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Materials, Volume 16, Issue 4 (February-2 2023) – 431 articles

Cover Story (view full-size image): Nanoparticles (NPs) attract much attention due to their unique properties such as high surface area, enhanced adsorption, and catalytic and antimicrobial properties. Usually, NPs are prepared via solvent-based methods, which require solvents, often toxic, making them less attractive in terms of green chemistry. Mechanochemistry is one of the ecofriendly alternatives to the conventional synthesis of NPs, which involves mixing of reactants without or with a very small volume of solvents, gives large-surface area NPs, and facilitates their functionalization—features highly beneficial for antimicrobial applications. This review emphasizes the comparison between solvent-based and mechanochemical methods for the synthesis of mainly inorganic NPs for antimicrobial applications. View this paper
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24 pages, 21486 KiB  
Article
Characterization of Ruddlesden-Popper La2−xBaxNiO4±δ Nickelates as Potential Electrocatalysts for Solid Oxide Cells
by Kiryl Zakharchuk, Andrei Kovalevsky and Aleksey Yaremchenko
Materials 2023, 16(4), 1755; https://doi.org/10.3390/ma16041755 - 20 Feb 2023
Cited by 6 | Viewed by 2101
Abstract
Ruddlesden-Popper La2−xBaxNiO4±δ (x = 0–1.1) nickelates were prepared by a glycine-nitrate combustion route combined with high-temperature processing and evaluated for potential application as electrocatalysts for solid oxide cells and electrochemical NOx elimination. The characterization included [...] Read more.
Ruddlesden-Popper La2−xBaxNiO4±δ (x = 0–1.1) nickelates were prepared by a glycine-nitrate combustion route combined with high-temperature processing and evaluated for potential application as electrocatalysts for solid oxide cells and electrochemical NOx elimination. The characterization included structural, microstructural and dilatometric studies, determination of oxygen nonstoichiometry, measurements of electrical conductivity and oxygen permeability, and assessment of chemical compatibility with other materials. The formation range of phase-pure solid solutions was found to be limited to x = 0.5. Exceeding this limit leads to the co-existence of the main nickelate phase with low-melting Ba- and Ni-based secondary phases responsible for a strong reactivity with Pt components in experimental cells. Acceptor-type substitution of lanthanum by barium in La2−xBaxNiO4+δ is charge-compensated by decreasing oxygen excess, from δ ≈ 0.1 for x = 0 to nearly oxygen-stoichiometric state for x = 0.5 at 800 °C in air, and generation of electron-holes (formation of Ni3+). This leads to an increase in p-type electronic conductivity (up to ~80 S/cm for highly porous La1.5Ba0.5NiO4+δ ceramics at 450–900 °C) and a decline of oxygen-ionic transport. La2−xBaxNiO4+δ (x = 0–0.5) ceramics exhibit moderate thermal expansion coefficients, 13.8–14.3 ppm/K at 25–1000 °C in air. These ceramic materials react with yttria-stabilized zirconia at 700 °C with the formation of an insulating La2Zr2O7 phase but show good chemical compatibility with BaZr0.85Y0.15O3−δ solid electrolyte. Full article
(This article belongs to the Section Materials Chemistry)
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17 pages, 9130 KiB  
Article
Effect of High-Pressure Torsion and Annealing on the Structure, Phase Composition, and Microhardness of the Ti-18Zr-15Nb (at. %) Alloy
by Dmitry Gunderov, Karina Kim, Sofia Gunderova, Anna Churakova, Yuri Lebedev, Ruslan Nafikov, Mikhail Derkach, Konstantin Lukashevich, Vadim Sheremetyev and Sergey Prokoshkin
Materials 2023, 16(4), 1754; https://doi.org/10.3390/ma16041754 - 20 Feb 2023
Cited by 4 | Viewed by 1403
Abstract
The Ti-18Zr-15Nb shape memory alloys are a new material for medical implants. The regularities of phase transformations during heating of this alloy in the coarse-grained quenched state and the nanostructured state after high-pressure torsion have been studied. The specimens in quenched state (Q) [...] Read more.
The Ti-18Zr-15Nb shape memory alloys are a new material for medical implants. The regularities of phase transformations during heating of this alloy in the coarse-grained quenched state and the nanostructured state after high-pressure torsion have been studied. The specimens in quenched state (Q) and HPT state were annealed at 300–550 °C for 0.5, 3, and 12 h. The α-phase formation in Ti-18Zr-15Nb alloy occurs by C-shaped kinetics with a pronounced peak near 400–450 °C for Q state and near 350–450 °C for HPT state, and stops or slows down at higher and lower annealing temperatures. The formation of a nanostructured state in the Ti-18Zr-15Nb alloy as a result of HPT suppresses the β→ω phase transformation during low-temperature annealing (300–350 °C), but activates the β→α phase transformation. In the Q-state the α-phase during annealing at 450–500 °C is formed in the form of plates with a length of tens of microns. The α-phase formed during annealing of nanostructured specimens has the appearance of nanosized particle-grains of predominantly equiaxed shape, distributed between the nanograins of β-phase. The changes in microhardness during annealing of Q-specimens correlate with changes in phase composition during aging. Full article
(This article belongs to the Special Issue Design and Applications of Functional Materials, Volume II)
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23 pages, 3571 KiB  
Article
Parametric Analysis of Thick FGM Plates Based on 3D Thermo-Elasticity Theory: A Proper Generalized Decomposition Approach
by Mohammad-Javad Kazemzadeh-Parsi, Amine Ammar and Francisco Chinesta
Materials 2023, 16(4), 1753; https://doi.org/10.3390/ma16041753 - 20 Feb 2023
Cited by 2 | Viewed by 1523
Abstract
In the present work, the general and well-known model reduction technique, PGD (Proper Generalized Decomposition), is used for parametric analysis of thermo-elasticity of FGMs (Functionally Graded Materials). The FGMs have important applications in space technologies, especially when a part undergoes an extreme thermal [...] Read more.
In the present work, the general and well-known model reduction technique, PGD (Proper Generalized Decomposition), is used for parametric analysis of thermo-elasticity of FGMs (Functionally Graded Materials). The FGMs have important applications in space technologies, especially when a part undergoes an extreme thermal environment. In the present work, material gradation is considered in one, two and three directions, and 3D heat transfer and theory of elasticity equations are solved to have an accurate temperature field and be able to consider all shear deformations. A parametric analysis of FGM materials is especially useful in material design and optimization. In the PGD technique, the field variables are separated to a set of univariate functions, and the high-dimensional governing equations reduce to a set of one-dimensional problems. Due to the curse of dimensionality, solving a high-dimensional parametric problem is considerably more computationally intensive than solving a set of one-dimensional problems. Therefore, the PGD makes it possible to handle high-dimensional problems efficiently. In the present work, some sample examples in 4D and 5D computational spaces are solved, and the results are presented. Full article
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17 pages, 8275 KiB  
Article
Effect of Walnut-Shell Additive on the Structure and Characteristics of Concrete
by Alexey N. Beskopylny, Sergey A. Stel’makh, Evgenii M. Shcherban’, Levon R. Mailyan, Besarion Meskhi, Alexandr A. Shilov, Andrei Chernil’nik and Diana El’shaeva
Materials 2023, 16(4), 1752; https://doi.org/10.3390/ma16041752 - 20 Feb 2023
Cited by 6 | Viewed by 2228
Abstract
The partial replacement of the mineral components of concrete with natural renewable analogues in full possession of the performance characteristics of the final material, allows not only the concrete-production process to be made more environmentally friendly and inexpensive, but also to solve an [...] Read more.
The partial replacement of the mineral components of concrete with natural renewable analogues in full possession of the performance characteristics of the final material, allows not only the concrete-production process to be made more environmentally friendly and inexpensive, but also to solve an important task for the agricultural industry, which is that associated with waste disposal. The scientific novelty of the work is in the obtaining of new concrete compositions by the partial replacement of coarse aggregate with a natural analogue in the form of a walnut shell, which has the maximum ratio of the strength of the composite to its density, as well as in identifying new dependencies of strength and density and their ratio on the amount of replacement of mineral coarse-aggregate walnut shell. The main goal of this article was to analyze the effect of composition factors on characteristics of concrete with partial replacement of large aggregates with walnut shells and to search for the optimal compound that would make it possible to obtain concrete with a minimum decrease in strength characteristics with a maximum decrease in concrete density. Cubes and prism laboratory samples were made from concrete of normal density with the replacement of coarse aggregate by 5, 10, 15, 20, 25 and 30%, by volume. The main mechanical properties, such as density, strength (compressive, tensile, tensile strength in bending) of the concrete samples were studied. The investigation used standard methods and scanning electron microscopy. An increase into strength characteristics up to 3.5%, as well as the maximum ratio of strength to density of concrete, was observed at a walnut-shell dosage of 5%. Effective partial replacement of coarse aggregate with walnut shells leads to a reduction in the consumption of crushed stone by up to 10% and a decrease in the mass of concrete by up to 6%. Full article
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21 pages, 6168 KiB  
Article
A Compact Mu-Near-Zero Metamaterial Integrated Wideband High-Gain MIMO Antenna for 5G New Radio Applications
by Md. Mhedi Hasan, Mohammad Tariqul Islam, Sharul Kamal Abdul Rahim, Touhidul Alam, Hatem Rmili, Ahmed Alzamil, Md. Shabiul Islam and Mohamed S. Soliman
Materials 2023, 16(4), 1751; https://doi.org/10.3390/ma16041751 - 20 Feb 2023
Cited by 3 | Viewed by 2042
Abstract
This article demonstrates a compact wideband four-port multiple-input-multiple-output (MIMO) antenna system integrated with a wideband metamaterial (MM) to reach high gain for sub-6 GHz new radio (NR) 5G communication. The four antennas of the proposed MIMO system are orthogonally positioned to the adjacent [...] Read more.
This article demonstrates a compact wideband four-port multiple-input-multiple-output (MIMO) antenna system integrated with a wideband metamaterial (MM) to reach high gain for sub-6 GHz new radio (NR) 5G communication. The four antennas of the proposed MIMO system are orthogonally positioned to the adjacent antennas with a short interelement edge-to-edge distance (0.19λmin at 3.25 GHz), confirming compact size and wideband characteristics 55.2% (3.25–5.6 GHz). Each MIMO system component consists of a fractal slotted unique patch with a transmission feed line and a metal post-encased defected ground structure (DGS). The designed MIMO system is realized on a low-cost FR-4 printed material with a miniature size of 0.65λmin × 0.65λmin × 0.02λmin. A 6 × 6 array of double U-shaped resonator-based unique mu-near-zero (MNZ) wideband metamaterial reflector (MMR) is employed below the MIMO antenna with a 0.14λmin air gap, improving the gain by 2.8 dBi and manipulating the MIMO beam direction by 60°. The designed petite MIMO system with a MM reflector proposes a high peak gain of 7.1 dBi in comparison to recent relevant antennas with high isolation of 35 dB in the n77/n78/n79 bands. In addition, the proposed wideband MMR improves the MIMO diversity and radiation characteristics with an average total efficiency of 68% over the desired bands. The stated MIMO antenna system has an outstanding envelope correlation coefficient (ECC) of <0.045, a greater diversity gain (DG) of near 10 dB (>9.96 dB), a low channel capacity loss (CCL) of <0.35 b/s/Hz and excellent multiplexing efficiency (ME) of higher than −1.4 dB. The proposed MIMO concept is confirmed by fabricating and testing the developed MIMO structure. In contrast to the recent relevant works, the proposed antenna is compact in size, while maintaining high gain and wideband characteristics, with strong MIMO performance. Thus, the proposed concept could be a potential approach to the 5G MIMO antenna system. Full article
(This article belongs to the Section Advanced Composites)
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17 pages, 6528 KiB  
Article
New Damage Accumulation Model for Spall Propagation Mechanism in Bearing Raceways
by Ravit Ohana, Renata Klein, Roni Shneck and Jacob Bortman
Materials 2023, 16(4), 1750; https://doi.org/10.3390/ma16041750 - 20 Feb 2023
Cited by 1 | Viewed by 1378
Abstract
The aim of this study was to investigate the spall propagation mechanism in ball bearing raceways using physics-based models. Spalling is one of the most common types of bearing failures that can lead to catastrophic failure. This research takes a step forward toward [...] Read more.
The aim of this study was to investigate the spall propagation mechanism in ball bearing raceways using physics-based models. Spalling is one of the most common types of bearing failures that can lead to catastrophic failure. This research takes a step forward toward developing a prognostic tool for ball bearings. It is first necessary to understand the spall progression process in order to formulate a constitutive law of spall deterioration and to estimate the amount of remaining useful life. Fragment formation in the vicinity of the spall edge was found to consist of surface and sub-surface cracks that eventually coalesce, and a fragment is released from the raceway, based on naturally-developed spalls. Here, we describe a physics-based model, integrating a dynamic model with a finite element one to simulate this process. A continuum damage mechanics (CDM) approach and fracture mechanics tools were embedded into the finite element model to simulate the damage propagation. The formation of cracks in the vicinity of the spall (surface and sub-surface cracks) were studied using this effective stress CDM model, and the propagation of the cracks was examined using two approaches: a fracture mechanics approach and an accumulated inelastic hysteresis energy CDM approach. The latter also predicts the overall process of a single fragment release. The simulation results of the spall propagation models are supported by experimental results of spalls from both laboratory experimental bearings and an in-service Sikorsky CH-53 helicopter swashplate bearing. The results obtained show that the impact of the ball on the spall edge affects the crack propagation and the appearance of the surface and sub-surface cracks. Both release the residual stresses and cause crack propagation until a fragment is released. Full article
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10 pages, 6298 KiB  
Article
Synthesis and Characterization of Electrospun Carbon Nanofibers from Polyacrylonitrile and Graphite Nanoplatelets
by Hani Manssor Albetran
Materials 2023, 16(4), 1749; https://doi.org/10.3390/ma16041749 - 20 Feb 2023
Viewed by 1301
Abstract
Sol-gel electrospinning process was used to prepare electrospun carbon nanofibers (ECNFs) from polyacrylonitrile and graphite nanoplatelets. The nanofibers of as-electrospun carbon were calcinated in argon from room temperature to 500 °C for 1h. Scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy and [...] Read more.
Sol-gel electrospinning process was used to prepare electrospun carbon nanofibers (ECNFs) from polyacrylonitrile and graphite nanoplatelets. The nanofibers of as-electrospun carbon were calcinated in argon from room temperature to 500 °C for 1h. Scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffractometry (XRD) were used to characterize the synthesized ECNFs. The smooth ECNFs with a diameter of 129 ± 43 nm comprised conical platelets of 30–200 µm length. The plane-layered nanofibers contained crystallites along the long fiber axis and were mainly parallel. Full article
(This article belongs to the Special Issue Polymers, Multifunctional Nanomaterials, and Composites)
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34 pages, 5562 KiB  
Article
Optimisation of Mix Proportion of 3D Printable Mortar Based on Rheological Properties and Material Strength Using Factorial Design of Experiment
by Sandipan Kaushik, Mohammed Sonebi, Giuseppina Amato, Utpal Kumar Das and Arnaud Perrot
Materials 2023, 16(4), 1748; https://doi.org/10.3390/ma16041748 - 20 Feb 2023
Cited by 1 | Viewed by 2101
Abstract
In the production of 3D printable mortar (3DPM), numerous efforts have been made globally to effectively utilise various cementitious materials, admixtures, and fibres. The determination of rheological and material strength properties is crucial for successful 3D concrete printing because the materials used in [...] Read more.
In the production of 3D printable mortar (3DPM), numerous efforts have been made globally to effectively utilise various cementitious materials, admixtures, and fibres. The determination of rheological and material strength properties is crucial for successful 3D concrete printing because the materials used in 3DPM must possess the unique characteristic of making mortar flowable while being strong enough to support the weight of subsequent layers in both fresh and hardened states. The complexity of the required characteristics makes it challenging to develop an optimised mix composition that satisfies both the rheological and material strength requirements, given the wide range of available admixtures, supplementary cementitious materials, and fibres. Fly ash, basalt fibre and superplasticiser when blended with cement can help to improve the overall performance of 3DPM. The objective of this research is to optimise the rheological properties and material strength of 3D printable mortars (3DPM) containing cement, fly ash, basalt fibre, and superplasticiser. This study aims to produce 3DPM with an optimised mix composition to meet the requirements of both rheological and material strength characteristics using the factorial design approach and desirability function. Different dosages of cement, fly ash, basalt fibre, and superplasticiser are chosen as the primary design parameters to develop statistical models for the responses of rheological and material strength properties at 7 and 28 days. The results expressed in terms of the measured properties are valid for mortars made with cement ranging from 550 to 650 kg/m3, fly ash from 5% to 20% (of cement), superplasticiser from 2 to 4 kg/m3, and basalt fibre from 1 to 3 kg/m3. The rheological properties are evaluated using slump flow, cone penetrometer, and cylindrical slump tests, while the mechanical strength is evaluated using a three-point bending test and compressive test. A full factorial design experiment (FoE) is used to determine the significant parameters effecting the measured properties. Prediction models are developed to express the measured properties in terms of the primary parameters. The influence of cement, fly ash, basalt fibre, and superplasticiser is analysed using polynomial regression to determine the main effects and interactions of these primary parameters on the measured properties. The results show that the regression models established by the factorial design approach are effective and can accurately predict the performance of 3DPM. Cement, fly ash, and superplasticiser dosages have significant effects on the rheological and mechanical properties of mortar, while basalt fibre is able to influence the static yield stress and flexural strength of 3DPM. The utilisation of regression models and isoresponse curves allows for the identification of significant trends and provides valuable insight into the behaviour of the material, while desirability function is useful to optimise overall performance of mix proportions to meet the desired performance objective at fresh and hardened states. Full article
(This article belongs to the Special Issue Design and Properties of 3D Printing Concrete)
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31 pages, 6362 KiB  
Review
Creep Properties and Analysis of Cross Arms’ Materials and Structures in Latticed Transmission Towers: Current Progress and Future Perspectives
by Muhammad Rizal Muhammad Asyraf, Mazlan Rafidah, Emrah Madenci, Yasin Onuralp Özkılıç, Ceyhun Aksoylu, Muhammad Rizal Razman, Zuliskandar Ramli, Sharifah Zarina Syed Zakaria and Tabrej Khan
Materials 2023, 16(4), 1747; https://doi.org/10.3390/ma16041747 - 20 Feb 2023
Cited by 9 | Viewed by 2093
Abstract
Fibre-reinforced polymer (FRP) composites have been selected as an alternative to conventional wooden timber cross arms. The advantages of FRP composites include a high strength-to-weight ratio, lightweight, ease of production, as well as optimal mechanical performance. Since a non-conductive cross arm structure is [...] Read more.
Fibre-reinforced polymer (FRP) composites have been selected as an alternative to conventional wooden timber cross arms. The advantages of FRP composites include a high strength-to-weight ratio, lightweight, ease of production, as well as optimal mechanical performance. Since a non-conductive cross arm structure is exposed to constant loading for a very long time, creep is one of the main factors that cause structural failure. In this state, the structure experiences creep deformation, which can result in serviceability problems, stress redistribution, pre-stress loss, and the failure of structural elements. These issues can be resolved by assessing the creep trends and properties of the structure, which can forecast its serviceability and long-term mechanical performance. Hence, the principles, approaches, and characteristics of creep are used to comprehend and analyse the behaviour of wood and composite cantilever structures under long-term loads. The development of appropriate creep methods and approaches to non-conductive cross arm construction is given particular attention in this literature review, including suitable mitigation strategies such as sleeve installation, the addition of bracing systems, and the inclusion of cross arm beams in the core structure. Thus, this article delivers a state-of-the-art review of creep properties, as well as an analysis of non-conductive cross arm structures using experimental approaches. Additionally, this review highlights future developments and progress in cross arm studies. Full article
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33 pages, 11407 KiB  
Review
Latest Developments to Manufacture Metal Matrix Composites and Functionally Graded Materials through AM: A State-of-the-Art Review
by Marta Ostolaza, Jon Iñaki Arrizubieta, Aitzol Lamikiz, Soraya Plaza and Naiara Ortega
Materials 2023, 16(4), 1746; https://doi.org/10.3390/ma16041746 - 20 Feb 2023
Cited by 20 | Viewed by 4308
Abstract
Multi-material structure fabrication has the potential to address some critical challenges in today’s industrial paradigm. While conventional manufacturing processes cannot deliver multi-material structures in a single operation, additive manufacturing (AM) has come up as an appealing alternative. In particular, laser-directed energy deposition (L-DED) [...] Read more.
Multi-material structure fabrication has the potential to address some critical challenges in today’s industrial paradigm. While conventional manufacturing processes cannot deliver multi-material structures in a single operation, additive manufacturing (AM) has come up as an appealing alternative. In particular, laser-directed energy deposition (L-DED) is preferred for multi-material AM. The most relevant applications envisioned for multi-material L-DED are alloy design, metal matrix composites (MMC), and functionally graded materials (FGM). Nonetheless, there are still some issues that need to be faced before multi-material L-DED is ready for industrial use. Driven by this need, in this literature review, the suitability of L-DED for multi-material component fabrication is first demonstrated. Then, the main defects associated with multi-material L-DED and current opportunities and challenges in the field are reported. In view of the industrial relevance of high-performance coatings as tools to mitigate wear, emphasis is placed on the development of MMCs and FGMs. The identified challenges include—but are not limited to—tightly controlling the composition of the multi-material powder mixture injected into the melt pool; understanding the influence of the thermal history of the process on microstructural aspects, including the interactions between constituents; and studying the in-service behaviours of MMCs and FGMs with regard to their durability and failure modes. Full article
(This article belongs to the Special Issue Advances in Metal-Based Multi-Material Additive Manufacturing)
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14 pages, 6130 KiB  
Article
Study on the Removal of Oxide Scale Formed on 300 M Steel Special-Shaped Hot Forging Surfaces during Heating at Elevated Temperature by a High-Pressure Water Descaling Process
by Fanjiao Gongye, Jie Zhou, Jie Peng, Haicheng Zhang, Shixin Peng, Shishan Li and Heping Deng
Materials 2023, 16(4), 1745; https://doi.org/10.3390/ma16041745 - 20 Feb 2023
Cited by 4 | Viewed by 1479
Abstract
Numerical simulations and experiments were utilized to study the removal of oxide scale formed on 300 M steel special-shaped hot forging surfaces during heating at elevated temperature by a high-pressure water descaling process. Specifically, the experimental setup of the special-shaped hot forging was [...] Read more.
Numerical simulations and experiments were utilized to study the removal of oxide scale formed on 300 M steel special-shaped hot forging surfaces during heating at elevated temperature by a high-pressure water descaling process. Specifically, the experimental setup of the special-shaped hot forging was designed and manufactured according to the descaling parameters and simulation results obtained from the hot rolling process. The force states of three typical hot forging surfaces impinged by high-pressure water jets were analyzed. Moreover, the mechanism of the high-pressure water descaling process was proposed based on the research results. The numerical simulations and experimental results revealed that the velocity distribution of the high-pressure water jets is relatively different in various areas of the special-shaped hot forging surfaces. Therefore, the descaling performance is synergistically influenced by the velocity of the high-pressure water jet and the shape of the special-shaped hot forging. Given a certain spray pressure, the value of impact force Fi plays a significant role in the descaling of the typical hot forging. The larger the value of Fi on the typical hot forging surface, the easier it is to remove the oxide scale, and vice versa. Accordingly, the difficulty of removing the oxide scale formed on the 300 M steel special-shaped hot forging surfaces during heating at elevated temperature by a high-pressure water descaling process is in the following order: plane surface < convex surface < concave surface. Additionally, only the inner-layer FeO of the oxide scale remained after the high-pressure water descaling process due to the appearance of FeO-Fe2SiO4 eutectic in the FeO layer. Full article
(This article belongs to the Special Issue Research on Heat Treatment of Advanced Metallic Materials)
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15 pages, 4826 KiB  
Article
Fabrication of Hybrid Electrodes by Laser-Induced Forward Transfer for the Detection of Cu2+ Ions
by Anca Florina Bonciu, Florin Andrei and Alexandra Palla-Papavlu
Materials 2023, 16(4), 1744; https://doi.org/10.3390/ma16041744 - 20 Feb 2023
Cited by 1 | Viewed by 1431
Abstract
Composites based on poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS)—graphene oxide (GO) are increasingly considered for sensing applications. In this work we aim at patterning and prototyping microscale geometries of PEDOT:PSS: GO composites for the modification of commercially available electrochemical sensors. Here, we demonstrate the laser-induced [...] Read more.
Composites based on poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS)—graphene oxide (GO) are increasingly considered for sensing applications. In this work we aim at patterning and prototyping microscale geometries of PEDOT:PSS: GO composites for the modification of commercially available electrochemical sensors. Here, we demonstrate the laser-induced forward transfer of PEDOT:PSS: GO composites, a remarkably simple procedure that allows for the fast and clean transfer of materials with high resolution for a wide range of laser fluences (450–750 mJ/cm2). We show that it is possible to transfer PEDOT:PSS: GO composites at different ratios (i.e., 25:75 %wt and 50:50 %wt) onto flexible screen-printed electrodes. Furthermore, when testing the functionality of the PEDOT:PSS: GO modified electrodes via LIFT, we could see that both the PEDOT:PSS: GO ratio as well as the addition of an intermediate release layer in the LIFT process plays an important role in the electrochemical response. In particular, the ratio of the oxidation peak current to the reduction peak current is almost twice as high for the sensor with a 50:50 %et PEDOT:PSS: GO pixel. This direct transfer methodology provides a path forward for the prototyping and production of polymer: graphene oxide composite based devices. Full article
(This article belongs to the Special Issue Applications of Carbon-Based and Hybrid Materials in Sensors)
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15 pages, 9312 KiB  
Perspective
Lightning Strike Protection: Current Challenges and Future Possibilities
by Markus Ostermann, Juergen Schodl, Peter A. Lieberzeit, Pierluigi Bilotto and Markus Valtiner
Materials 2023, 16(4), 1743; https://doi.org/10.3390/ma16041743 - 20 Feb 2023
Cited by 2 | Viewed by 2445
Abstract
An airplane is statistically struck by lightning every year. The need for lightweight aircraft to reduce the production of carbon dioxide has significantly reduced the presence of metals in favour of composites, resulting in lower lightning strike protection efficiency. In this perspective, we [...] Read more.
An airplane is statistically struck by lightning every year. The need for lightweight aircraft to reduce the production of carbon dioxide has significantly reduced the presence of metals in favour of composites, resulting in lower lightning strike protection efficiency. In this perspective, we critically review the state of technologies in lightning strike protection solutions based on carbon materials, graphene, and MXenes. Furthermore, we comment on possible future research directions in the field. Full article
(This article belongs to the Special Issue Graphene-Based Materials and Their Potential Applications)
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13 pages, 3544 KiB  
Article
Optical and Structural Properties of Composites Based on Poly(urethane) and TiO2 Nanowires
by Malvina Stroe, Teodora Burlanescu, Mirela Paraschiv, Adam Lőrinczi, Elena Matei, Romeo Ciobanu and Mihaela Baibarac
Materials 2023, 16(4), 1742; https://doi.org/10.3390/ma16041742 - 20 Feb 2023
Cited by 3 | Viewed by 1515
Abstract
This article’s objective is the synthesis of new composites based on thermoplastic polyurethane (TPU) and TiO2 nanowires (NWs) as free-standing films, highlighting their structural and optical properties. The free-standing TPU–TiO2 NW films were prepared by a wet chemical method accompanied by [...] Read more.
This article’s objective is the synthesis of new composites based on thermoplastic polyurethane (TPU) and TiO2 nanowires (NWs) as free-standing films, highlighting their structural and optical properties. The free-standing TPU–TiO2 NW films were prepared by a wet chemical method accompanied by a thermal treatment at 100 °C for 1 h, followed by air-drying for 2 h. X-ray diffraction (XRD) studies indicated that the starting commercial TiO2 NW sample contains TiO2 tetragonal anatase (A), cubic Ti0.91O (C), and orthorhombic Ti2O3 (OR), as well as monoclinic H2Ti3O7 (M). In the presence of TPU, an increase in the ratio between the intensities of the diffraction peaks at 43.4° and 48° belonging to the C and A phases of titanium dioxide, respectively, is reported. The increase in the intensity of the peak at 43.4° is explained to be a consequence of the interaction of TiO2 NWs with PTU, which occurs when the formation of suboxides takes place. The variation in the ratio of the absorbance of the IR bands peaked at 765–771 cm−1 and 3304–3315 cm−1 from 4.68 to 4.21 and 3.83 for TPU and the TPU–TiO2 NW composites, respectively, with TiO2 NW concentration equal to 2 wt.% and 17 wt.%, indicated a decrease in the higher-order aggregates of TPU with a simultaneous increase in the hydrogen bonds established between the amide groups of TPU and the oxygen atoms of TiO2 NWs. The decrease in the ratio of the intensity of the Raman lines peaked at 658 cm−1 and 635 cm−1, which were assigned to the vibrational modes Eg in TiO2 A and Eg in H2Ti3O7 (ITiO2-A/IH2Ti3O7), respectively, from 3.45 in TiO2 NWs to 0.94–0.96 in the TPU–TiO2 NW composites, which indicates that the adsorption of TPU onto TiO2 NWs involves an exchange reaction of TPU in the presence of TiO2 NWs, followed by the formation of new hydrogen bonds between the -NH- of the amide group and the oxygen atoms of TixO2x-mn, Ti2O3, and Ti0.91O. Photoluminescence (PL) studies highlighted a gradual decrease in the intensity of the TPU emission band, which is situated in the spectral range 380–650 nm, in the presence of TiO2 NW. After increasing the TiO2 NW concentration in the TPU–TiO2 NW composite mass from 0 wt.% to 2 wt.% and 17 wt.%, respectively, a change in the binding angle of the TPU onto the TiO2 NW surface from 12.6° to 32° and 45.9°, respectively, took place. Full article
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14 pages, 12624 KiB  
Article
Significance of Melt Pool Structure on the Hydrogen Embrittlement Behavior of a Selective Laser-Melted 316L Austenitic Stainless Steel
by Jie Liu, Huajie Yang, Lingxiao Meng, Di Liu, Tianqi Xu, Daokui Xu, Xiaohong Shao, Chenwei Shao, Shujun Li, Peng Zhang and Zhefeng Zhang
Materials 2023, 16(4), 1741; https://doi.org/10.3390/ma16041741 - 20 Feb 2023
Cited by 3 | Viewed by 1966
Abstract
The hydrogen embrittlement (HE) behavior of a selective laser-melted (SLM) 316L austenitic stainless steel has been investigated by hydrogen charging experiments and slow strain rate tensile tests (SSRTs) at room temperature. The results revealed that compared to the samples without H, the ultimate [...] Read more.
The hydrogen embrittlement (HE) behavior of a selective laser-melted (SLM) 316L austenitic stainless steel has been investigated by hydrogen charging experiments and slow strain rate tensile tests (SSRTs) at room temperature. The results revealed that compared to the samples without H, the ultimate tensile strength (UTS) and elongation (EL) of specimens were decreased from 572 MPa to 552 MPa and from 60% to 36%, respectively, after 4 h of electrochemical hydrogenation with a current density of 100 mA/cm2. The negative effects of hydrogen charging were more pronounced on the samples’ ductility than on their strength. A quasi in situ EBSD observation proved that there was little phase transformation in the samples but an increased density of low angle grain boundaries, after 4 h H charging. After strain was applied, the surface of the H-sample displayed many hydrogen-induced cracks along the melt pool boundaries (MPBs) showing that these MPBs were the preferred areas for the gathering and transferring of hydrogen. Full article
(This article belongs to the Special Issue Material Design and Defect Control for Metal Additive Manufacturing)
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15 pages, 7293 KiB  
Article
Electrochemical Impedance Spectroscopy (EIS) Explanation of Single Crystal Cu(100)/Cu(111) in Different Corrosion Stages
by Qihao Lin, Guoqing Chen, Shiwen Zou, Wenlong Zhou, Xuesong Fu and Shuyan Shi
Materials 2023, 16(4), 1740; https://doi.org/10.3390/ma16041740 - 20 Feb 2023
Cited by 3 | Viewed by 2248
Abstract
Copper and its alloys are used widely in marine environments, and anisotropic corrosion influences the corrosion kinetics of copper. Corrosion of copper in an electrolyte containing Cl is described as a dissolution–deposition process, which is a prolonged process. Therefore, it is laborious [...] Read more.
Copper and its alloys are used widely in marine environments, and anisotropic corrosion influences the corrosion kinetics of copper. Corrosion of copper in an electrolyte containing Cl is described as a dissolution–deposition process, which is a prolonged process. Therefore, it is laborious to clarify the corrosion anisotropy in different stages. In this paper, electrochemical impedance spectroscopy (EIS) following elapsed open circuit potential (OCP) test with 0 h (0H), 24 h (24H) and 10 days (10D) was adopted. To exclude interruptions such as grain boundary and neighbor effect, single crystal (SC) Cu(100) and Cu(111) were employed. After 10D OCP, cross-sectional slices were cut and picked up by a focused ion beam (FIB). The results showed that the deposited oxide was Cu2O and Cu(100)/Cu(111) experienced different corrosion behaviors. In general, Cu(100) showed more excellent corrosion resistance. Combined with equivalent electrical circuit (EEC) diagrams, the corrosion mechanism of Cu(100)/Cu(111) in different stages was proposed. In the initial stage, a smaller capacitive loop of Cu(111) suggested preferential adsorption of Cl on air-formed oxide film on Cu(111). Deposited oxide and exposed bare metals also played an important role in corrosion resistance. Rectangle indentations and pyramidal structures formed on Cu(100)/Cu(111), respectively. Finally, a perfect interface on Cu(100) explained the tremendous capacitive loop and higher impedance (14,274 Ω·cm2). Moreover, defects in the oxides on Cu(111) provided channels for the penetration of electrolyte, leading to a lower impedance (9423 Ω·cm2) after 10D corrosion. Full article
(This article belongs to the Special Issue Advance in Corrosion and Protection of Metals)
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10 pages, 7937 KiB  
Article
Thermo-Compression Bonding of Cu/SnAg Pillar Bumps with Electroless Palladium Immersion Gold (EPIG) Surface Finish
by So-Yeon Jun, Jung-Hwan Bang, Min-Su Kim, Deok-Gon Han, Tae-Young Lee and Sehoon Yoo
Materials 2023, 16(4), 1739; https://doi.org/10.3390/ma16041739 - 20 Feb 2023
Viewed by 1577
Abstract
Thermo-compression bonding (TCB) properties of Cu/SnAg pillar bumps on electroless palladium immersion gold (EPIG) were evaluated in this study. A test chip with Cu/SnAg pillar bumps was bonded on the surface-finished Cu pads with the TCB method. The surface roughness of the EPIG [...] Read more.
Thermo-compression bonding (TCB) properties of Cu/SnAg pillar bumps on electroless palladium immersion gold (EPIG) were evaluated in this study. A test chip with Cu/SnAg pillar bumps was bonded on the surface-finished Cu pads with the TCB method. The surface roughness of the EPIG was 82 nm, which was 1.6 times higher than that of the ENEPIG surface finish because the EPIG was so thin that it could not flatten rough bare Cu pads. From the cross-sectional SEM micrographs, the filler trapping of the TC-bonded EPIG was much higher than that of the ENEPIG sample. The high filler trapping of the EPIG sample was due to the high surface roughness of the EPIG surface finish. The contact resistance increased as the thermal cycle time increased. The increase of the contact resistance with 1500 cycles of the thermal cycle test was 26% higher for the EPIG sample than for the ENEPIG sample. Full article
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15 pages, 4711 KiB  
Article
The Influence of Titanium Oxide Nanoparticles and UV Radiation on the Electrical Properties of PEDOT:PSS-Coated Cotton Fabrics
by Fahad Alhashmi Alamer and Rawan F. Beyari
Materials 2023, 16(4), 1738; https://doi.org/10.3390/ma16041738 - 20 Feb 2023
Cited by 3 | Viewed by 1626
Abstract
With the rapid growth of electronic textiles, there is a need for highly conductive fabrics containing fewer conductive materials, allowing them to maintain flexibility, low cost and light weight. Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS), is one of the most promising conductive materials for the [...] Read more.
With the rapid growth of electronic textiles, there is a need for highly conductive fabrics containing fewer conductive materials, allowing them to maintain flexibility, low cost and light weight. Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS), is one of the most promising conductive materials for the production of conductive fabrics due to its excellent properties such as solubility, relatively high conductivity, and market availability. Moreover, its electrical conductivity can be enhanced by polar solvents or acid treatment. The aim of this work was to fabricate conductive cotton fabrics with a small fixed amount of PEDOT:PSS and to investigate how titanium dioxide (TiO2) nanoparticles affect the electrical, thermal and structural properties of PEDOT:PSS-coated cotton fabrics. The change in electrical conductivity of the nanocomposite fabric was then related to morphological analysis by scanning electron microscopy and X-ray diffraction. We found that the sheet resistance of the nanocomposite cotton fabric depends on the TiO2 concentration, with a minimum value of 2.68 Ω/□ at 2.92 wt% TiO2. The effect of UV light on the sheet resistance of the nanocomposite cotton fabric was also investigated; we found that UV irradiation leads to an increase in conductivity at an irradiation time of 10 min, after which the conductivity decreases with increasing irradiation time. In addition, the electrical behavior of the nanocomposite cotton fabric as a function of temperature was investigated. The nanocomposite fabrics exhibited metallic behavior at high-TiO2 concentrations of 40.20 wt% and metallic semiconducting behavior at low and medium concentrations of 11.33 and 28.50 wt%, respectively. Interestingly, cotton fabrics coated with nanocomposite possessed excellent washing durability even after seven steam washes. Full article
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22 pages, 8290 KiB  
Article
Effect of the Application of Sunflower Biochar and Leafy Trees Biochar on Soil Hydrological Properties of Fallow Soils and under Soybean Cultivation
by Urszula Sadowska, Tomasz Zaleski, Maciej Kuboń, Agnieszka Latawiec, Agnieszka Klimek-Kopyra, Jakub Sikora, Maciej Gliniak, Rafał Kobyłecki and Robert Zarzycki
Materials 2023, 16(4), 1737; https://doi.org/10.3390/ma16041737 - 20 Feb 2023
Cited by 3 | Viewed by 1450
Abstract
Soils enriched with biochar are recommended as a cultivation grounds, especially in case they contain significant amount of sand. However, the interactions between biochar and plants, as well as the influence of the biochar on water retention, cultivation and air properties of soils, [...] Read more.
Soils enriched with biochar are recommended as a cultivation grounds, especially in case they contain significant amount of sand. However, the interactions between biochar and plants, as well as the influence of the biochar on water retention, cultivation and air properties of soils, are still not obvious. The present study aimed to determine the impact of various biochar doses on soils used for soya cultivation, in comparison to soils maintained as black fallow soil, on their water retention and productivity, for the period of two years. Sunflower husk biochar (BC1) and biochar of leafy trees (BC2), in doses of 0, 40, 60, 80 t·ha−1, were used for field experiments. The water retention was investigated with porous boards in pressure chambers by a drying method. No differences in the hydrological properties of the soils that were differently managed (black fallow soil, crop) were observed following biochar application. Addition of BC1, in the amounts of 40, 60, and 80 t·ha−1, caused an increase in the plant available water capacity (AWC) by 15.3%, 18.7%, and 13.3%, respectively, whereas the field capacity (FC) increased by 7.4%, 9.4%, and 8.6% for soils without biochar. Application of BC2 analogously resulted in higher AWC, by 8.97, 17.2%, and 33.1%, respectively, and higher FC by 3.75, 7.5%, and 18.3%, respectively. Increasing the doses of BC1 and BC2, both on black fallow soils and soils enriched with soya, caused a rise in total porosity (TP) and drainage porosity (DP), and a decrease in soil bulk density (SBD). Biochar with a higher total area and higher porosity (BC1) applied to soils with soya cultivation resulted in lower reductions in AW and FC than BC2 in the second year of investigation. Full article
(This article belongs to the Special Issue Biochar and Carbon-Based Materials: Properties and Applications)
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8 pages, 2314 KiB  
Article
Spin Reorientation Transition and Negative Magnetoresistance in Ferromagnetic NdCrSb3 Single Crystals
by Lei Chen, Weiyao Zhao, Zhaocai Wang, Fang Tang, Yong Fang, Zhuo Zeng, Zhengcai Xia, Zhenxiang Cheng, David L. Cortie, Kirrily C. Rule, Xiaolin Wang and Renkui Zheng
Materials 2023, 16(4), 1736; https://doi.org/10.3390/ma16041736 - 20 Feb 2023
Cited by 2 | Viewed by 1648
Abstract
High-quality NdCrSb3 single crystals are grown using a Sn-flux method, for electronic transport and magnetic structure study. Ferromagnetic ordering of the Nd3+ and Cr3+ magnetic sublattices are observed at different temperatures and along different crystallographic axes. Due to the Dzyaloshinskii–Moriya [...] Read more.
High-quality NdCrSb3 single crystals are grown using a Sn-flux method, for electronic transport and magnetic structure study. Ferromagnetic ordering of the Nd3+ and Cr3+ magnetic sublattices are observed at different temperatures and along different crystallographic axes. Due to the Dzyaloshinskii–Moriya interaction between the two magnetic sublattices, the Cr moments rotate from the b axis to the a axis upon cooling, resulting in a spin reorientation (SR) transition. The SR transition is reflected by the temperature-dependent magnetization curves, e.g., the Cr moments rotate from the b axis to the a axis with cooling from 20 to 9 K, leading to a decrease in the b-axis magnetization f and an increase in the a-axis magnetization. Our elastic neutron scattering along the a axis shows decreasing intensity of magnetic (300) peak upon cooling from 20 K, supporting the SR transition. Although the magnetization of two magnetic sublattices favours different crystallographic axes and shows significant anisotropy in magnetic and transport behaviours, their moments are all aligned to the field direction at sufficiently large fields (30 T). Moreover, the magnetic structure within the SR transition region is relatively fragile, which results in negative magnetoresistance by applying magnetic fields along either a or b axis. The metallic NdCrSb3 single crystal with two ferromagnetic sublattices is an ideal system to study the magnetic interactions, as well as their influences on the electronic transport properties. Full article
(This article belongs to the Special Issue Magnetic Topological Insulators)
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11 pages, 3522 KiB  
Article
GaAs Nanowire Photodetectors Based on Au Nanoparticles Modification
by Fengyuan Lin, Jinzhi Cui, Zhihong Zhang, Zhipeng Wei, Xiaobing Hou, Bingheng Meng, Yanjun Liu, Jilong Tang, Kexue Li, Lei Liao and Qun Hao
Materials 2023, 16(4), 1735; https://doi.org/10.3390/ma16041735 - 20 Feb 2023
Cited by 4 | Viewed by 1928
Abstract
A high-performance GaAs nanowire photodetector was fabricated based on the modification of Au nanoparticles (NPs). Au nanoparticles prepared by thermal evaporation were used to modify the defects on the surface of GaAs nanowires. Plasmons and Schottky barriers were also introduced on the surface [...] Read more.
A high-performance GaAs nanowire photodetector was fabricated based on the modification of Au nanoparticles (NPs). Au nanoparticles prepared by thermal evaporation were used to modify the defects on the surface of GaAs nanowires. Plasmons and Schottky barriers were also introduced on the surface of the GaAs nanowires, to enhance their light absorption and promote the separation of carriers inside the GaAs nanowires. The research results show that under the appropriate modification time, the dark current of GaAs nanowire photodetectors was reduced. In addition, photocurrent photodetectors increased from 2.39 × 10−10 A to 1.26 × 10−9 A. The responsivity of GaAs nanowire photodetectors correspondingly increased from 0.569 A∙W−1 to 3.047 A∙W−1. The reasons for the improvement of the photodetectors’ performance after modification were analyzed through the energy band theory model. This work proposes a new method to improve the performance of GaAs nanowire photodetectors. Full article
(This article belongs to the Special Issue Colloidal Quantum Dots for Nanophotonic Devices)
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21 pages, 7296 KiB  
Article
The Effect of Acanthocardia tuberculata Shell Powder as Filler on the Performance of Self-Compacting Mortar
by Ágata González-Caro, Antonio Manuel Merino-Lechuga, Enrique Fernández-Ledesma, José María Fernández-Rodríguez, José Ramón Jiménez and David Suescum-Morales
Materials 2023, 16(4), 1734; https://doi.org/10.3390/ma16041734 - 20 Feb 2023
Cited by 1 | Viewed by 1536
Abstract
In this research, the feasibility of using Acanthocardia tuberculata shell waste from the canning industry in the manufacturing of self-compacting mortar (SCM) was tested. The seashells were finely ground to be used as filler instead of the limestone filler normally used in this [...] Read more.
In this research, the feasibility of using Acanthocardia tuberculata shell waste from the canning industry in the manufacturing of self-compacting mortar (SCM) was tested. The seashells were finely ground to be used as filler instead of the limestone filler normally used in this type of SCM. First, a physicochemical and microstructural characterisation of all raw materials was carried out, including the particle size distribution of both fillers. Subsequently, the self-compactability properties in the fresh state of SCM were evaluated using a total substitution by volume of limestone filler for seashell powder, using different self-compactiblity parameters. The mineralogical phases of all the SCM tested were identified once hardened by means of X-ray diffraction technique, thermogravimetric and differential thermal analysis. In addition, the mechanical properties, water absorption capacity, dry bulk density and accessible porosity of water of hardened mortars at 28 days of curing were analysed. The effect of replacing limestone filler by Acanthocardia tuberculata filler resulted in a decrease in compressive strength of 29.43, 16.84 and 2.29%, respectively. The results indicate that it is possible to completely replace natural limestone filler with Acanthocardia tuberculata shell filler without significantly affecting the mechanical properties of SCM. Full article
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12 pages, 4295 KiB  
Article
Preparation of Micro-Size Spherical Silver Particles and Their Application in Conductive Silver Paste
by Na Li, Jun Li, Xiaoxi Wan, Yifan Niu, Yongwan Gu, Guo Chen and Shaohua Ju
Materials 2023, 16(4), 1733; https://doi.org/10.3390/ma16041733 - 20 Feb 2023
Cited by 4 | Viewed by 2339
Abstract
In this paper, micro-size spherical silver particles were prepared by using a wet-chemical reduction method. The silver particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and a laser particle-size analyzer. The results indicate that different types and the content of [...] Read more.
In this paper, micro-size spherical silver particles were prepared by using a wet-chemical reduction method. The silver particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and a laser particle-size analyzer. The results indicate that different types and the content of surfactants can be used to prevent the accumulation, and control the morphology and particle size distribution, of silver particles. Moreover, the morphology of silver particles was changed from polyhedral to spherical when the pH was raised from 1 to 3. Under the optimal synthesis conditions (0.1 mol/L silver nitrate, 0.06 mol/L ascorbic acid, gelatin (5% by weight of silver nitrate), pH = 1), the micro-size spherical silver particles with diameter of 5–8 μm were obtained. In addition, the resistivity of conductive silver paste that prepared with the as-synthesized spherical silver particles was discussed in detail and the average resistivity of the conductive silver paste was 3.57 × 10−5 Ω·cm after sintering at 140 °C for 30 min. Full article
(This article belongs to the Special Issue Recovery of Non-ferrous Metal from Metallurgical Residues)
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12 pages, 2718 KiB  
Article
Processing of Low-Density HGM-Filled Epoxy–Syntactic Foam Composites with High Specific Properties for Marine Applications
by Olusegun Adigun Afolabi, Turup Pandurangan Mohan and Krishnan Kanny
Materials 2023, 16(4), 1732; https://doi.org/10.3390/ma16041732 - 20 Feb 2023
Cited by 3 | Viewed by 1369
Abstract
A solution casting approach is used to create hollow glass microsphere (HGM)-filled epoxy–syntactic foam composites (e–SFCs) by varying the concentrations of HGM in epoxy according to different particle sizes. Density analysis is used to investigate the impact of concentration and particle size regularity [...] Read more.
A solution casting approach is used to create hollow glass microsphere (HGM)-filled epoxy–syntactic foam composites (e–SFCs) by varying the concentrations of HGM in epoxy according to different particle sizes. Density analysis is used to investigate the impact of concentration and particle size regularity on the microstructure of e-SFCs. It was observed that e–SFCs filled with an HGM of uniform particle sizes exhibit a reduction in density with increasing HGM concentration, whereas e-SFCs filled with heterogeneous sizes of HGM exhibit closeness in density values regardless of HGM concentration. The variation in e–SFC density can be related to HGM packing efficiency within e–SFCs in terms of concentration and particle size regularity. The particle size with lowest true density of 0.5529 g/cm3, experimental density of 0.949 g/cm3 and tensile strength of 55.74 MPa resulted in e-SFCs with highest specific properties of 100.81 (MPa·g/cm3), with a 35.1% increase from the lowest value of 74.64 (MPa·g/cm3) at a true density of 0.7286 g/cm3, experimental density of 0.928 g/cm3 and tensile strength of 54.38 MPa. The e–SFCs’ theoretical density values were obtained. The variance in theoretical and experimental density values provides a thorough grasp of packing efficiency and inter-particle features. Full article
(This article belongs to the Special Issue Recent Advances in Functional Polymer Nanocomposites)
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13 pages, 7725 KiB  
Article
Influence of the Hydrogen Doping Method on the Atomic Structure, Mechanical Properties and Relaxation Behaviors of Metallic Glasses
by Jiacheng Zhang, Pengfei Gao and Weixu Zhang
Materials 2023, 16(4), 1731; https://doi.org/10.3390/ma16041731 - 20 Feb 2023
Viewed by 1284
Abstract
The interaction of metallic glasses (MGs) with hydrogen can trigger many interesting physical, chemical and mechanical phenomena. However, atomic-scale understanding is still lacking. In this work, molecular dynamics (MD) simulations are employed to study the atomic structure, mechanical properties and relaxation behaviors of [...] Read more.
The interaction of metallic glasses (MGs) with hydrogen can trigger many interesting physical, chemical and mechanical phenomena. However, atomic-scale understanding is still lacking. In this work, molecular dynamics (MD) simulations are employed to study the atomic structure, mechanical properties and relaxation behaviors of H-doped Ni50Al50 MGs doped by two methods. The properties of H-doped MGs are determined not only by the hydrogen content but also by the doping method. When H atoms are doped into the molten state of samples, H atoms can fully diffuse and interact with metallic atoms, resulting in loose local atomic structures, homogeneous deformation and enhanced β relaxation. In contrast, when H atoms are doped into as-cast MGs, the H content is crucial in affecting the atomic structure and mechanical properties. A small number of H atoms has little influence on the elastic matrix, while the percolation of shear transformation zones (STZs) is hindered by H atoms, resulting in the delay of shear band (SB) formation and an insignificant change in the strength. However, a large number of H atoms can make the elastic matrix loose, leading to the decrease in strength and the transition of the deformation mode from SB to homogeneous deformation. The H effects on the elastic matrix and flow units are also applied to the dynamic relaxation. The deformability of H-doped Ni50Al50 MGs is enhanced by both H-doping methods; however, our results reveal that the mechanisms are different. Full article
(This article belongs to the Special Issue Mechanical Properties of Advanced Materials and Structures)
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10 pages, 3334 KiB  
Article
The Effect of Periodic Duty Cyclings in Metal-Modulated Epitaxy on GaN:Mg Film
by Jun Fang, Wenxian Yang, Xue Zhang, Aiqin Tian, Shulong Lu, Jianping Liu and Hui Yang
Materials 2023, 16(4), 1730; https://doi.org/10.3390/ma16041730 - 20 Feb 2023
Viewed by 1438
Abstract
Metal modulation epitaxy (MME) is a technique in which metal beams (Al, Ga, In, and Mg) are switched on and off in short periods in an RF MBE system while a continuous nitrogen plasma beam is kept on. We systematically studied the effect [...] Read more.
Metal modulation epitaxy (MME) is a technique in which metal beams (Al, Ga, In, and Mg) are switched on and off in short periods in an RF MBE system while a continuous nitrogen plasma beam is kept on. We systematically studied the effect of periodic duty cycling on the morphology, crystalline quality, Mg doping concentration, and electrical properties of GaN:Mg films grown by MME. When the metal shutter duty cycling is 20 s open/10 s close, the sample has smooth surface with clear steps even with Mg doping concentration higher than 1 × 1020 cm−3. The RMS roughness is about 0.5 nm. The FWHM of (002) XRD rocking curve is 230 arcsec and the FWHM of (102) XRD rocking curve is 260 arcsec. As result, a hole concentration of 5 × 1018 cm−3 and a resistivity of 1.5 Ω·cm have been obtained. The hole concentration increases due to the incorporation of surface accumulated Mg dopants into suitable Ga substitutional sites with minimal formation of compensatory defects. Full article
(This article belongs to the Special Issue III-V Semiconductor Optoelectronics: Materials and Devices)
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16 pages, 3141 KiB  
Article
Melt Pool Shape Evaluation by Single-Track Experiments and Finite-Element Thermal Analysis: Balling and Lack of Fusion Criteria for Generating Process Window of Inconel738LC
by Jun Katagiri, Masahiro Kusano, Satoshi Minamoto, Houichi Kitano, Koyo Daimaru, Masakazu Tsujii and Makoto Watanabe
Materials 2023, 16(4), 1729; https://doi.org/10.3390/ma16041729 - 20 Feb 2023
Cited by 3 | Viewed by 1756
Abstract
Defects occur in laser powder bed fusion (L-PBF) such as the keyholing, lack of fusion, and the balling depending on the laser power (P) and the scan speed (V). The figure shows that the occupied regions of each defect [...] Read more.
Defects occur in laser powder bed fusion (L-PBF) such as the keyholing, lack of fusion, and the balling depending on the laser power (P) and the scan speed (V). The figure shows that the occupied regions of each defect are the process window and are essentially important to fabricate a high-quality part. This paper is a study of process window generation using single-track experiments and finite-element method simulation of thermal conduction for Inconel738LC alloy. A series of single-track experiments were conducted varying the range of P and V and the results were classified into keyholing, lack of fusion, balling, and good track. A series of simulations were conducted and validated by comparison with the experiments. To quantitively identify the balling, the isolines from the contour map generated by the results of simulations and the balling criteria of the ratio of melt pool length and the depth (L/D) of 7.69 were determined considering the past theoretical studies. The lack of fusion criteria: the ratio of the overlap depth in fabrication using multi-scan (Dov) and powder layer thickness (t) of 0.1 was obtained. Using the criteria obtained from the experiments and simulation, the process window was generated. Full article
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13 pages, 2137 KiB  
Article
Stress Intensity Factor (SIF) Solutions and Fatigue Crack Paths in Eccentric Circumferentially Cracked Round Bar (CCRB) in Tension
by Jesús Toribio, Juan-Carlos Matos and Beatriz González
Materials 2023, 16(4), 1728; https://doi.org/10.3390/ma16041728 - 20 Feb 2023
Viewed by 1209
Abstract
In this paper, a numerical modeling was developed to study (on the basis of the Paris law) the fatigue propagation paths of eccentric external (outer) cracks in circumferentially cracked round bars (CCRB) subjected to a cyclic type of loading in the form of [...] Read more.
In this paper, a numerical modeling was developed to study (on the basis of the Paris law) the fatigue propagation paths of eccentric external (outer) cracks in circumferentially cracked round bars (CCRB) subjected to a cyclic type of loading in the form of either remote tensile loading or imposed axial displacement. Results show how the eccentricity (in relation to the wire axis) of the circular resistant ligament increases with the growth of outer circumferential cracks by subcritical fatigue mechanisms. This phenomenon is more pronounced when the solicitation consists of a remote tensile loading than when it is an axial displacement, when the initial eccentricity of the ligament increases (for a given initial diameter), and when the Paris exponent characteristic of the material rises. The paper also analyzes in depth the different situations regarding contact between crack faces during subcritical cyclic fatigue propagation, covering a wide range of cases including no contact, partial contact, and full contact depending on the ligament diameter (during the process of fatigue crack advance) and the relative eccentricity of the annular crack that loses its axial symmetry in relation to the round bar (cylinder) axis. In addition to the fatigue crack path study, closed-form stress intensity factor (SIF) solutions for the considered geometry (a cylinder with an outer annular crack) are provided in the form of third-degree polynomial expressions as a function of the ligament diameter and the crack eccentricity (both in dimensionless terms). Full article
(This article belongs to the Special Issue Mechanics, Fatigue and Fracture of Metallic Materials)
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2 pages, 149 KiB  
Editorial
Experimental, Theoretical, Numerical and Big-Data-Based Investigations on Characterizations for Geomaterials
by Shaofeng Wang
Materials 2023, 16(4), 1727; https://doi.org/10.3390/ma16041727 - 20 Feb 2023
Viewed by 938
Abstract
Rock and rock-like materials such as concrete, soil, and underground backfilling materials are considered to be geomaterials [...] Full article
14 pages, 3665 KiB  
Article
Changes in Abrasion Resistance of Cast Cr-Ni Steel as a Result of the Formation of Niobium Carbides in Alloy Matrix
by Grzegorz Tęcza
Materials 2023, 16(4), 1726; https://doi.org/10.3390/ma16041726 - 19 Feb 2023
Cited by 2 | Viewed by 1516
Abstract
Cast austenitic chromium-nickel steel is commonly used for the manufacture of machine parts and components, which are exposed to the attack of corrosive media and abrasive wear during operation. The most commonly used grades include GX2CrNi18-9 and X10CrNi18-8 as well as GX2CrNiMo17-12-2 and [...] Read more.
Cast austenitic chromium-nickel steel is commonly used for the manufacture of machine parts and components, which are exposed to the attack of corrosive media and abrasive wear during operation. The most commonly used grades include GX2CrNi18-9 and X10CrNi18-8 as well as GX2CrNiMo17-12-2 and X6CrNiMoNb17-12-2. To improve the abrasion resistance of cast chromium-nickel steel, primary niobium carbides were produced in the metallurgical process by increasing the carbon content and adding Fe-Nb. The microstructure of the obtained test castings consisted of an austenitic matrix and primary niobium carbides evenly distributed in this matrix. The measured hardness of the samples after heat treatment ranged from 215 to 240 HV and was higher by about 60 units than the hardness of the reference cast GX10CrNi18-9 steel, which had a hardness of about 180 HV. Compared to the reference cast steel, the abrasive wear resistance of the tested cast chromium-nickel steel (measured in Miller test) with contents of 4.4 and 5.4 wt% Nb increased only slightly, i.e., by 5% for the lower niobium content and 11% for the higher niobium content. Compared to ordinary cast GX10CrNi18-9 steel, the addition of 9.2 wt% Nb reduced the abrasive wear by almost 2.5 times. Full article
(This article belongs to the Special Issue Advances in Alloys - Microstructure, Manufacturing and Analysis)
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