica nanoparticles are provided, contributing to a deeper understanding of their nanostructure and related interactions, and paving the way to possible unexpected actionability and potential applications. Full article
(This article belongs to the Special Issue Physical Synthesis, Properties and Applications of Nanoparticles)
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18 pages, 3698 KiB  
Article
Electronic Properties of Group-III Nitride Semiconductors and Device Structures Probed by THz Optical Hall Effect
by Nerijus Armakavicius, Philipp Kühne, Alexis Papamichail, Hengfang Zhang, Sean Knight, Axel Persson, Vallery Stanishev, Jr-Tai Chen, Plamen Paskov, Mathias Schubert and Vanya Darakchieva
Materials 2024, 17(13), 3343; https://doi.org/10.3390/ma17133343 - 5 Jul 2024
Cited by 1 | Viewed by 1328
Abstract
Group-III nitrides have transformed solid-state lighting and are strategically positioned to revolutionize high-power and high-frequency electronics. To drive this development forward, a deep understanding of fundamental material properties, such as charge carrier behavior, is essential and can also unveil new and unforeseen applications. [...] Read more.
Group-III nitrides have transformed solid-state lighting and are strategically positioned to revolutionize high-power and high-frequency electronics. To drive this development forward, a deep understanding of fundamental material properties, such as charge carrier behavior, is essential and can also unveil new and unforeseen applications. This underscores the necessity for novel characterization tools to study group-III nitride materials and devices. The optical Hall effect (OHE) emerges as a contactless method for exploring the transport and electronic properties of semiconductor materials, simultaneously offering insights into their dielectric function. This non-destructive technique employs spectroscopic ellipsometry at long wavelengths in the presence of a magnetic field and provides quantitative information on the charge carrier density, sign, mobility, and effective mass of individual layers in multilayer structures and bulk materials. In this paper, we explore the use of terahertz (THz) OHE to study the charge carrier properties in group-III nitride heterostructures and bulk material. Examples include graded AlGaN channel high-electron-mobility transistor (HEMT) structures for high-linearity devices, highlighting the different grading profiles and their impact on the two-dimensional electron gas (2DEG) properties. Next, we demonstrate the sensitivity of the THz OHE to distinguish the 2DEG anisotropic mobility parameters in N-polar GaN/AlGaN HEMTs and show that this anisotropy is induced by the step-like surface morphology. Finally, we present the temperature-dependent results on the charge carrier properties of 2DEG and bulk electrons in GaN with a focus on the effective mass parameter and review the effective mass parameters reported in the literature. These studies showcase the capabilities of the THz OHE for advancing the understanding and development of group-III materials and devices. Full article
(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)
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13 pages, 4101 KiB  
Article
Phosphor Ceramic Composite for Tunable Warm White Light
by Ross A. Osborne, Nerine J. Cherepy, Peter S. Bleier, Romain M. Gaume and Stephen A. Payne
Materials 2024, 17(13), 3187; https://doi.org/10.3390/ma17133187 - 29 Jun 2024
Viewed by 844
Abstract
Composite phosphor ceramics for warm white LED lighting were fabricated with K2SiF6:Mn4+ (KSF) as both a narrowband red phosphor and a translucent matrix in which yellow-emitting Y3Al5O12:Ce3+ (YAG) particles were dispersed. [...] Read more.
Composite phosphor ceramics for warm white LED lighting were fabricated with K2SiF6:Mn4+ (KSF) as both a narrowband red phosphor and a translucent matrix in which yellow-emitting Y3Al5O12:Ce3+ (YAG) particles were dispersed. The emission spectra of these composites under blue LED excitation were studied as a function of YAG loading and thickness. Warm white light with a color temperature of 2716 K, a high CRI of 92.6, and an R9 of 77.6 was achieved. A modest improvement in the thermal conductivity of the KSF ceramic of up to 9% was observed with the addition of YAG particles. In addition, a simple model was developed for predicting the emission spectra based on several parameters of the composite ceramics and validated with the experimental results. The emission spectrum can be tuned by varying the dopant concentrations, thickness, YAG loading, and YAG particle size. This work demonstrates the utility of KSF/YAG composite phosphor ceramics as a means of producing warm white light, which are potentially suitable for higher-drive applications due to their increased thermal conductivity and reduced droop compared with silicone-dispersed phosphor powders. Full article
(This article belongs to the Special Issue Study on Rare Earth Doped Luminescent Materials and Transparent Ceramics)
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19 pages, 6679 KiB  
Article
Cu- and Fe-Doped Ni-Mn-Sn Shape Memory Alloys with Enhanced Mechanical and Magnetocaloric Properties
by Siyao Ma, Xuexi Zhang, Guangping Zheng, Mingfang Qian and Lin Geng
Materials 2024, 17(13), 3172; https://doi.org/10.3390/ma17133172 - 28 Jun 2024
Viewed by 861
Abstract
Ni-Mn-Sn-based ferromagnetic shape memory alloys (FSMAs) are multifunctional materials that are promising for solid-state refrigeration applications based on the magnetocaloric effect (MCE) and elastocaloric effect (eCE). However, a combination of excellent multi-caloric properties, suitable operating temperatures, and mechanical properties cannot be well achieved [...] Read more.
Ni-Mn-Sn-based ferromagnetic shape memory alloys (FSMAs) are multifunctional materials that are promising for solid-state refrigeration applications based on the magnetocaloric effect (MCE) and elastocaloric effect (eCE). However, a combination of excellent multi-caloric properties, suitable operating temperatures, and mechanical properties cannot be well achieved in these materials, posing a challenge for their practical application. In this work, we systematically study the phase transformations and magnetic properties of Ni50−xMn38Sn12Cux (x = 0, 2, 3, 4, 5, and 6) and Ni50−yMn38Sn12Fey (y = 0, 1, 2, 3, 4, and 5) alloys, and the magnetic-structural phase diagrams of these alloy systems are reported. The influences of the fourth-element doping on the phase transitions and magnetic properties of the alloys are elucidated by first-principles calculations. This work demonstrates that the fourth-element doping of Ni-Mn-Sn-based FSMA is effective in developing multicaloric refrigerants for practical solid-state refrigeration. Full article
(This article belongs to the Special Issue Physical Metallurgy of Metals and Alloys (3rd Edition))
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21 pages, 4863 KiB  
Article
Antifungal Hybrid Graphene–Transition-Metal Dichalcogenides Aerogels with an Ionic Liquid Additive as Innovative Absorbers for Preventive Conservation of Cultural Heritage
by George Gorgolis, Maria Kotsidi, Elena Messina, Valentina Mazzurco Miritana, Gabriella Di Carlo, Elsa Lesaria Nhuch, Clarissa Martins Leal Schrekker, Jeniffer Alves Cuty, Henri Stephan Schrekker, George Paterakis, Charalampos Androulidakis, Nikos Koutroumanis and Costas Galiotis
Materials 2024, 17(13), 3174; https://doi.org/10.3390/ma17133174 - 28 Jun 2024
Cited by 2 | Viewed by 1239
Abstract
The use and integration of novel materials are increasingly becoming vital tools in the field of preventive conservation of cultural heritage. Chemical factors, such as volatile organic compounds (VOCs), but also environmental factors such as high relative humidity, can lead to degradation, oxidation, [...] Read more.
The use and integration of novel materials are increasingly becoming vital tools in the field of preventive conservation of cultural heritage. Chemical factors, such as volatile organic compounds (VOCs), but also environmental factors such as high relative humidity, can lead to degradation, oxidation, yellowing, and fading of the works of art. To prevent these phenomena, highly porous materials have been developed for the absorption of VOCs and for controlling the relative humidity. In this work, graphene and transition-metal dichalcogenides (TMDs) were combined to create three-dimensional aerogels that absorb certain harmful substances. More specifically, the addition of the TMDs molybdenum disulfide and tungsten disulfide in such macrostructures led to the selective absorption of ammonia. Moreover, the addition of the ionic liquid 1-hexadecyl-3-methylimidazolium chloride promoted higher rates of VOCs absorption and anti-fungal activity against the fungus Aspergillus niger. These two-dimensional materials outperform benchmark porous absorbers in the absorption of all the examined VOCs, such as ammonia, formic acid, acetic acid, formaldehyde, and acetaldehyde. Consequently, they can be used by museums, galleries, or even storage places for the perpetual protection of works of art. Full article
(This article belongs to the Special Issue Materials in Cultural Heritage: Analysis, Testing, and Preservation)
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91 pages, 19320 KiB  
Review
Ammonothermal Crystal Growth of Functional Nitrides for Semiconductor Devices: Status and Potential
by Thomas Wostatek, V. Y. M. Rajesh Chirala, Nathan Stoddard, Ege N. Civas, Siddha Pimputkar and Saskia Schimmel
Materials 2024, 17(13), 3104; https://doi.org/10.3390/ma17133104 - 25 Jun 2024
Viewed by 1791
Abstract
The state-of-the-art ammonothermal method for the growth of nitrides is reviewed here, with an emphasis on binary and ternary nitrides beyond GaN. A wide range of relevant aspects are covered, from fundamental autoclave technology, to reactivity and solubility of elements, to synthesized crystalline [...] Read more.
The state-of-the-art ammonothermal method for the growth of nitrides is reviewed here, with an emphasis on binary and ternary nitrides beyond GaN. A wide range of relevant aspects are covered, from fundamental autoclave technology, to reactivity and solubility of elements, to synthesized crystalline nitride materials and their properties. Initially, the potential of emerging and novel nitrides is discussed, motivating their synthesis in single crystal form. This is followed by a summary of our current understanding of the reactivity/solubility of species and the state-of-the-art single crystal synthesis for GaN, AlN, AlGaN, BN, InN, and, more generally, ternary and higher order nitrides. Investigation of the synthesized materials is presented, with a focus on point defects (impurities, native defects including hydrogenated vacancies) based on GaN and potential pathways for their mitigation or circumvention for achieving a wide range of controllable functional and structural material properties. Lastly, recent developments in autoclave technology are reviewed, based on GaN, with a focus on advances in development of in situ technologies, including in situ temperature measurements, optical absorption via UV/Vis spectroscopy, imaging of the solution and crystals via optical (visible, X-ray), along with use of X-ray computed tomography and diffraction. While time intensive to develop, these technologies are now capable of offering unprecedented insight into the autoclave and, hence, facilitating the rapid exploration of novel nitride synthesis using the ammonothermal method. Full article
(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)
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27 pages, 17029 KiB  
Article
Influence of the Addition of TiO2 Nanoparticles on the Self-Cleaning Capacity of Cementitious Composites
by Carmen Teodora Florean, Alexandra Csapai, Horatiu Vermesan, Timea Gabor, Andreea Hegyi, Vlad Stoian, Willi Andrei Uriciuc, Cristian Petcu and Marius Cîmpan
Materials 2024, 17(13), 3098; https://doi.org/10.3390/ma17133098 - 25 Jun 2024
Viewed by 3917
Abstract
This study evaluated the potential of incorporating TiO2 nanoparticles (NT) into cementitious composites to provide self-cleaning and self-sanitising properties, as well as the partial replacement of natural aggregates with recycled glass (RGA), ceramic brick (RBA), granulated blast furnace slag (GBA), and textolite [...] Read more.
This study evaluated the potential of incorporating TiO2 nanoparticles (NT) into cementitious composites to provide self-cleaning and self-sanitising properties, as well as the partial replacement of natural aggregates with recycled glass (RGA), ceramic brick (RBA), granulated blast furnace slag (GBA), and textolite waste (RTA) from electronic equipment on these properties. Based on the research results, the addition of NT to cementitious composites led to a significant reduction in contact angle, which means an increase in surface hydrophilicity. At the same time, Rhodamine B stain fading was highlighted, with the degree of whiteness recovery of NT composites exceeding that of the control by up to 11% for natural aggregate compositions, 10.6% for RGA compositions, 19.9% for RBA compositions, 15% for GBA compositions, and 13% for RTA compositions. In a mould-contaminated environment, it was shown that the introduction of NT allowed the material to develop a biocidal surface capacity which is also influenced by the nature of the aggregates used. Furthermore, the study revealed that, under controlled conditions, certain recycled waste aggregates, such as textolite, promoted mould growth, while others, such as brick and slag, inhibited it, highlighting not just the effect of the addition of NT, but also the significant influence of the aggregate type on the microbial resistance of cementitious composites. These improvements in the performance of cementitious composites are particularly advantageous when applied to prefabricated elements intended for the finishing and decorative surfaces of institutional (schools, administrative buildings, religious structures, etc.) or residential buildings. Full article
(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))
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11 pages, 10922 KiB  
Article
Model of Shape Memory Alloy Actuator with the Usage of LSTM Neural Network
by Waldemar Rączka and Marek Sibielak
Materials 2024, 17(13), 3114; https://doi.org/10.3390/ma17133114 - 25 Jun 2024
Cited by 1 | Viewed by 1069
Abstract
Shape Memory Alloys (SMAs) are used to design actuators, which are one of the most fascinating applications of SMA. Usually, they are on-off actuators because, in the case of continuous actuators, the nonlinearity of their characteristics is the problem. The main problem, especially [...] Read more.
Shape Memory Alloys (SMAs) are used to design actuators, which are one of the most fascinating applications of SMA. Usually, they are on-off actuators because, in the case of continuous actuators, the nonlinearity of their characteristics is the problem. The main problem, especially in control systems in these actuators, is a hysteretic loop. There are many models of hysteresis, but from a control theory point of view, they are not helpful. This study used an artificial neural network (ANN) to model the SMA actuator hysteresis. The ANN structure and training method are presented in the paper. Data were generated from the Preisach model for training. This approach allowed for quick and controllable data generation, making experiments thoroughly planned and repeatable. The advantage and disadvantage of this approach is the lack of disturbances. The paper’s main goal is to model an SMA actuator. Additionally, it explores whether and how an ANN can describe and model the hysteresis loop. A literature review shows that ANNs are used to model hysteresis, but to a limited extent; this means that the hysteresis loop was modelled with a hysteretic element. Full article
(This article belongs to the Special Issue Modeling and Design Based on Shape Memory Behavior)
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9 pages, 2034 KiB  
Article
Anisotropic Optical Response of Ti-Doped VO2 Single Crystals
by Salvatore Macis, Lorenzo Mosesso, Annalisa D’Arco, Andrea Perucchi, Paola Di Pietro and Stefano Lupi
Materials 2024, 17(13), 3121; https://doi.org/10.3390/ma17133121 - 25 Jun 2024
Cited by 1 | Viewed by 1014
Abstract
This study delves into the effects of titanium (Ti) doping on the optical properties of vanadium dioxide (VO2), a material well known for its metal–to–insulator transition (MIT) near room temperature. By incorporating Ti into VO2’s crystal lattice, we aim [...] Read more.
This study delves into the effects of titanium (Ti) doping on the optical properties of vanadium dioxide (VO2), a material well known for its metal–to–insulator transition (MIT) near room temperature. By incorporating Ti into VO2’s crystal lattice, we aim to uncover the resultant changes in its physical properties, crucial for enhancing its application in smart devices. Utilizing polarized infrared micro–spectroscopy, we examined TixV1−xO2 single crystals with varying Ti concentrations (x = 0.059, x = 0.082, and x = 0.187) across different crystal phases (the conductive rutile phase and insulating monoclinic phases M1 and M2) from the far–infrared to the visible spectral range. Our findings reveal that Ti doping significantly influences the phononic spectra, introducing absorption peaks not attributed to pure VO2 or TiO2. This is especially notable with polarization along the crystal growth axis, mainly in the x = 0.187 sample. Furthermore, we demonstrate that the electronic contribution to optical conductivity in the metallic phase exhibits strong anisotropy, higher along the c axis than the a–b plane. This anisotropy, coupled with the progressive broadening of the zone center infrared active phonon modes with increasing doping, highlights the complex interplay between structural and electronic dynamics in doped VO2. Our results underscore the potential of Ti doping in fine-tuning VO2’s electronic and thermochromic properties, paving the way for its enhanced application in optoelectronic devices and technologies. Full article
(This article belongs to the Section Advanced Materials Characterization)
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24 pages, 11093 KiB  
Article
Experimental Study on the Flexural Performance of Steel–Polyvinyl Alcohol Hybrid Fiber-Reinforced Concrete
by Jingjiang Wu, Wenjie Zhang, Juhong Han, Zheyuan Liu, Jie Liu and Yafei Huang
Materials 2024, 17(13), 3099; https://doi.org/10.3390/ma17133099 - 25 Jun 2024
Viewed by 768
Abstract
This paper explores the impact of steel–PVA hybrid fibers (S-PVA HF) on the flexural performance of panel concrete via three-point bending tests. Crack development in the concrete is analyzed through Digital Image Correlation (DIC) and Scanning Electron Microscope (SEM) experiments, unveiling the underlying [...] Read more.
This paper explores the impact of steel–PVA hybrid fibers (S-PVA HF) on the flexural performance of panel concrete via three-point bending tests. Crack development in the concrete is analyzed through Digital Image Correlation (DIC) and Scanning Electron Microscope (SEM) experiments, unveiling the underlying mechanisms. The evolution of cracks in concrete is quantitatively analyzed based on fractal theory, and a predictive model for flexural strength (PMFS) is established. The results show that the S-PVA HF exhibits a synergistic effect in enhancing and toughening the concrete at multi-scale. The crack area of steel–PVA hybrid fiber concrete (S-PVA HFRC) is linearly correlated with deflection (δ), and it further reduces the crack development rate and crack area compared to steel fiber-reinforced concrete (SFRC). The S-PVA HF improves the proportional ultimate strength (fL) and residual flexural strength (fR,j) of concrete, and the optimal flexural performance of concrete is achieved when the steel fiber dosage is 1.0% and the PVA fiber dosage is 0.2%. The established PMFS of hybrid fiber-reinforced concrete (HFRC) can effectively predict the flexural strength of concrete. Full article
(This article belongs to the Special Issue Numerical Modeling and Mechanical Properties of Fiber-Reinforced Cementitious Composites)
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20 pages, 4483 KiB  
Article
Modern Rare Earth Imprinted Membranes for the Recovery of Rare Earth Metal Ions from Coal Fly Ash Extracts
by Aleksandra Rybak, Aurelia Rybak, Sławomir Boncel, Anna Kolanowska, Agata Jakóbik-Kolon, Joanna Bok-Badura and Waldemar Kaszuwara
Materials 2024, 17(13), 3087; https://doi.org/10.3390/ma17133087 - 24 Jun 2024
Cited by 1 | Viewed by 1228
Abstract
The need to identify secondary sources of REEs and their recovery has led to the search for new methods and materials. In this study, a novel type of ion-imprinted adsorption membranes based on modified chitosan was synthesized. Their application for the recovery of [...] Read more.
The need to identify secondary sources of REEs and their recovery has led to the search for new methods and materials. In this study, a novel type of ion-imprinted adsorption membranes based on modified chitosan was synthesized. Their application for the recovery of chosen REEs from synthetic coal fly ash extracts was analyzed. The examined membranes were analyzed in terms of adsorption kinetics, isotherms, selectivity, reuse, and their separation abilities. The experimental data obtained were analyzed with two applications, namely, REE 2.0 and REE_isotherm. It was found that the adsorption of Nd3+ and Y3+ ions in the obtained membranes took place according to the chemisorption mechanism and was significantly controlled by film diffusion. The binding sites on the adsorbent surface were uniformly distributed; the examined ions showed the features of regular monolayer adsorption; and the adsorbents showed a strong affinity to the REE ions. The high values of Kd (900–1472.8 mL/g) demonstrate their high efficiency in the recovery of REEs. After five subsequent adsorption–desorption processes, approximately 85% of the value of one cycle was reached. The synthesized membranes showed a high rejection of the matrix components (Na, Mg, Ca, Al, Fe, and Si) in the extracts of the coal fly ashes, and the retention ratio for these Nd and Y ions was 90.11% and 80.95%, respectively. Full article
(This article belongs to the Special Issue Current and Future Trends in Mineral Processing and Extractive Metallurgy)
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16 pages, 1564 KiB  
Review
Piezoelectric Charge Coefficient of Halide Perovskites
by Raja Sekhar Muddam, Joseph Sinclair and Lethy Krishnan Jagadamma
Materials 2024, 17(13), 3083; https://doi.org/10.3390/ma17133083 - 23 Jun 2024
Viewed by 1181
Abstract
Halide perovskites are an emerging family of piezoelectric and ferroelectric materials. These materials can exist in bulk, single-crystal, and thin-film forms. In this article, we review the piezoelectric charge coefficient (dij) of single crystals, thin films, and dimension-tuned halide perovskites based [...] Read more.
Halide perovskites are an emerging family of piezoelectric and ferroelectric materials. These materials can exist in bulk, single-crystal, and thin-film forms. In this article, we review the piezoelectric charge coefficient (dij) of single crystals, thin films, and dimension-tuned halide perovskites based on different measurement methods. Our study finds that the (dij) coefficient of the bulk and single-crystal samples is mainly measured using the quasi-static (Berlincourt) method, though the piezoforce microscopy (PFM) method is also heavily used. In the case of thin-film samples, the (dij) coefficient is dominantly measured by the PFM technique. The reported values of dij coefficients of halide perovskites are comparable and even better in some cases compared to existing materials such as PZT and PVDF. Finally, we discuss the promising emergence of quasi-static methods for thin-film samples as well. Full article
(This article belongs to the Special Issue Piezoelectrics and Ferroelectrics for End Users)
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21 pages, 3610 KiB  
Article
Examination of Beam Theories for Buckling and Free Vibration of Functionally Graded Porous Beams
by Shuaishuai Wu, Yilin Li, Yumei Bao, Jun Zhu and Helong Wu
Materials 2024, 17(13), 3080; https://doi.org/10.3390/ma17133080 - 22 Jun 2024
Cited by 3 | Viewed by 1251
Abstract
This paper examines the accuracy and effectiveness of various beam theories in predicting the critical buckling loads and fundamental frequencies of functionally graded porous (FGP) beams whose material properties change continuously across the thickness. The beam theories considered are classical beam theory (CBT), [...] Read more.
This paper examines the accuracy and effectiveness of various beam theories in predicting the critical buckling loads and fundamental frequencies of functionally graded porous (FGP) beams whose material properties change continuously across the thickness. The beam theories considered are classical beam theory (CBT), first-order shear deformation beam theory (FSDBT), third-order shear deformation beam theory (TSDBT), and the broken-line hypothesis-based shear deformation beam theory (BSDBT). Governing equations for those beam theories are formulated by using the Hamilton’s principle and are then solved by means of the generalised differential quadrature method. Finite element simulation solutions are provided as reference results to assess the predictions of those beam theories. Comprehensive numerical results are presented to evaluate the influences of the porosity distribution and coefficient, slenderness ratio, and boundary condition on the difference between theoretical predictions and simulation results. It is found that the differences significantly increase as the porosity coefficient rises, and this effect becomes more noticeable for the rigid beam with a smaller slenderness ratio. Nonetheless, the results produced by the BSDBT are always the closest to simulation ones. The findings in this paper will contribute to the establishment of more refined theories for the mechanical analysis of FGP structures. Full article
(This article belongs to the Section Porous Materials)
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21 pages, 4887 KiB  
Review
Recent Progress in Creep-Resistant Aluminum Alloys for Diesel Engine Applications: A Review
by Raul Irving Arriaga-Benitez and Mihriban Pekguleryuz
Materials 2024, 17(13), 3076; https://doi.org/10.3390/ma17133076 - 22 Jun 2024
Cited by 3 | Viewed by 1063
Abstract
Diesel engines in heavy-duty vehicles are predicted to maintain a stable presence in the future due to the difficulty of electrifying heavy trucks, mine equipment, and railway cars. This trend encourages the effort to develop new aluminum alloy systems with improved performance at [...] Read more.
Diesel engines in heavy-duty vehicles are predicted to maintain a stable presence in the future due to the difficulty of electrifying heavy trucks, mine equipment, and railway cars. This trend encourages the effort to develop new aluminum alloy systems with improved performance at diesel engine conditions of elevated temperature and stress combinations to reduce vehicle weight and, consequently, CO2 emissions. Aluminum alloys need to provide adequate creep resistance at ~300 °C and room-temperature tensile properties better than the current commercial aluminum alloys used for powertrain applications. The studies for improving creep resistance for aluminum casting alloys indicate that their high-temperature stability depends on the formation of high-density uniform dispersoids with low solid solubility and low diffusivity in aluminum. This review summarizes three generations of diesel engine aluminum alloys and focuses on recent work on the third-generation dispersoid-strengthened alloys. Additionally, new trends in developing creep resistance through the development of alloy systems other than Al-Si-based alloys, the optimization of manufacturing processes, and the use of thermal barrier coatings and composites are discussed. New progress on concepts regarding the thermal stability of rapidly solidified and nano-structured alloys and on creep-resistant alloy design via machine learning-based algorithms is also presented. Full article
(This article belongs to the Special Issue Development of Advanced Aluminum and Magnesium Alloys: Microstructure, Mechanical Properties and Processing)
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27 pages, 17974 KiB  
Review
Properties and Applications of Iron–Chalcogenide Superconductors
by Jianlong Zhao, Junsong Liao, Chiheng Dong, Dongliang Wang and Yanwei Ma
Materials 2024, 17(13), 3059; https://doi.org/10.3390/ma17133059 - 21 Jun 2024
Viewed by 908
Abstract
Iron–chalcogenide superconductors continue to captivate researchers due to their diverse crystalline structures and intriguing superconducting properties, positioning them as both a valuable platform for theoretical investigations and promising candidates for practical applications. This review begins with a comprehensive overview of the fabrication techniques [...] Read more.
Iron–chalcogenide superconductors continue to captivate researchers due to their diverse crystalline structures and intriguing superconducting properties, positioning them as both a valuable platform for theoretical investigations and promising candidates for practical applications. This review begins with a comprehensive overview of the fabrication techniques employed for various iron–chalcogenide superconductors, accompanied by a summary of their phase diagrams. Subsequently, it delves into the upper critical field, anisotropy, and critical current density. Furthermore, it discusses the successful fabrication of meters-long coated conductors and explores their applications in superconducting radio-frequency cavities and coils. Finally, several prospective avenues for future research are proposed. Full article
(This article belongs to the Special Issue Advances in Cuprates and Iron-Based Superconductors: Physics, Properties, and Applications)
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13 pages, 2343 KiB  
Article
Thermodynamic Model for Hydrogen Production from Rice Straw Supercritical Water Gasification
by Zhigang Liu, Zhiyong Peng, Lei Yi, Le Wang, Jingwei Chen, Bin Chen and Liejin Guo
Materials 2024, 17(12), 3038; https://doi.org/10.3390/ma17123038 - 20 Jun 2024
Viewed by 1014
Abstract
Supercritical water gasification (SCWG) technology is highly promising for its ability to cleanly and efficiently convert biomass to hydrogen. This paper developed a model for the gasification of rice straw in supercritical water (SCW) to predict the direction and limit of the reaction [...] Read more.
Supercritical water gasification (SCWG) technology is highly promising for its ability to cleanly and efficiently convert biomass to hydrogen. This paper developed a model for the gasification of rice straw in supercritical water (SCW) to predict the direction and limit of the reaction based on the Gibbs free energy minimization principle. The equilibrium distribution of rice straw gasification products was analyzed under a wide range of parameters including temperatures of 400–1200 °C, pressures of 20–50 MPa, and rice straw concentrations of 5–40 wt%. Coke may not be produced due to the excellent properties of supercritical water under thermodynamic constraints. Higher temperatures, lower pressures, and biomass concentrations facilitated the movement of the chemical equilibrium towards hydrogen production. The hydrogen yield was 47.17 mol/kg at a temperature of 650 °C, a pressure of 25 MPa, and a rice straw concentration of 5 wt%. Meanwhile, there is an absorptive process in the rice straw SCWG process for high-calorific value hydrogen production. Energy self-sufficiency of the SCWG process can be maintained by adding small amounts of oxygen (ER < 0.2). This work would be of great value in guiding rice straw SCWG experiments. Full article
(This article belongs to the Special Issue Application of Biomass Materials in the Fields of Electrochemistry and Thermochemistry)
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18 pages, 5495 KiB  
Article
Accelerated Design for Perovskite-Oxide-Based Photocatalysts Using Machine Learning Techniques
by Xiuyun Zhai and Mingtong Chen
Materials 2024, 17(12), 3026; https://doi.org/10.3390/ma17123026 - 20 Jun 2024
Viewed by 951
Abstract
The rapid discovery of photocatalysts with desired performance among tens of thousands of potential perovskites represents a significant advancement. To expedite the design of perovskite-oxide-based photocatalysts, we developed a model of ABO3-type perovskites using machine learning methods based on atomic and [...] Read more.
The rapid discovery of photocatalysts with desired performance among tens of thousands of potential perovskites represents a significant advancement. To expedite the design of perovskite-oxide-based photocatalysts, we developed a model of ABO3-type perovskites using machine learning methods based on atomic and experimental parameters. This model can be used to predict specific surface area (SSA), a key parameter closely associated with photocatalytic activity. The model construction involved several steps, including data collection, feature selection, model construction, web-service development, virtual screening and mechanism elucidation. Statistical analysis revealed that the support vector regression model achieved a correlation coefficient of 0.9462 for the training set and 0.8786 for the leave-one-out cross-validation. The potential perovskites with higher SSA than the highest SSA observed in the existing dataset were identified using the model and our computation platform. We also developed a webserver of the model, freely accessible to users. The methodologies outlined in this study not only facilitate the discovery of new perovskites but also enable exploration of the correlations between the perovskite properties and the physicochemical features. These findings provide valuable insights for further research and applications of perovskites using machine learning techniques. Full article
(This article belongs to the Section Materials Simulation and Design)
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16 pages, 2744 KiB  
Article
Thermal Stability of Encapsulated Carbon-Based Multiporous-Layered-Electrode Perovskite Solar Cells Extended to Over 5000 h at 85 °C
by Ryuki Tsuji, Yuuma Nagano, Kota Oishi, Eiji Kobayashi and Seigo Ito
Materials 2024, 17(12), 3002; https://doi.org/10.3390/ma17123002 - 19 Jun 2024
Cited by 4 | Viewed by 1353
Abstract
The key to the practical application of organometal–halide crystals perovskite solar cells (PSCs) is to achieve thermal stability through robust encapsulation. This paper presents a method to significantly extend the thermal stability lifetime of perovskite solar cells to over 5000 h at 85 [...] Read more.
The key to the practical application of organometal–halide crystals perovskite solar cells (PSCs) is to achieve thermal stability through robust encapsulation. This paper presents a method to significantly extend the thermal stability lifetime of perovskite solar cells to over 5000 h at 85 °C by demonstrating an optimal combination of encapsulation methods and perovskite composition for carbon-based multiporous-layered-electrode (MPLE)-PSCs. We fabricated four types of MPLE-PSCs using two encapsulation structures (over- and side-sealing with thermoplastic resin films) and two perovskite compositions ((5-AVA)x(methylammonium (MA))1−xPbI3 and (formamidinium (FA))0.9Cs0.1PbI3), and analyzed the 85 °C thermal stability followed by the ISOS-D-2 protocol. Without encapsulation, FA0.9Cs0.1PbI3 exhibited higher thermal stability than (5-AVA)x(MA)1−xPbI3. However, encapsulation reversed the phenomenon (that of (5-AVA)x(MA)1−xPbI3 became stronger). The combination of the (5-AVA)x(MA)1−xPbI3 perovskite absorber and over-sealing encapsulation effectively suppressed the thermal degradation, resulting in a PCE value of 91.2% of the initial value after 5072 h. On the other hand, another combination (side-sealing on (5-AVA)x(MA)1−xPbI3 and over- and side-sealing on FA0.9Cs0.1PbI3) resulted in decreased stability. The FACs-based perovskite was decomposed from these degradation mechanisms by the condensation reaction between FA and carbon. For side-sealing, the space between the cell and the encapsulant was estimated to contain approximately 1,260,000 times more H2O than in over-sealing, which catalyzed the degradation of the perovskite crystals. Our results demonstrate that MA-based PSCs, which are generally considered to be thermally sensitive, can significantly extend their thermal stability after proper encapsulation. Therefore, we emphasize that finding the appropriate combination of encapsulation technique and perovskite composition is quite important to achieve further device stability. Full article
(This article belongs to the Special Issue Advanced Perovskite Solar Cells: Compatible Materials and Processes)
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21 pages, 10012 KiB  
Article
Numerical Simulation of Friction Stir Welding of Dissimilar Al/Mg Alloys Using Coupled Level Set and Volume of Fluid Method
by Guanlan Zhang, Jinqiang Gao and Chuansong Wu
Materials 2024, 17(12), 3014; https://doi.org/10.3390/ma17123014 - 19 Jun 2024
Cited by 1 | Viewed by 686
Abstract
The coupled level set and volume of fluid (CLSVOF) method is proposed to simulate the material distribution and physical properties during dissimilar aluminum/magnesium friction stir welding (FSW) process more accurately. Combined with a computational fluid dynamics model, the FSW process is numerically simulated [...] Read more.
The coupled level set and volume of fluid (CLSVOF) method is proposed to simulate the material distribution and physical properties during dissimilar aluminum/magnesium friction stir welding (FSW) process more accurately. Combined with a computational fluid dynamics model, the FSW process is numerically simulated and the heat transfer and material flow are analyzed. The results show that heat transfer and material flow have great influence on the Al/Mg bonding. In order to verify the accuracy of the model, the calculated results based on different methods are compared with the experimental results, and the Al/Mg interface simulated by the CLSVOF method is in better agreement with the experimental results. Finally, the material distribution and interface evolution near the tool at different times were studied based on the CLSVOF method. Full article
(This article belongs to the Section Metals and Alloys)
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41 pages, 24667 KiB  
Review
Titanium Alloy Materials with Very High Cycle Fatigue: A Review
by Yuhang Wu, Weifeng He, Haitao Ma, Xiangfan Nie, Xiaoqing Liang, Jile Pan, Shiguang Wang, Min Shang and Li Cheng
Materials 2024, 17(12), 2987; https://doi.org/10.3390/ma17122987 - 18 Jun 2024
Cited by 1 | Viewed by 1275
Abstract
As the reliability and lifespan requirements of modern equipment continues to escalate, the problems with very high cycle fatigue (VHCF) has obtained increasingly widespread attention, becoming a hot topic in fatigue research. Titanium alloys, which are the most extensively used metal materials in [...] Read more.
As the reliability and lifespan requirements of modern equipment continues to escalate, the problems with very high cycle fatigue (VHCF) has obtained increasingly widespread attention, becoming a hot topic in fatigue research. Titanium alloys, which are the most extensively used metal materials in the modern aerospace industry, are particularly prone to VHCF issues. The present study systematically reviewed and summarized the latest (since 2010) developments in VHCF research on titanium alloy, with special focus on the (i) experimental methods, (ii) macroscopic and microscopic characteristics of the fatigue fractures, and (iii) construction of fatigue fracture models. More specifically, the review addresses the technological approaches that were used, mechanisms of fatigue crack initiation, features of the S–N curves and Goodman diagrams, and impact of various factors (such as processing, temperature, and corrosion). In addition, it elucidates the damage mechanisms, evolution, and modeling of VHCF in titanium alloys, thereby improving the understanding of VHCF patterns in titanium alloys and highlighting the current challenges in VHCF research. Full article
(This article belongs to the Special Issue Mechanics Behavior, Fatigue Damage, and Microstructure Evolution of Metallic Material)
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13 pages, 2619 KiB  
Article
High-Strain-Rate Deformation Behavior of Co0.96Cr0.76Fe0.85Ni1.01Hf0.40 Eutectic High-Entropy Alloy at Room and Cryogenic Temperatures
by Kun Jiang, Zhiping Xiong and Xi Chen
Materials 2024, 17(12), 2995; https://doi.org/10.3390/ma17122995 - 18 Jun 2024
Cited by 2 | Viewed by 1061
Abstract
The deformation behaviors of Co0.96Cr0.76Fe0.85Ni1.01Hf0.40 eutectic high-entropy alloy (EHEA) under high strain rates have been investigated at both room temperature (RT, 298 K) and liquid nitrogen temperature (LNT, 77 K). The current Co0.96 [...] Read more.
The deformation behaviors of Co0.96Cr0.76Fe0.85Ni1.01Hf0.40 eutectic high-entropy alloy (EHEA) under high strain rates have been investigated at both room temperature (RT, 298 K) and liquid nitrogen temperature (LNT, 77 K). The current Co0.96Cr0.76Fe0.85Ni1.01Hf0.40 EHEA exhibits a high yield strength of 740 MPa along with a high fracture strain of 35% under quasi-static loading. A remarkable positive strain rate effect can be observed, and its yield strength increased to 1060 MPa when the strain rate increased to 3000/s. Decreasing temperature will further enhance the yield strength significantly. The yield strength of this alloy at a strain rate of 3000/s increases to 1240 MPa under the LNT condition. Moreover, the current EHEA exhibits a notable increased strain-hardening ability with either an increasing strain rate or a decreasing temperature. Transmission electron microscopy (TEM) characterization uncovered that the dynamic plastic deformation of this EHEA at RT is dominated by dislocation slip. However, under severe conditions of high strain rate in conjunction with LNT, dislocation dissociation is promoted, resulting in a higher density of nanoscale deformation twins, stacking faults (SFs) as well as immobile Lomer–Cottrell (L-C) dislocation locks. These deformation twins, SFs and immobile dislocation locks function effectively as dislocation barriers, contributing notably to the elevated strain-hardening rate observed during dynamic deformation at LNT. Full article
(This article belongs to the Section Advanced Materials Characterization)
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28 pages, 4517 KiB  
Article
Mobility of Zn and Cu in Bentonites: Implications for Environmental Remediation
by Edyta Nartowska, Anna Podlasek, Magdalena Daria Vaverková, Eugeniusz Koda, Aleksandra Jakimiuk, Robert Kowalik and Tomasz Kozłowski
Materials 2024, 17(12), 2957; https://doi.org/10.3390/ma17122957 - 17 Jun 2024
Cited by 2 | Viewed by 1162
Abstract
The aim of this study was to evaluate the mobility of copper (Cu) and zinc (Zn) and their impact on the properties of bentonites and unfrozen water content. Limited research in this area necessitates further analysis to prevent the negative effects of metal [...] Read more.
The aim of this study was to evaluate the mobility of copper (Cu) and zinc (Zn) and their impact on the properties of bentonites and unfrozen water content. Limited research in this area necessitates further analysis to prevent the negative effects of metal interactions on bentonite effectiveness. Tests involved American (SWy-3, Stx-1b) and Slovak (BSvk) bentonite samples with Zn or Cu ion exchange. Sequential extraction was performed using the Community Bureau of Reference (BCR) method. Elemental content was analyzed via inductively coupled plasma optical emission spectrometry (ICP-OES). Unfrozen water content was measured using nuclear magnetic resonance (1H-NMR) and differential scanning calorimetry (DSC). Results showed a significant influence of the main cation (Zn or Cu) on ion mobility, with toxic metal concentrations increasing mobility and decreasing residual fractions. Mobile Zn fractions increased with larger particle diameters, lower clay content, and shorter interplanar spacing, while the opposite was observed for Cu. Zn likely accumulated in larger clay pores, while Cu was immobilized in the bentonite complex. The stability of Zn or Cu ions increased with higher clay content or specific surface area. Residual Zn or Cu fractions were highest in uncontaminated bentonites with higher unfrozen water content, suggesting the potential formation of concentrated solutions in sub-zero temperatures, posing a threat to the clay–water environment, especially in cold regions. Full article
(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))
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16 pages, 22531 KiB  
Article
Aggregation–Growth and Densification Behavior of Titanium Particles in Molten Mg-MgCl2 System
by Xin Yang, Kaihua Li, Jun Li, Zhuo Sheng and Ying Liu
Materials 2024, 17(12), 2904; https://doi.org/10.3390/ma17122904 - 13 Jun 2024
Viewed by 772
Abstract
In this work, the preparation of titanium sponge by magnesium thermal method is regarded as the liquid-phase sintering process of titanium, and powder-metallurgy sintering technology is utilized to simulate the aggregation–growth and densification behavior of titanium particles in a high-temperature liquid medium (the [...] Read more.
In this work, the preparation of titanium sponge by magnesium thermal method is regarded as the liquid-phase sintering process of titanium, and powder-metallurgy sintering technology is utilized to simulate the aggregation–growth and densification behavior of titanium particles in a high-temperature liquid medium (the molten Mg-MgCl2 system). It was found that compared with MgCl2, Mg has better high-temperature wettability and reduction effect, which promotes titanium particles to form a sponge titanium skeleton at lower temperature. The aggregation degree of titanium particles and the densification degree of a sponge titanium skeleton can be improved by increasing the temperature and the relative content of Mg in the melting medium. The kinetics study shows that with the increase in temperature, the porosity of the titanium particle aggregates and the sponge titanium skeleton decreases, and their density growth rate increases. With the extension of time, the aggregation degree of titanium particles and the densification degree of sponge titanium gradually increase. This work provides a theoretical reference for controlling the density of titanium sponge in industry. Full article
(This article belongs to the Special Issue Porous Metals: Preparation, Microstructure, Properties and Performance)
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14 pages, 2127 KiB  
Article
The Effect of Cesium Incorporation on the Vibrational and Elastic Properties of Methylammonium Lead Chloride Perovskite Single Crystals
by Syed Bilal Junaid, Furqanul Hassan Naqvi and Jae-Hyeon Ko
Materials 2024, 17(12), 2862; https://doi.org/10.3390/ma17122862 - 12 Jun 2024
Viewed by 786
Abstract
Hybrid organic-inorganic lead halide perovskites (LHPs) have emerged as a highly significant class of materials due to their tunable and adaptable properties, which make them suitable for a wide range of applications. One of the strategies for tuning and optimizing LHP-based devices is [...] Read more.
Hybrid organic-inorganic lead halide perovskites (LHPs) have emerged as a highly significant class of materials due to their tunable and adaptable properties, which make them suitable for a wide range of applications. One of the strategies for tuning and optimizing LHP-based devices is the substitution of cations and/or anions in LHPs. The impact of Cs substitution at the A site on the structural, vibrational, and elastic properties of MAxCs1−xPbCl3-mixed single crystals was investigated using X-ray diffraction (XRD) and Raman and Brillouin light scattering techniques. The XRD results confirmed the successful synthesis of impurity-free single crystals, which exhibited a phase coexistence of dominant cubic and minor orthorhombic symmetries. Raman spectroscopy was used to analyze the vibrational modes associated with the PbCl6 octahedra and the A-site cation movements, thereby revealing the influence of cesium incorporation on the lattice dynamics. Brillouin spectroscopy was employed to investigate the changes in elastic properties resulting from the Cs substitution. The incorporation of Cs cations induced lattice distortions within the inorganic framework, disrupting the hydrogen bonding between the MA cations and PbCl6 octahedra, which in turn affected the elastic constants and the sound velocities. The substitution of the MA cations with smaller Cs cations resulted in a stiffer lattice structure, with the two elastic constants increasing up to a Cs content of 30%. The current findings facilitate a fundamental understanding of mixed lead chloride perovskite materials, providing valuable insights into their structural and vibrational properties. Full article
(This article belongs to the Special Issue Terahertz Vibrational Spectroscopy in Advanced Materials)
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14 pages, 5499 KiB  
Article
Comparison of Magnetron-Sputtered and Cathodic Arc-Deposited Ti and Cr Thin Films on Stainless Steel for Bipolar Plates
by Nils Fredebeul-Beverungen, Maximilian Steinhorst and Teja Roch
Materials 2024, 17(12), 2864; https://doi.org/10.3390/ma17122864 - 12 Jun 2024
Cited by 1 | Viewed by 846
Abstract
In this work, the potential of magnetron sputtering, as well as cathodic arc evaporation, is investigated with regard to its suitability as a bipolar plate coating of a PEM fuel cell. For this purpose, Cr and Ti thin films were deposited onto a [...] Read more.
In this work, the potential of magnetron sputtering, as well as cathodic arc evaporation, is investigated with regard to its suitability as a bipolar plate coating of a PEM fuel cell. For this purpose, Cr and Ti thin films were deposited onto a 0.1 mm SS316L by varying the power and bias voltage. The surface structure and thickness of the coatings are examined via SEM and tactile profilometry. Moreover, the coating variants are compared with each other based on the electrical and electrochemical properties relevant to bipolar plates. The sputtered Cr thin films achieve the lowest contact resistance values and exhibit a columnar structure with a smooth surface. Regarding the electrochemical properties, titanium deposited via cathodic arc evaporation has a low current density in the passive region and high breakthrough potential. All in all, both deposition techniques have their individual advantages for the preparation of bipolar plates’ coatings. However, Ti thin films prepared via cathodic arc seem to be the most suitable option due to the combination of a high deposition rate, a low cost and good coating properties. Full article
(This article belongs to the Special Issue Friction, Corrosion and Protection of Material Surfaces)
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12 pages, 2219 KiB  
Article
Phosphorus-Doping Enables the Superior Durability of a Palladium Electrocatalyst towards Alkaline Oxygen Reduction Reactions
by Wen-Yuan Zhao, Miao-Ying Chen, Hao-Ran Wu, Wei-Dong Li and Bang-An Lu
Materials 2024, 17(12), 2879; https://doi.org/10.3390/ma17122879 - 12 Jun 2024
Viewed by 907
Abstract
The sluggish kinetics of oxygen reduction reactions (ORRs) require considerable Pd in the cathode, hindering the widespread of alkaline fuel cells (AFCs). By alloying Pd with transition metals, the oxygen reduction reaction’s catalytic properties can be substantially enhanced. Nevertheless, the utilization of Pd-transition [...] Read more.
The sluggish kinetics of oxygen reduction reactions (ORRs) require considerable Pd in the cathode, hindering the widespread of alkaline fuel cells (AFCs). By alloying Pd with transition metals, the oxygen reduction reaction’s catalytic properties can be substantially enhanced. Nevertheless, the utilization of Pd-transition metal alloys in fuel cells is significantly constrained by their inadequate long-term durability due to the propensity of transition metals to leach. In this study, a nonmetallic doping strategy was devised and implemented to produce a Pd catalyst doped with P that exhibited exceptional durability towards ORRs. Pd3P0.95 with an average size of 6.41 nm was synthesized by the heat-treatment phosphorization of Pd nanoparticles followed by acid etching. After P-doping, the size of the Pd nanoparticles increased from 5.37 nm to 6.41 nm, and the initial mass activity (MA) of Pd3P0.95/NC reached 0.175 A mgPd−1 at 0.9 V, slightly lower than that of Pd/C. However, after 40,000 cycles of accelerated durability testing, instead of decreasing, the MA of Pd3P0.95/NC increased by 6.3% while the MA loss of Pd/C was 38.3%. The durability was primarily ascribed to the electronic structure effect and the aggregation resistance of the Pd nanoparticles. This research also establishes a foundation for the development of Pd-based ORR catalysts and offers a direction for the future advancement of catalysts designed for practical applications in AFCs. Full article
(This article belongs to the Section Materials Chemistry)
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14 pages, 5388 KiB  
Article
Additively-Manufactured Broadband Metamaterial-Based Luneburg Lens for Flexible Beam Scanning
by Xuanjing Li, Rui Feng, Quilin Tan, Jianjia Yi, Shixiong Wang, Feng He and Shah Nawaz Burokur
Materials 2024, 17(12), 2847; https://doi.org/10.3390/ma17122847 - 11 Jun 2024
Viewed by 1026
Abstract
Multi-beam microwave antennas have attracted enormous attention owing to their wide range of applications in communication systems. Here, we propose a broadband metamaterial-based multi-beam Luneburg lens-antenna with low polarization sensitivity. The lens is constructed from additively manufactured spherical layers, where the effective permittivity [...] Read more.
Multi-beam microwave antennas have attracted enormous attention owing to their wide range of applications in communication systems. Here, we propose a broadband metamaterial-based multi-beam Luneburg lens-antenna with low polarization sensitivity. The lens is constructed from additively manufactured spherical layers, where the effective permittivity of the constituting elements is obtained by adjusting the ratio of dielectric material to air. Flexible microstrip patch antennas operating at different frequencies are used as primary feeds illuminating the lens to validate the radiation features of the lens-antenna system. The proposed Luneburg lens-antenna achieves ±72° beam scanning angle over a broad frequency range spanning from 2 GHz to 8 GHz and presents a gain between 15.3 dBi and 22 dBi, suggesting potential applications in microwave- and millimeter-wave mobile communications, radar detection and remote sensing. Full article
(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))
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18 pages, 5494 KiB  
Article
Three-Dimensional-Printed Composite Structures: The Effect of LSCF Slurry Solid Loading, Binder, and Direct-Write Process Parameters
by Man Yang, Santosh Kumar Parupelli, Zhigang Xu and Salil Desai
Materials 2024, 17(12), 2822; https://doi.org/10.3390/ma17122822 - 10 Jun 2024
Cited by 1 | Viewed by 853
Abstract
In this research, a direct-write 3D-printing method was utilized for the fabrication of inter-digitized solid oxide fuel cells (SOFCs) using ceramic materials. The cathode electrode was fabricated using the LSCF (La0.6Sr0.2Fe0.8Co0.2O3-δ) slurry loading [...] Read more.
In this research, a direct-write 3D-printing method was utilized for the fabrication of inter-digitized solid oxide fuel cells (SOFCs) using ceramic materials. The cathode electrode was fabricated using the LSCF (La0.6Sr0.2Fe0.8Co0.2O3-δ) slurry loading and the Polyvinyl butyral (PVB) binder. The rheological parameters of slurries with varying LSCF slurry loading and PVB binder concentration were evaluated to determine their effect on the cathode trace performance in terms of microstructure, size, and resistance. Additionally, the dimensional shrinkage of LSCF lines after sintering was investigated to realize their influence on cathode line width and height. Moreover, the effect of the direct-write process parameters such as pressure, distance between the nozzle and substrate, and speed on the cathode line dimensions and resistance was evaluated. LSCF slurry with 50% solid loading, 12% binder, and 0.2% dispersant concentration was determined to be the optimal value for the fabrication of SOFCs using the direct-write method. The direct-write process parameters, in addition to the binder and LSCF slurry concentration ratios, had a considerable impact on the microstructure of cathode lines. Based on ANOVA findings, pressure and distance had significant effects on the cathode electrode resistance. An increase in the distance between the nozzle and substrate, speed, or extrusion pressure of the direct writing process increased the resistance of the cathode lines. These findings add to the ongoing effort to refine SOFC fabrication techniques, opening the avenues for advanced performance and efficiency of SOFCs in energy applications. Full article
(This article belongs to the Special Issue 3D-Printed Composite Structures: Design, Properties and Application)
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22 pages, 3109 KiB  
Article
Determination of Fluorine by Ion-Selective Electrode and High-Resolution Continuum Source Graphite Furnace Molecular Absorption Spectrometry with Respect to Animal Feed Safety
by Zofia Kowalewska, Karolina Goluch, Waldemar Korol, Rafał Olchowski and Ryszard Dobrowolski
Materials 2024, 17(12), 2812; https://doi.org/10.3390/ma17122812 - 9 Jun 2024
Viewed by 1113
Abstract
Fluorine, depending on its concentration and chemical form, is essential or toxic to humans and animals. Therefore, it is crucial to be able to determine it reliably. In this study, fluorine was determined in animal feed after extraction with HCl (gastric juice simulation). [...] Read more.
Fluorine, depending on its concentration and chemical form, is essential or toxic to humans and animals. Therefore, it is crucial to be able to determine it reliably. In this study, fluorine was determined in animal feed after extraction with HCl (gastric juice simulation). The standard potentiometric method with a fluoride-selective electrode (ISE) and newly developed high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GFMAS) method was applied. Feed samples turned out to be a challenge for HR-CS GFMAS. Chemical interferences (formation of competing molecules, CaF, GaCl, and GaP, instead of the target GaF molecule) and spectral effects (including a phosphorous molecule spectrum and atomic lines) were identified. An additional difficulty was caused by reagent contamination with F and memory effects. Difficulties were eliminated/reduced. The quality of ISE analysis was multi-directionally verified (including comprehensive proficiency testing). A risk of inaccuracy at low F concentration, where the calibration relationship is nonlinear, was investigated. The results of both methods were consistent, which confirms the accuracy of the methods and informs that the extracted fluorine is in fluoride form. The results of extensive ISE tests conducted in Poland in 2021–2023 have shown that, in most cases, the fluoride content is significantly lower than the threshold values. Full article
(This article belongs to the Special Issue Electrochemical Material Science and Electrode Processes)
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12 pages, 3520 KiB  
Article
Comparative Study for Propranolol Adsorption on the Biochars from Different Agricultural Solid Wastes
by Wenjie Nie, Qianqian Che, Danni Chen, Hongyu Cao and Yuehua Deng
Materials 2024, 17(12), 2793; https://doi.org/10.3390/ma17122793 - 7 Jun 2024
Cited by 1 | Viewed by 666
Abstract
Currently, large amounts of agricultural solid wastes have caused serious environmental problems. Agricultural solid waste is made into biochar by pyrolysis, which is an effective means of its disposal. As the prepared biochar has a good adsorption capacity, it is often used to [...] Read more.
Currently, large amounts of agricultural solid wastes have caused serious environmental problems. Agricultural solid waste is made into biochar by pyrolysis, which is an effective means of its disposal. As the prepared biochar has a good adsorption capacity, it is often used to treat pollutants in water, such as heavy metals and pharmaceuticals. PRO is an emerging contaminant in the environment today. However, there are limited studies on the interaction between biochars with PRO. Thus, in this study, we investigate the adsorption of PRO onto the biochars derived from three different feedstocks. The order of adsorption capacity was corn stalk biochar (CS, 10.97 mg/g) > apple wood biochar (AW, 10.09 mg/g) > rice husk biochar (RH, 8.78 mg/g). When 2 < pH < 9, the adsorption capacity of all the biochars increased as the pH increased, while the adsorption decreased when pH > 9, 10 and 10.33 for AW, CS and RH, respectively. The adsorption of PRO on biochars was reduced with increasing Na+ and Ca2+ concentrations from 0 to 200 mg·L−1. The effects of pH and coexisting ions illustrated that there exist electrostatic interaction and cation exchange in the process. In addition, when HA concentration was less than 20 mg/L, it promoted the adsorption of PRO on the biochars; however, when the concentration was more than 20 mg/L, its promoting effect was weakened and gradually changed into an inhibitory effect. The adsorption isotherm data of PRO by biochars were best fitted with the Freundlich model, indicating that the adsorption process is heterogeneous adsorption. The adsorption kinetics were fitted well with the pseudo-second-order model. All the results can provide new information into the adsorption behavior of PRO and the biochars in the aquatic environment and a theoretical basis for the large-scale application of biochar from agricultural solid wastes. Full article
(This article belongs to the Special Issue Adsorption Materials and Their Applications)
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24 pages, 5331 KiB  
Review
Material Extrusion Additive Manufacturing of Ceramics: A Review on Filament-Based Process
by Roberto Spina and Luigi Morfini
Materials 2024, 17(11), 2779; https://doi.org/10.3390/ma17112779 - 6 Jun 2024
Cited by 1 | Viewed by 1517
Abstract
Additive manufacturing is very important due to its potential to build components and products using high-performance materials. The filament-based 3D printing of ceramics is investigated, revealing significant developments and advancements in ceramic material extrusion technology in recent years. Researchers employ several typologies of [...] Read more.
Additive manufacturing is very important due to its potential to build components and products using high-performance materials. The filament-based 3D printing of ceramics is investigated, revealing significant developments and advancements in ceramic material extrusion technology in recent years. Researchers employ several typologies of ceramics and binders to achieve fully dense products. The design of the filament and the necessary technological adaptations for 3D printing are fully investigated. From a material perspective, this paper reviews and analyzes the recent developments in additive manufacturing of material-extruded ceramics products, pointing out the performance and properties achieved with different material-binder combinations. The main gaps to be filled and recommendations for future developments in this field are reported. Full article
(This article belongs to the Special Issue Advances in 3D Printing/Additive Manufacturing Technology of Materials)
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17 pages, 17573 KiB  
Article
Revisiting Electronic Topological Transitions in the Silver–Palladium (AgcPd1−c) Solid Solution: An Experimental and Theoretical Investigation
by Florian Reiter, Alberto Marmodoro, Andrei Ionut Mardare, Cezarina Cela Mardare, Achim Walter Hassel, Arthur Ernst and Martin Hoffmann
Materials 2024, 17(11), 2743; https://doi.org/10.3390/ma17112743 - 4 Jun 2024
Cited by 1 | Viewed by 1083
Abstract
Multiple thick film samples of the AgcPd1−c solid solution were prepared using physical vapour deposition over a borosilicate glass substrate. This synthesis technique allows continuous variation in stoichiometry, while the distribution of silver or palladium atoms retains the [...] Read more.
Multiple thick film samples of the AgcPd1−c solid solution were prepared using physical vapour deposition over a borosilicate glass substrate. This synthesis technique allows continuous variation in stoichiometry, while the distribution of silver or palladium atoms retains the arrangement into an on-average periodic lattice with smoothly varying unit cell parameters. The alloy concentration and geometry were measured over a set of sample points, respectively, via energy-dispersive X-ray spectroscopy and via X-ray diffraction. These results are compared with ab initio total energy and electronic structure calculations based on density functional theory, and using the coherent potential approximation for an effective medium description of disorder. The theoretically acquired lattice parameters appear in qualitative agreement with the measured trends. The numerical study of the Fermi surface also shows a variation in its topological features, which follow the change in silver concentration. These were related to the electrical resistivity of the AgcPd1−c alloy. The theoretically obtained variation exhibits a significant correlation with nonlinear changes in the resistivity as a function of composition. This combined experimental and theoretical study suggests the possibility of using resistivity measurements along concentration gradients as a way to gain some microscopic insight into the electronic structure of an alloy. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Materials Physics)
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15 pages, 5009 KiB  
Article
Strength of Composite Pressure Insulators for High Voltage Circuit Breakers: An Experimental and Numerical Investigation
by Jan Ferino, Gabriela Loi, Andrea Meleddu, Francesco Aymerich, Iuri Mazzarelli and Elisa Pichini
Materials 2024, 17(11), 2741; https://doi.org/10.3390/ma17112741 - 4 Jun 2024
Viewed by 733
Abstract
Glass fiber-reinforced composite cylinders, capable of withstanding internal pressure generated during service, are increasingly utilized as insulators in high voltage circuit breakers. Different testing procedures have been suggested by various standards to assess the pressure resistance of these components. Due to its simplicity [...] Read more.
Glass fiber-reinforced composite cylinders, capable of withstanding internal pressure generated during service, are increasingly utilized as insulators in high voltage circuit breakers. Different testing procedures have been suggested by various standards to assess the pressure resistance of these components. Due to its simplicity and cost-effectiveness, the split-disk testing method is the most widely used for evaluating the hoop strength of pressure cylinders during the development and verification phases. However, the method presents several aspects, such as those related to the influence of specimen geometry and friction, which require further examination since they may impact the outcome of the experimental tests. The investigation, carried out by a combination of experimental testing and finite element analyses, shows that the friction between the specimen and the semi-disks has a noteworthy effect on the hoop load applied to the specimen. Almost constant load distributions along the hoop direction, representative of the real operating conditions in a pressurized cylinder, can be achieved via proper lubrication of the contact surfaces. Furthermore, FE analyses demonstrate that the notch geometry suggested by specific standards (short notch) is not capable of inducing a uniform strain distribution in the notched region. A different notch geometry (long notch) is proposed in the study to attain a more uniform strain field over the reduced area region. The experimental results indicate that the strength measured on the short notch specimens is higher than that determined on the long notch specimens, thus confirming the significant influence of strain distribution on the strength properties measured with the split-disk method. Full article
(This article belongs to the Special Issue Mechanical Behaviour of Advanced Metal and Composite Materials)
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11 pages, 5044 KiB  
Article
Mo-Doped Na4Fe3(PO4)2P2O7/C Composites for High-Rate and Long-Life Sodium-Ion Batteries
by Tongtong Chen, Xianying Han, Mengling Jie, Zhiwu Guo, Jiangang Li and Xiangming He
Materials 2024, 17(11), 2679; https://doi.org/10.3390/ma17112679 - 1 Jun 2024
Viewed by 1765
Abstract
Na4Fe3(PO4)2P2O7/C (NFPP) is a promising cathode material for sodium-ion batteries, but its electrochemical performance is heavily impeded by its low electronic conductivity. To address this, pure-phase Mo6+-doped Na4 [...] Read more.
Na4Fe3(PO4)2P2O7/C (NFPP) is a promising cathode material for sodium-ion batteries, but its electrochemical performance is heavily impeded by its low electronic conductivity. To address this, pure-phase Mo6+-doped Na4Fe3−xMox(PO4)2P2O7/C (Mox-NFPP, x = 0, 0.05, 0.10, 0.15) with the Pn21a space group is successfully synthesized through spray drying and annealing methods. Density functional theory (DFT) calculations reveal that Mo6+ doping facilitates the transition of electrons from the valence to the conduction band, thus enhancing the intrinsic electron conductivity of Mox-NFPP. With an optimal Mo6+ doping level of x = 0.10, Mo0.10-NFPP exhibits lower charge transfer resistance, higher sodium-ion diffusion coefficients, and superior rate performance. As a result, the Mo0.10-NFPP cathode offers an initial discharge capacity of up to 123.9 mAh g−1 at 0.1 C, nearly reaching its theoretical capacity. Even at a high rate of 10 C, it delivers a high discharge capacity of 86.09 mAh g−1, maintaining 96.18% of its capacity after 500 cycles. This research presents a new and straightforward strategy to enhance the electrochemical performance of NFPP cathode materials for sodium-ion batteries. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Materials Chemistry)
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8 pages, 1369 KiB  
Article
Separation of Adjacent Light Rare Earth Elements Using Silica Gel Modified with Diglycolamic Acid
by Takeshi Ogata and Hirokazu Narita
Materials 2024, 17(11), 2648; https://doi.org/10.3390/ma17112648 - 30 May 2024
Viewed by 799
Abstract
The separation of adjacent rare earth elements (REEs) is a challenging issue due to their chemical similarity. We have investigated the separation of adjacent REEs using four types of adsorbents consisting of silica gel modified with diglycolamic acid with different functional groups at [...] Read more.
The separation of adjacent rare earth elements (REEs) is a challenging issue due to their chemical similarity. We have investigated the separation of adjacent REEs using four types of adsorbents consisting of silica gel modified with diglycolamic acid with different functional groups at the amide position. For all the adsorbents, the adsorption ratio of REEs increased with the increase in atomic number from La to Sm and then became constant for heavy REEs. Among them, EDASiDGA, an adsorbent containing secondary and tertiary amides, showed a high separation factor for Nd/Pr of 2.8. The EDASiDGA-packed column was tested for individual recovery of Pr, Nd, and Sm. After the adsorption of these REEs from 0.10 M HCl, desorption tests were performed with 0.32 and 1.0 M HCl. As a result, Pr and Nd were eluted separately with 0.32 M HCl, and Sm was recovered with 1.0 M HCl. Since the EDASiDGA-packed column showed excellent separation of Pr/Nd/Sm without any chelating agent, it is promising for practical use. Full article
(This article belongs to the Special Issue New Trends of Functional Materials for Wastewater Treatment Applications)
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13 pages, 3508 KiB  
Article
Influence of Carbon Source on the Buffer Layer for 4H-SiC Homoepitaxial Growth
by Shangyu Yang, Ning Guo, Siqi Zhao, Yunkai Li, Moyu Wei, Yang Zhang and Xingfang Liu
Materials 2024, 17(11), 2612; https://doi.org/10.3390/ma17112612 - 29 May 2024
Viewed by 927
Abstract
In this study, we systematically explore the impact of C/Si ratio, pre-carbonization time, H2 etching time, and growth pressure on the buffer layer and subsequent epitaxial layer of 6-inch 4H-SiC wafers. Our findings indicate that the buffer layer’s C/Si ratio and growth [...] Read more.
In this study, we systematically explore the impact of C/Si ratio, pre-carbonization time, H2 etching time, and growth pressure on the buffer layer and subsequent epitaxial layer of 6-inch 4H-SiC wafers. Our findings indicate that the buffer layer’s C/Si ratio and growth pressure significantly influence the overall quality of the epitaxial wafer. Specifically, an optimal C/Si ratio of 0.5 and a growth pressure of 70 Torr yield higher-quality epitaxial layers. Additionally, the pre-carbonization time and H2 etching time primarily affect the uniformity and surface quality of the epitaxial wafer, with a pre-carbonization time of 3 s and an H2 etching time of 3 min found to enhance the surface quality of the epitaxial layer. Full article
(This article belongs to the Special Issue Chemical Vapor Deposition (CVD) Techniques in Materials Science for Electronic Devices Applications)
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14 pages, 1216 KiB  
Article
Crystal Structure Complexity and Approximate Limits of Possible Crystal Structures Based on Symmetry-Normalized Volumes
by Oliver Tschauner and Marko Bermanec
Materials 2024, 17(11), 2618; https://doi.org/10.3390/ma17112618 - 29 May 2024
Cited by 1 | Viewed by 671
Abstract
Rules that control the arrangement of chemical species within crystalline arrays of different symmetry and structural complexity are of fundamental importance in geoscience, material science, physics, and chemistry. Here, the volume of crystal phases is normalized by their ionic volume and an algebraic [...] Read more.
Rules that control the arrangement of chemical species within crystalline arrays of different symmetry and structural complexity are of fundamental importance in geoscience, material science, physics, and chemistry. Here, the volume of crystal phases is normalized by their ionic volume and an algebraic index that is based on their space-group and crystal site symmetries. In correlation with the number of chemical formula units Z, the normalized volumes exhibit upper and lower limits of possible structures. A bottleneck of narrowing limits occurs for Z around 80 to 100, but the field of allowed crystalline configurations widens above 100 due to a change in the slope of the lower limit. For small Z, the highest count of structures is closer to the upper limit, but at large Z, most materials assume structures close to the lower limit. In particular, for large Z, the normalized volume provides rather narrow constraints for the prediction of novel crystalline phases. In addition, an index of higher and lower complexity of crystalline phases is derived from the normalized volume and tested against key criteria. Full article
(This article belongs to the Special Issue Development and Application of Advanced Inorganic Composites)
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24 pages, 11296 KiB  
Review
How to Improve the Curing Ability during the Vat Photopolymerization 3D Printing of Non-Oxide Ceramics: A Review
by Xiong Gao, Jingyi Chen, Xiaotong Chen, Wenqing Wang, Zengchan Li and Rujie He
Materials 2024, 17(11), 2626; https://doi.org/10.3390/ma17112626 - 29 May 2024
Cited by 2 | Viewed by 1100
Abstract
Vat photopolymerization (VP), as an additive manufacturing process, has experienced significant growth due to its high manufacturing precision and excellent surface quality. This method enables the fabrication of intricate shapes and structures while mitigating the machining challenges associated with non-oxide ceramics, which are [...] Read more.
Vat photopolymerization (VP), as an additive manufacturing process, has experienced significant growth due to its high manufacturing precision and excellent surface quality. This method enables the fabrication of intricate shapes and structures while mitigating the machining challenges associated with non-oxide ceramics, which are known for their high hardness and brittleness. Consequently, the VP process of non-oxide ceramics has emerged as a focal point in additive manufacturing research areas. However, the absorption, refraction, and reflection of ultraviolet light by non-oxide ceramic particles can impede light penetration, leading to reduced curing thickness and posing challenges to the VP process. To enhance the efficiency and success rate of this process, researchers have explored various aspects, including the parameters of VP equipment, the composition of non-oxide VP slurries, and the surface modification of non-oxide particles. Silicon carbide and silicon nitride are examples of non-oxide ceramic particles that have been successfully employed in VP process. Nonetheless, there remains a lack of systematic induction regarding the curing mechanisms and key influencing factors of the VP process in non-oxide ceramics. This review firstly describes the curing mechanism of the non-oxide ceramic VP process, which contains the chain initiation, chain polymerization, and chain termination processes of the photosensitive resin. After that, the impact of key factors on the curing process, such as the wavelength and power of incident light, particle size, volume fraction of ceramic particles, refractive indices of photosensitive resin and ceramic particles, incident light intensity, critical light intensity, and the reactivity of photosensitive resins, are systematically discussed. Finally, this review discusses future prospects and challenges in the non-oxide ceramic VP process. Its objective is to offer valuable insights and references for further research into non-oxide ceramic VP processes. Full article
(This article belongs to the Special Issue Advances in 3D Printing/Additive Manufacturing Technology of Materials)
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