Materials

13 pages, 5692 KiB

Open AccessEditor’s ChoiceArticle

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 611

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

Open AccessEditor’s ChoiceArticle

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 580

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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63 pages, 16763 KiB

Open AccessEditor’s ChoiceReview

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 1580

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

Open AccessEditor’s ChoiceArticle

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 606

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

Open AccessEditor’s ChoiceArticle

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 957

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

Open AccessEditor’s ChoiceArticle

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 786

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

Open AccessEditor’s ChoiceArticle

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 710

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

Open AccessEditor’s ChoiceArticle

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 822

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

μ

m and 200

μ

m dielectric thicknesses. A maximal out-of-plane displacement of 500

μ

m 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

Open AccessEditor’s ChoiceArticle

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 1 | Viewed by 1059

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 (V_OC) of 98 V and a short-circuit current (I_SC) 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

Open AccessEditor’s ChoiceArticle

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 931

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

Open AccessEditor’s ChoiceArticle

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

Viewed by 843

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

Open AccessEditor’s ChoiceArticle

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 1237

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

Open AccessEditor’s ChoiceArticle

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 1190

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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91 pages, 19320 KiB

Open AccessEditor’s ChoiceReview

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 1651

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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25 pages, 11093 KiB

Open AccessEditor’s ChoiceArticle

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 673

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 (f_L) and residual flexural strength (f_R,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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11 pages, 10922 KiB

Open AccessEditor’s ChoiceArticle

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 961

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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20 pages, 4483 KiB

Open AccessEditor’s ChoiceArticle

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 1108

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 K_d (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

Open AccessEditor’s ChoiceReview

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 1034

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 (d_ij) 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 (d_ij) of single crystals, thin films, and dimension-tuned halide perovskites based on different measurement methods. Our study finds that the (d_ij) 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 (d_ij) coefficient is dominantly measured by the PFM technique. The reported values of d_ij 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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18 pages, 5495 KiB

Open AccessEditor’s ChoiceArticle

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 829

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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13 pages, 2343 KiB

Open AccessEditor’s ChoiceArticle

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 868

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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16 pages, 2744 KiB

Open AccessEditor’s ChoiceArticle

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 3 | Viewed by 1241

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))_0.9Cs_0.1PbI₃), and analyzed the 85 °C thermal stability followed by the ISOS-D-2 protocol. Without encapsulation, FA_0.9Cs_0.1PbI₃ 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 FA_0.9Cs_0.1PbI₃) 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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14 pages, 5499 KiB

Open AccessEditor’s ChoiceArticle

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

Viewed by 767

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

Open AccessEditor’s ChoiceArticle

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 823

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. Pd₃P_0.95 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 Pd₃P_0.95/NC reached 0.175 A mg_Pd⁻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 Pd₃P_0.95/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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18 pages, 5494 KiB

Open AccessEditor’s ChoiceArticle

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 792

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 (La_0.6Sr_0.2Fe_0.8Co_0.2O_3-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 (La_0.6Sr_0.2Fe_0.8Co_0.2O_3-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

Open AccessEditor’s ChoiceArticle

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 984

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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24 pages, 5331 KiB

Open AccessEditor’s ChoiceReview

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 1250

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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15 pages, 5009 KiB

Open AccessEditor’s ChoiceArticle

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 673

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

Open AccessEditor’s ChoiceArticle

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 1524

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 Na₄Fe_3−xMo_x(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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13 pages, 3508 KiB

Open AccessEditor’s ChoiceArticle

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 857

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

Open AccessEditor’s ChoiceArticle

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

Viewed by 613

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

Open AccessEditor’s ChoiceReview

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 965

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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23 pages, 5007 KiB

Open AccessEditor’s ChoiceArticle

Effect of the Atmospheric Plasma Treatment Parameters on the Surface and Mechanical Properties of Carbon Fabric

by Samuele Sampino, Raffaele Ciardiello, Domenico D’Angelo, Laura Cagna and Davide Salvatore Paolino

Materials 2024, 17(11), 2547; https://doi.org/10.3390/ma17112547 - 25 May 2024

Viewed by 1114

Abstract

The use of Atmospheric Pressure Plasma Jet (APPJ) technology for surface treatment of carbon fabrics is investigated to estimate the increase in the fracture toughness of carbon-fiber composite materials. Nitrogen and a nitrogen–hydrogen gas mixture were used to size the carbon fabrics by [...] Read more.

The use of Atmospheric Pressure Plasma Jet (APPJ) technology for surface treatment of carbon fabrics is investigated to estimate the increase in the fracture toughness of carbon-fiber composite materials. Nitrogen and a nitrogen–hydrogen gas mixture were used to size the carbon fabrics by preliminarily optimizing the process parameters. The effects of the APPJ on the carbon fabrics were investigated by using optical and chemical characterizations. Optical Emission Spectroscopy, Fourier Transform Infrared-Attenuated Total Reflection, X-ray Photoelectron Spectroscopy and micro-Raman spectroscopy were adopted to assess the effectiveness of ablation and etching effects of the treatment, in terms of grafting of new functional groups and active sites. The treated samples showed an increase in chemical groups grafted onto the surfaces, and a change in carbon structure was influential in the case of chemical interaction with epoxy groups of the epoxy resin adopted. Flexural test, Double Cantilever Beam and End-Notched Flexure tests were then carried out to characterize the composite and evaluate the fracture toughness in Mode I and Mode II, respectively. N₂/H₂ specimens showed significant increases in G_IC and G_IIC, compared to the untreated specimens, and slight increases in P_max at the first crack propagation. Full article

(This article belongs to the Special Issue Mechanical Properties, Structural Design and Applications of Carbon-Fiber Composites)

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18 pages, 12303 KiB

Open AccessEditor’s ChoiceArticle

Optimization of Magnetic Tunnel Junction Structure through Component Analysis and Deposition Parameters Adjustment

by Crina Ghemes, Mihai Tibu, Oana-Georgiana Dragos-Pinzaru, Gabriel Ababei, George Stoian, Nicoleta Lupu and Horia Chiriac

Materials 2024, 17(11), 2554; https://doi.org/10.3390/ma17112554 - 25 May 2024

Viewed by 899

Abstract

In this work, we focus on a detailed study of the role of each component layer in the multilayer structure of a magnetic tunnel junction (MTJ) as well as the analysis of the effects that the deposition parameters of the thin films have [...] Read more.

In this work, we focus on a detailed study of the role of each component layer in the multilayer structure of a magnetic tunnel junction (MTJ) as well as the analysis of the effects that the deposition parameters of the thin films have on the performance of the structure. Various techniques including atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to investigate the effects of deposition parameters on the surface roughness and thickness of individual layers within the MTJ structure. Furthermore, this study investigates the influence of thin films thickness on the magnetoresistive properties of the MTJ structure, focusing on the free ferromagnetic layer and the barrier layer (MgO). Through systematic analysis and optimization of the deposition parameters, this study demonstrates a significant improvement in the tunnel magnetoresistance (TMR) of the MTJ structure of 10% on average, highlighting the importance of precise control over thin films properties for enhancing device performance. Full article

(This article belongs to the Special Issue Preparation of Thin Films by PVD/CVD Deposition Techniques)

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15 pages, 9413 KiB

Open AccessEditor’s ChoiceArticle

Experimental and Numerical Investigation of the Use of Ultrasonic Waves to Assist Laser Welding

by Mohamad Salimi, Ahmed Teyeb, Evelyne El Masri, Samiul Hoque, Phil Carr, Wamadeva Balachandran and Tat-Hean Gan

Materials 2024, 17(11), 2521; https://doi.org/10.3390/ma17112521 - 23 May 2024

Cited by 1 | Viewed by 987

Abstract

This study evaluates the enhancement of laser welding using ultrasonic waves aimed at reorganising the intermetallic position in such a fashion that leads to increased mechanical properties of welds in battery pack assemblies for electric vehicles. The experiment employed 20 kHz and 40 [...] Read more.

This study evaluates the enhancement of laser welding using ultrasonic waves aimed at reorganising the intermetallic position in such a fashion that leads to increased mechanical properties of welds in battery pack assemblies for electric vehicles. The experiment employed 20 kHz and 40 kHz High-Power Ultrasound Transducers (HPUTs) in both contact and contactless modes. A simplified experimental configuration is suggested to represent conditions similar to those found in electric vehicle battery pack assemblies. Measurements of vibration transmission to aluminium alloy 1050 plates revealed more than a 1000-fold increase in acceleration amplitude in contact mode compared to contactless mode. The 20 kHz transducer in contactless mode demonstrated superior performance, showing a 10% increase in load and 27% increase in extension compared to welding without ultrasonic assistance. On the other hand, the 40 kHz transducer, while still improved over non-ultrasonic methods, showed less pronounced benefits. This suggests that lower-frequency ultrasonic assistance (20 kHz) is more effective in this specific context. The study explores ultrasonic assistance in laser welding copper (Cu101) to aluminium alloy 1050 using 20 kHz and 40 kHz HPUTs, showing that both transducers enhance microstructural integrity by reducing copper homogenisation into aluminium, with the 20 kHz frequency proving more effective in this context. A numerical simulation was conducted to evaluate the transmission of pressure into the molten pool of the weld, correlated with the vibration results obtained from the 20 kHz transducer. The numerical simulation confirms that no cavitation is initiated in the molten pool area, and all improvements are solely due to the ultrasonic waves. Full article

(This article belongs to the Special Issue Ultrasound for Material Characterization and Processing (3rd Edition))

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10 pages, 1882 KiB

Open AccessEditor’s ChoiceArticle

Research on Evolution of Relevant Defects in Heavily Mg-Doped GaN by H Ion Implantation Followed by Thermal Annealing

by Zonglin Jiang, Dan Yan, Ning Zhang, Junxi Wang and Xuecheng Wei

Materials 2024, 17(11), 2518; https://doi.org/10.3390/ma17112518 - 23 May 2024

Viewed by 779

Abstract

This study focuses on the heavily Mg-doped GaN in which the passivation effect of hydrogen and the compensation effect of nitrogen vacancies (V_N) impede its further development. To investigate those two factors, H ion implantation followed by thermal annealing was performed [...] Read more.

This study focuses on the heavily Mg-doped GaN in which the passivation effect of hydrogen and the compensation effect of nitrogen vacancies (V_N) impede its further development. To investigate those two factors, H ion implantation followed by thermal annealing was performed on the material. The evolution of relevant defects (H and V_N) was revealed, and their distinct behaviors during thermal annealing were compared between different atmospheres (N₂/NH₃). The concentration of H and its associated yellow luminescence (YL) band intensity decrease as the thermal annealing temperature rises, regardless of the atmosphere being N₂ or NH₃. However, during thermal annealing in NH₃, the decrease in H concentration is notably faster compared to N₂. Furthermore, a distinct trend is observed in the behavior of the blue luminescence (BL) band under N₂ and NH₃. Through a comprehensive analysis of surface properties, we deduce that the decomposition of NH₃ during thermal annealing not only promotes the out-diffusion of H ions from the material, but also facilitates the repair of V_N on the surface of heavily Mg-doped GaN. This research could provide crucial insights into the post-growth process of heavily Mg-doped GaN. Full article

(This article belongs to the Section Electronic Materials)

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15 pages, 7502 KiB

Open AccessEditor’s ChoiceArticle

Rheological Properties and 3D Printing Behavior of PCL and DMSO₂ Composites for Bio-Scaffold

by Jae-Won Jang, Kyung-Eun Min, Cheolhee Kim, Chien Wern and Sung Yi

Materials 2024, 17(10), 2459; https://doi.org/10.3390/ma17102459 - 20 May 2024

Cited by 2 | Viewed by 1001

Abstract

The significance of rheology in the context of bio three-dimensional (3D) printing lies in its impact on the printing behavior, which shapes material flow and the layer-by-layer stacking process. The objective of this study is to evaluate the rheological and printing behaviors of [...] Read more.

The significance of rheology in the context of bio three-dimensional (3D) printing lies in its impact on the printing behavior, which shapes material flow and the layer-by-layer stacking process. The objective of this study is to evaluate the rheological and printing behaviors of polycaprolactone (PCL) and dimethyl sulfone (DMSO₂) composites. The rheological properties were examined using a rotational rheometer, employing a frequency sweep test. Simultaneously, the printing behavior was investigated using a material extrusion 3D printer, encompassing varying printing temperatures and pressures. Across the temperature range of 120–140 °C, both PCL and PCL/DMSO₂ composites demonstrated liquid-like behavior, with a higher loss modulus than storage modulus. This behavior exhibited shear-thinning characteristics. The addition of DMSO₂ 10, 20, and 30 wt% into the PCL matrix reduced a zero-shear viscosity of 33, 46, and 74% compared to PCL, respectively. The materials exhibited extrusion velocities spanning from 0.0850 to 6.58 mm/s, with velocity being governed by the reciprocal of viscosity. A significant alteration in viscosity by temperature change directly led to a pronounced fluctuation in extrusion velocity. Extrusion velocities below 0.21 mm/s led to the production of unstable printed lines. The presence of distinct viscosities altered extrusion velocity, flow rate, and strut diameter. This phenomenon allowed the categorization of pore shape into three zones: irregular, normal, and no-pore zones. It underscored the importance of comprehending the rheological aspects of biomaterials in enhancing the overall quality of bio-scaffolds during the 3D printing process. Full article

(This article belongs to the Special Issue Advanced Materials and Manufacturing Processes)

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12 pages, 6907 KiB

Open AccessEditor’s ChoiceArticle

Flexible Nanofiber Pressure Sensors with Hydrophobic Properties for Wearable Electronics

by Yang Liu, Baoxiu Wang, Jiapeng Chen, Min Zhu and Zhenlin Jiang

Materials 2024, 17(10), 2463; https://doi.org/10.3390/ma17102463 - 20 May 2024

Cited by 1 | Viewed by 1031

Abstract

In recent years, flexible pressure sensors have received considerable attention for their potential applications in health monitoring and human–machine interfaces. However, the development of flexible pressure sensors with excellent sensitivity performance and a variety of advantageous characteristics remains a significant challenge. In this [...] Read more.

In recent years, flexible pressure sensors have received considerable attention for their potential applications in health monitoring and human–machine interfaces. However, the development of flexible pressure sensors with excellent sensitivity performance and a variety of advantageous characteristics remains a significant challenge. In this paper, a high-performance flexible piezoresistive pressure sensor, BC/ZnO, is developed with a sensitive element consisting of bacterial cellulose (BC) nanofibrous aerogel modified by ZnO nanorods. The BC/ZnO pressure sensor exhibits excellent mechanical and hydrophobic properties, as well as a high sensitivity of −15.93 kPa⁻¹ and a wide range of detection pressure (0.3–20 kPa), fast response (300 ms), and good cyclic durability (>1000). Furthermore, the sensor exhibits excellent sensing performance in real-time monitoring of a wide range of human behaviors, including mass movements and subtle physiological signals. Full article

(This article belongs to the Section Smart Materials)

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23 pages, 6508 KiB

Open AccessEditor’s ChoiceArticle

The Influence of the Alkylamino Group on the Solvatochromic Behavior of 5-(4-substituted-arylidene)-1,3-dimethylpyrimidine-2,4,6-triones: Synthesis, Spectroscopic and Computational Studies

by Ilona Pyszka, Przemysław Krawczyk and Beata Jędrzejewska

Materials 2024, 17(10), 2447; https://doi.org/10.3390/ma17102447 - 19 May 2024

Cited by 1 | Viewed by 744

Abstract

Advances in electronics and medical diagnostics have made organic dyes extremely popular as key functional materials. From a practical viewpoint, it is necessary to assess the spectroscopic and physicochemical properties of newly designed dyes. In this context, the condensation of 1,3-dimethylbarbituric acid with [...] Read more.

Advances in electronics and medical diagnostics have made organic dyes extremely popular as key functional materials. From a practical viewpoint, it is necessary to assess the spectroscopic and physicochemical properties of newly designed dyes. In this context, the condensation of 1,3-dimethylbarbituric acid with electron-rich alkylaminobenzaldehyde derivatives has been described, resulting in a series of merocyanine-type dyes. These dyes exhibit intense blue-light absorption but weak fluorescence. An electron-donating alkylamino group at position C4 is responsible for the solvatochromic behavior of the dyes since the lone electron pair of the nitrogen atom is variably delocalized toward the barbituric ring, which exhibits electron-withdrawing properties. This was elucidated, taking into account the different geometry of the amino group. The intramolecular charge transfer in the molecules is responsible for the relatively high redshift in absorption and fluorescence spectra. Additionally, an increase in solvent polarity moves the absorption and fluorescence to lower energy regions. The observed solvatochromism is discussed in terms of the four-parameter Catalán solvent polarity scale. The differences in the behavior of the dyes were quantified with the aid of time-dependent density functional theory calculations. The obtained results made it possible to find regularities linking the basic spectroscopic properties of the compounds with their chemical structure. This is important in the targeted search for new, practically important dyes. Full article

(This article belongs to the Special Issue Size-Dependent Effects in Materials for Environmental Protection and Energy Application (2nd Edition))

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12 pages, 4077 KiB

Open AccessEditor’s ChoiceArticle

First-Principles Study of Discharge Products and Their Stability for Lithium-Nitrogen Batteries

by Guoxiong Qu, Xudong Zhao, Chengdong Wei, Hongyi Zhang, Yutong Yang, Hongtao Xue and Fuling Tang

Materials 2024, 17(10), 2429; https://doi.org/10.3390/ma17102429 - 18 May 2024

Viewed by 922

Abstract

Li-N₂ batteries present a relatively novel approach to N₂ immobilization, and an advanced N₂/Li₃N cycling method is introduced in this study. The low operating overpotential of metal–air batteries is quite favorable to their stable cycling performance, providing [...] Read more.

Li-N₂ batteries present a relatively novel approach to N₂ immobilization, and an advanced N₂/Li₃N cycling method is introduced in this study. The low operating overpotential of metal–air batteries is quite favorable to their stable cycling performance, providing a prospect for the development of a new type of battery with extreme voltage. The battery system of Li-N₂ uses N₂ as the positive electrode, lithium metal as the negative electrode, and a conductive medium containing soluble lithium salts as the electrolyte. In accordance with its voltage-distribution trend, a variety of lithium-nitrogen molecule intermediates are produced during the discharge process. There is a lack of theoretical description of material changes at the microscopic level during the discharge process. In this paper, the first-principles approach is used to simulate and analyze possible material changes during the discharge process of Li-N₂ batteries. The discharge process is simulated on a 4N-graphene anode substrate model, and simulations of its electrostatic potential, Density of States (DOS), HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) aspects confirm that the experimentally found Li₃N becomes the final stabilized product of the Li-N₂ battery. It can also be seen in the density of states that graphene with adsorption of 4N transforms from semiconducting to metallic properties. In addition, the differential charge also indicates that the Li-N₂ material has a strong adsorption effect on the substrate, which can play the dual role of electricity storage and nitrogen fixation. Full article

(This article belongs to the Special Issue Advanced Electrode Materials for Batteries)

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13 pages, 10556 KiB

Open AccessEditor’s ChoiceArticle

Influence of HiPIMS Pulse Widths on the Structure and Properties of Copper Films

by Xincheng Liu, Heda Bai, Yongjie Ren, Jin Li and Xiangli Liu

Materials 2024, 17(10), 2342; https://doi.org/10.3390/ma17102342 - 15 May 2024

Viewed by 952

Abstract

High-power pulse magnetron sputtering is a new type of magnetron sputtering technology that has advantages such as high peak power density and a high ionization rate compared to DC magnetron sputtering. In this paper, we report the effects of different pulse widths on [...] Read more.

High-power pulse magnetron sputtering is a new type of magnetron sputtering technology that has advantages such as high peak power density and a high ionization rate compared to DC magnetron sputtering. In this paper, we report the effects of different pulse widths on the current waveform and plasma spectrum of target material sputtering, as well as the structure and properties of Cu films prepared under the same sputtering voltage and duty cycle. Extending the pulse width can make the sputtering enter the self-sputtering (SS) stage and improve the ion quantity of sputtered particles. The Cu film prepared by HiPIMS with long pulse width has higher bond strength and lower electrical resistivity compared to the Cu film prepared by short pulse width. In terms of microstructure, the Cu film prepared by HiPIMS with the long pulse width has a larger grain size and lower micro-surface roughness. When the pulse width is bigger than 200 μs, the microstructure of the Cu film changes from granular to branched. This transformation reduces the interface on the Cu film, further reducing the resistivity of the Cu film. Compared to short pulses, long pulse width HiPIMS can obtain higher quality Cu films. This result provides a new process approach for preparing high-quality Cu films using HiPIMS technology. Full article

(This article belongs to the Special Issue Advances in Thin Films Materials: Properties, Characterization, Physical Vapor Deposition and Application)

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14 pages, 5421 KiB

Open AccessEditor’s ChoiceArticle

Microwave-Assisted Synthesis of SnO₂@ZnIn₂S₄ Composites for Highly Efficient Photocatalytic Hydrogen Evolution

by Yu-Cheng Chang, Jia-Ning Bi, Kuan-Yin Pan and Yung-Chang Chiao

Materials 2024, 17(10), 2367; https://doi.org/10.3390/ma17102367 - 15 May 2024

Cited by 3 | Viewed by 992

Abstract

This research successfully synthesized SnO₂@ZnIn₂S₄ composites for photocatalytic tap water splitting using a rapid two-step microwave-assisted synthesis method. This study investigated the impact of incorporating a fixed quantity of SnO₂ nanoparticles and combining them with various materials [...] Read more.

This research successfully synthesized SnO₂@ZnIn₂S₄ composites for photocatalytic tap water splitting using a rapid two-step microwave-assisted synthesis method. This study investigated the impact of incorporating a fixed quantity of SnO₂ nanoparticles and combining them with various materials to form composites, aiming to enhance photocatalytic hydrogen production. Additionally, different weights of SnO₂ nanoparticles were added to the ZnIn₂S₄ reaction precursor to prepare SnO₂@ZnIn₂S₄ composites for photocatalytic hydrogen production. Notably, the photocatalytic efficiency of SnO₂@ZnIn₂S₄ composites is substantially higher than that of pure SnO₂ nanoparticles and ZnIn₂S₄ nanosheets: 17.9-fold and 6.3-fold, respectively. The enhancement is credited to the successful use of visible light and the facilitation of electron transfer across the heterojunction, leading to the efficient dissociation of electron–hole pairs. Additionally, evaluations of recyclability demonstrated the remarkable longevity of SnO₂@ZnIn₂S₄ composites, maintaining high levels of photocatalytic hydrogen production over eight cycles without significant efficiency loss, indicating their impressive durability. This investigation presents a promising strategy for crafting and producing environmentally sustainable SnO₂@ZnIn₂S₄ composites with prospective implementations in photocatalytic hydrogen generation. Full article

(This article belongs to the Special Issue Nanocomposite Based Materials for Various Applications)

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28 pages, 10078 KiB

Open AccessEditor’s ChoiceReview

Dry Electrode Processing Technology and Binders

by Kaiqi Zhang, Dan Li, Xuehan Wang, Jingwan Gao, Huilin Shen, Hao Zhang, Changru Rong and Zheng Chen

Materials 2024, 17(10), 2349; https://doi.org/10.3390/ma17102349 - 15 May 2024

Cited by 4 | Viewed by 5250

Abstract

As a popular energy storage equipment, lithium-ion batteries (LIBs) have many advantages, such as high energy density and long cycle life. At this stage, with the increasing demand for energy storage materials, the industrialization of batteries is facing new challenges such as enhancing [...] Read more.

As a popular energy storage equipment, lithium-ion batteries (LIBs) have many advantages, such as high energy density and long cycle life. At this stage, with the increasing demand for energy storage materials, the industrialization of batteries is facing new challenges such as enhancing efficiency, reducing energy consumption, and improving battery performance. In particular, the challenges mentioned above are particularly critical in advanced next-generation battery manufacturing. For batteries, the electrode processing process plays a crucial role in advancing lithium-ion battery technology and has a significant impact on battery energy density, manufacturing cost, and yield. Dry electrode technology is an emerging technology that has attracted extensive attention from both academia and the manufacturing industry due to its unique advantages and compatibility. This paper provides a detailed introduction to the development status and application examples of various dry electrode technologies. It discusses the latest advancements in commonly used binders for different dry processes and offers insights into future electrode manufacturing. Full article

(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Energy Materials)

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11 pages, 7444 KiB

Open AccessEditor’s ChoiceArticle

Zinc Oxide Nanostructure Deposition into Sub-5 nm Vertical Mesopores in Silica Hard Templates by Atomic Layer Deposition

by Tauqir Nasir, Yisong Han, Chris Blackman, Richard Beanland and Andrew L. Hector

Materials 2024, 17(10), 2272; https://doi.org/10.3390/ma17102272 - 11 May 2024

Viewed by 801

Abstract

Nanostructures synthesised by hard-templating assisted methods are advantageous as they retain the size and morphology of the host templates which are vital characteristics for their intended applications. A number of techniques have been employed to deposit materials inside porous templates, such as electrodeposition, [...] Read more.

Nanostructures synthesised by hard-templating assisted methods are advantageous as they retain the size and morphology of the host templates which are vital characteristics for their intended applications. A number of techniques have been employed to deposit materials inside porous templates, such as electrodeposition, vapour deposition, lithography, melt and solution filling, but most of these efforts have been applied with pore sizes higher in the mesoporous regime or even larger. Here, we explore atomic layer deposition (ALD) as a method for nanostructure deposition into mesoporous hard templates consisting of mesoporous silica films with sub-5 nm pore diameters. The zinc oxide deposited into the films was characterised by small-angle X-ray scattering, X-ray diffraction and energy-dispersive X-ray analysis. Full article

(This article belongs to the Special Issue Atomic Layer Deposition: From Thin Films to Nanostructured Materials)

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17 pages, 6703 KiB

Open AccessEditor’s ChoiceArticle

Additively Manufactured Bionic Corrugated Lightweight Honeycomb Structures with Controlled Deformation Load-Bearing Properties

by Jie Li, Han Wang, Xianghao Kong, Zhiwei Jiao and Weimin Yang

Materials 2024, 17(10), 2274; https://doi.org/10.3390/ma17102274 - 11 May 2024

Cited by 1 | Viewed by 1053

Abstract

The rapid development of additive manufacturing (AM) has facilitated the creation of bionic lightweight, energy-absorbing structures, enabling the implementation of more sophisticated internal structural designs. For protective structures, the utilization of artificially controlled deformation patterns can effectively reduce uncertainties arising from random structural [...] Read more.

The rapid development of additive manufacturing (AM) has facilitated the creation of bionic lightweight, energy-absorbing structures, enabling the implementation of more sophisticated internal structural designs. For protective structures, the utilization of artificially controlled deformation patterns can effectively reduce uncertainties arising from random structural damage and enhance deformation stability. This paper proposed a bionic corrugated lightweight honeycomb structure with controllable deformation. The force on the onset state of deformation of the overall structure was investigated, and the possibility of controlled deformation in the homogeneous structure was compared with that in the corrugated structure. The corrugated structures exhibited a second load-bearing capacity wave peak, with the load-bearing capacity reaching 60.7% to 117.29% of the first load-bearing peak. The damage morphology of the corrugated structure still maintained relative integrity. In terms of energy absorption capacity, the corrugated lightweight structure has a much stronger energy absorption capacity than the homogeneous structure due to the second peak of the load carrying capacity. The findings of this study suggested that the combination of geometric customization and longitudinal corrugation through additive manufacturing offers a promising approach for the development of high-performance energy-absorbing structures. Full article

(This article belongs to the Section Materials Simulation and Design)

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12 pages, 17572 KiB

Open AccessEditor’s ChoiceArticle

Inductive Heating of Ceramic Matrix Composites (CMC) for High-Temperature Applications

by Alexander Hackert, Jonas H. M. Stiller, Johannes Winhard, Václav Kotlan and Daisy Nestler

Materials 2024, 17(10), 2175; https://doi.org/10.3390/ma17102175 - 7 May 2024

Viewed by 1141

Abstract

The inductive heating of a CMC susceptor for industrial applications can generate very high process temperatures. Thus, the behavior of a silicon carbide-based matrix with carbon-fiber-reinforced carbon (C/C-SiC) as a susceptor is investigated. Specifically, the influence of fiber length and the distribution of [...] Read more.

The inductive heating of a CMC susceptor for industrial applications can generate very high process temperatures. Thus, the behavior of a silicon carbide-based matrix with carbon-fiber-reinforced carbon (C/C-SiC) as a susceptor is investigated. Specifically, the influence of fiber length and the distribution of carbon fibers in the composite were investigated to find out the best parameters for the most efficient heating. For a multi-factorial set of requirements with a combination of filling levels and fiber lengths, a theoretical correlation of the material structure can be used as part of a digital model. Multi-physical simulation was performed to study the behavior of an alternating magnetic field generated by an inducing coil. The simulation results were verified by practical tests. It is shown that the inductive heating of a C/C-SiC susceptor can reach very high temperatures in a particularly fast and efficient way without oxidizing if it is ensured that a silicon carbide-based matrix completely encloses the fibers. Full article

(This article belongs to the Special Issue Damage, Fracture and Fatigue of Ceramic Matrix Composites (CMCs))

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34 pages, 28537 KiB

Open AccessEditor’s ChoiceArticle

Enhancing Quality Control: Image-Based Quantification of Carbides and Defect Remediation in Binder Jetting Additive Manufacturing

by Amit Choudhari, James Elder, Manoj Mugale, Sanoj Karki, Satyavan Digole, Stephen Omeike and Tushar Borkar

Materials 2024, 17(10), 2174; https://doi.org/10.3390/ma17102174 - 7 May 2024

Cited by 2 | Viewed by 1139

Abstract

While binder jetting (BJ) additive manufacturing (AM) holds considerable promise for industrial applications, defects often compromise part quality. This study addresses these challenges by investigating binding mechanisms and analyzing common defects, proposing tailored solutions to mitigate them. Emphasizing defect identification for effective quality [...] Read more.

While binder jetting (BJ) additive manufacturing (AM) holds considerable promise for industrial applications, defects often compromise part quality. This study addresses these challenges by investigating binding mechanisms and analyzing common defects, proposing tailored solutions to mitigate them. Emphasizing defect identification for effective quality control in BJ-AM, this research offers strategies for in-process rectification and post-process evaluation to elevate part quality. It shows how to successfully process metallic parts with complex geometries while maintaining consistent material properties. Furthermore, the paper explores the microstructure of AISI M2 tool steel, utilizing advanced image processing techniques like digital image analysis and SEM images to evaluate carbide distribution. The results show that M2 tool steel has a high proportion of M₆C carbides, with furnace-cooled samples ranging from ~2.4% to 7.1% and MC carbides from ~0.4% to 9.4%. M₆C carbides ranged from ~2.6% to 3.8% in air-cooled samples, while water-cooled samples peaked at ~8.52%. Sintering conditions also affected shrinkage, with furnace-cooled samples showing the lowest rates (1.7 ± 0.4% to 5 ± 0.4%) and water-cooled samples showing the highest (2 ± 0.4% to 14.1 ± 0.4%). The study recommends real-time defect detection systems with autonomous corrective capabilities to improve the quality and performance of BJ-AM components. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing (Volume II))

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57 pages, 14719 KiB

Open AccessEditor’s ChoiceReview

Design, Manufacturing, and Analysis of Periodic Three-Dimensional Cellular Materials for Energy Absorption Applications: A Critical Review

by Autumn R. Bernard and Mostafa S. A. ElSayed

Materials 2024, 17(10), 2181; https://doi.org/10.3390/ma17102181 - 7 May 2024

Cited by 2 | Viewed by 1243

Abstract

Cellular materials offer industries the ability to close gaps in the material selection design space with properties not otherwise achievable by bulk, monolithic counterparts. Their superior specific strength, stiffness, and energy absorption, as well as their multi-functionality, makes them desirable for a wide [...] Read more.

Cellular materials offer industries the ability to close gaps in the material selection design space with properties not otherwise achievable by bulk, monolithic counterparts. Their superior specific strength, stiffness, and energy absorption, as well as their multi-functionality, makes them desirable for a wide range of applications. The objective of this paper is to compile and present a review of the open literature focusing on the energy absorption of periodic three-dimensional cellular materials. The review begins with the methodical cataloging of qualitative and quantitative elements from 100 papers in the available literature and then provides readers with a thorough overview of the state of this research field, discussing areas such as parent material(s), manufacturing methods, cell topologies, cross-section shapes for truss topologies, analysis methods, loading types, and test strain rates. Based on these collected data, areas of great and limited research are identified and future avenues of interest are suggested for the continued maturation and growth of this field, such as the development of a consistent naming and classification system for topologies; the creation of test standards considering additive manufacturing processes; further investigation of non-uniform and non-cylindrical struts on the performance of truss lattices; and further investigation into the performance of lattice materials under the impact of non-flat surfaces and projectiles. Finally, the numerical energy absorption (by mass and by volume) data of 76 papers are presented across multiple property selection charts, highlighting various materials, manufacturing methods, and topology groups. While there are noticeable differences at certain densities, the graphs show that the categorical differences within those groups have large overlap in terms of energy absorption performance and can be referenced to identify areas for further investigation and to help in the preliminary design process by researchers and industry professionals alike. Full article

(This article belongs to the Special Issue Mechanical Behavior and Numerical Simulation of Sandwich Composites)

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10 pages, 4753 KiB

Open AccessEditor’s ChoiceArticle

Stress Distribution within the Peri-Implant Bone for Different Implant Materials Obtained by Digital Image Correlation

by Ragai Edward Matta, Lara Berger, Moritz Loehlein, Linus Leven, Juergen Taxis, Manfred Wichmann and Constantin Motel

Materials 2024, 17(9), 2161; https://doi.org/10.3390/ma17092161 - 6 May 2024

Cited by 1 | Viewed by 1237

Abstract

Stress distribution and its magnitude during loading heavily influence the osseointegration of dental implants. Currently, no high-resolution, three-dimensional method of directly measuring these biomechanical processes in the peri-implant bone is available. The aim of this study was to measure the influence of different [...] Read more.

Stress distribution and its magnitude during loading heavily influence the osseointegration of dental implants. Currently, no high-resolution, three-dimensional method of directly measuring these biomechanical processes in the peri-implant bone is available. The aim of this study was to measure the influence of different implant materials on stress distribution in the peri-implant bone. Using the three-dimensional ARAMIS camera system, surface strain in the peri-implant bone area was compared under simulated masticatory forces of 300 N in axial and non-axial directions for titanium implants and zirconia implants. The investigated titanium implants led to a more homogeneous stress distribution than the investigated zirconia implants. Non-axial forces led to greater surface strain on the peri-implant bone than axial forces. Thus, the implant material, implant system, and direction of force could have a significant influence on biomechanical processes and osseointegration within the peri-implant bone. Full article

(This article belongs to the Special Issue Advanced Dental Materials: From Design to Application)

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9 pages, 3850 KiB

Open AccessEditor’s ChoiceArticle

Molybdenum-Doped ZnO Thin Films Obtained by Spray Pyrolysis

by Pavlina Bancheva-Koleva, Veselin Zhelev, Plamen Petkov and Tamara Petkova

Materials 2024, 17(9), 2164; https://doi.org/10.3390/ma17092164 - 6 May 2024

Cited by 2 | Viewed by 1221

Abstract

A batch of ZnO thin films, pure and doped with molybdenum (up to 2 mol %), were prepared using the spray pyrolysis technique on glass and silicon substrates. The effect of molybdenum concentration on the morphology, structure and optical properties of the films [...] Read more.

A batch of ZnO thin films, pure and doped with molybdenum (up to 2 mol %), were prepared using the spray pyrolysis technique on glass and silicon substrates. The effect of molybdenum concentration on the morphology, structure and optical properties of the films was investigated. X-ray diffraction (XRD) results show a wurtzite polycrystalline crystal structure. The average crystallite size increases from 30 to 80 nm with increasing molybdenum content. Scanning electron microscopy (SEM) images demonstrate a smooth and homogeneous surface with densely spaced nanocrystalline grains. The number of nuclei increases, growing over the entire surface of the substrate with uniform grains, when the molybdenum concentration is increased to 2 mol %. The estimated root mean square (RMS) roughness values for the undoped and doped with 1 mol % and 2 mol % of ZnO thin films, defined by atomic force microscopy (AFM), are 6.12, 23.54 and 23.83 nm, respectively. The increase in Mo concentration contributes to the increase in film transmittance. Full article

(This article belongs to the Section Thin Films and Interfaces)

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25 pages, 4500 KiB

Open AccessEditor’s ChoiceArticle

In Vivo Investigation of 3D-Printed Calcium Magnesium Phosphate Wedges in Partial Load Defects

by Elke Hemmerlein, Elke Vorndran, Anna-Maria Schmitt, Franziska Feichtner, Anja-Christina Waselau and Andrea Meyer-Lindenberg

Materials 2024, 17(9), 2136; https://doi.org/10.3390/ma17092136 - 2 May 2024

Viewed by 1172

Abstract

Bone substitutes are ideally biocompatible, osteoconductive, degradable and defect-specific and provide mechanical stability. Magnesium phosphate cements (MPCs) offer high initial stability and faster degradation compared to the well-researched calcium phosphate cements (CPCs). Calcium magnesium phosphate cements (CMPCs) should combine the properties of both [...] Read more.

Bone substitutes are ideally biocompatible, osteoconductive, degradable and defect-specific and provide mechanical stability. Magnesium phosphate cements (MPCs) offer high initial stability and faster degradation compared to the well-researched calcium phosphate cements (CPCs). Calcium magnesium phosphate cements (CMPCs) should combine the properties of both and have so far shown promising results. The present study aimed to investigate and compare the degradation and osseointegration behavior of 3D powder-printed wedges of CMPC and MPC in vivo. The wedges were post-treated with phosphoric acid (CMPC) and diammonium hydrogen phosphate (MPC) and implanted in a partially loaded defect model in the proximal rabbit tibia. The evaluation included clinical, in vivo µ-CT and X-ray examinations, histology, energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) for up to 30 weeks. SEM analysis revealed a zone of unreacted material in the MPC, indicating the need to optimize the manufacturing and post-treatment process. However, all materials showed excellent biocompatibility and mechanical stability. After 24 weeks, they were almost completely degraded. The slower degradation rate of the CMPC corresponded more favorably to the bone growth rate compared to the MPC. Due to the promising results of the CMPC in this study, it should be further investigated, for example in defect models with higher load. Full article

(This article belongs to the Special Issue Bone Tissue Engineering Materials: From Preparation to Properties)

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