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Editor’s Choice Articles

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

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17 pages, 3440 KiB  
Article
Structure, Antioxidant Activity and Antimicrobial Study of Light Lanthanide Complexes with p-Coumaric Acid
by Grzegorz Świderski, Ewelina Gołębiewska, Natalia Kowalczyk, Monika Kalinowska, Renata Świsłocka, Elżbieta Wołejko, Urszula Wydro, Piotr Malinowski, Anna Pietryczuk, Adam Cudowski, Waldemar Priebe and Włodzimierz Lewandowski
Materials 2024, 17(6), 1324; https://doi.org/10.3390/ma17061324 - 13 Mar 2024
Viewed by 483
Abstract
This paper presents the results of a study of the effects of the lanthanide ions Ce3+, Pr3+, Nd3+ and Sm3+ on the electronic structure and antioxidant and biological (antimicrobial and cytotoxic) properties of p-coumaric acid (p-CAH2 [...] Read more.
This paper presents the results of a study of the effects of the lanthanide ions Ce3+, Pr3+, Nd3+ and Sm3+ on the electronic structure and antioxidant and biological (antimicrobial and cytotoxic) properties of p-coumaric acid (p-CAH2). Structural studies were conducted via spectroscopic methods (FTIR, ATR, UV). Thermal degradation studies of the complexes were performed. The results are presented in the form of TG, DTG and DSC curves. Antioxidant properties were determined via activity tests against DPPH, ABTS and OH radicals. The reducing ability was tested via CUPRAC assays. Minimum inhibitory concentrations (MICs) of the ligand and lanthanide complexes were determined on E. coli, B. subtilis and C. albicans microorganisms. The antimicrobial activity was also determined using the MTT assay. The results were presented as the relative cell viability of C. albicans, P. aeruginosa, E. coli and S. aureus compared to controls and expressed as percentages. In the obtained complexes in the solid phase, lanthanide ions coordinate three ligands in a bidentate chelating coordination mode through the carboxyl group of the acid. Spectroscopic analysis showed that lanthanide ions increase the aromaticity of the pi electron system of the ligand. Thermal analysis showed that the complexes are hydrated and have a higher thermal stability than the ligand. The products of thermal decomposition of the complexes are lanthanide oxides. In the aqueous phase, the metal combines with the ligand in a 1:1 molar ratio. Antioxidant activity tests showed that the complexes have a similar ability to remove free radicals. ABTS and DPPH tests showed that the complexes have twice the ability to neutralise radicals than the ligand, and a much higher ability to remove the hydroxyl radical. The abilities of the complexes and the free ligand to reduce Cu2+ ions in the CUPRAC test are at a similar level. Lanthanide complexes of p-coumaric acid are characterised by a higher antimicrobial capacity than the free ligand against Escherichia coli bacteria, Bacillus subtilis and Candida albicans fungi. Full article
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20 pages, 6220 KiB  
Article
The Beneficial Impact of Mineral Content in Spent-Coffee-Ground-Derived Hard Carbon on Sodium-Ion Storage
by Sonya Harizanova, Ivan Uzunov, Lyubomir Aleksandrov, Maria Shipochka, Ivanka Spassova and Mariya Kalapsazova
Materials 2024, 17(5), 1016; https://doi.org/10.3390/ma17051016 - 22 Feb 2024
Viewed by 526
Abstract
The key technological implementation of sodium-ion batteries is converting biomass-derived hard carbons into effective anode materials. This becomes feasible if appropriate knowledge of the relations between the structure of carbonized biomass products, the mineral ash content in them, and Na storage properties is [...] Read more.
The key technological implementation of sodium-ion batteries is converting biomass-derived hard carbons into effective anode materials. This becomes feasible if appropriate knowledge of the relations between the structure of carbonized biomass products, the mineral ash content in them, and Na storage properties is gained. In this study, we examine the simultaneous impact of the ash phase composition and carbon structure on the Na storage properties of hard carbons derived from spent coffee grounds (SCGs). The carbon structure is modified using the pre-carbonization of SCGs at 750 °C, followed by annealing at 1100 °C in an Ar atmosphere. Two variants of the pre-carbonization procedure are adopted: the pre-carbonization of SCGs in a fixed bed and CO2 flow. For the sake of comparison, the pre-carbonized products are chemically treated to remove the ash content. The Na storage performance of SCG-derived carbons is examined in model two and three Na-ion cells. It was found that ash-containing carbons outperformed the ash-free analogs with respect to cycling stability, Coulombic efficiency, and rate capability. The enhanced performance is explained in terms of the modification of the carbon surface by ash phases (mainly albite) and its interaction with the electrolyte, which is monitored by ex situ XPS. Full article
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35 pages, 16769 KiB  
Review
2D Materials Nanoarchitectonics for 3D Structures/Functions
by Katsuhiko Ariga
Materials 2024, 17(4), 936; https://doi.org/10.3390/ma17040936 - 17 Feb 2024
Viewed by 1125
Abstract
It has become clear that superior material functions are derived from precisely controlled nanostructures. This has been greatly accelerated by the development of nanotechnology. The next step is to assemble materials with knowledge of their nano-level structures. This task is assigned to the [...] Read more.
It has become clear that superior material functions are derived from precisely controlled nanostructures. This has been greatly accelerated by the development of nanotechnology. The next step is to assemble materials with knowledge of their nano-level structures. This task is assigned to the post-nanotechnology concept of nanoarchitectonics. However, nanoarchitectonics, which creates intricate three-dimensional functional structures, is not always easy. Two-dimensional nanoarchitectonics based on reactions and arrangements at the surface may be an easier target to tackle. A better methodology would be to define a two-dimensional structure and then develop it into a three-dimensional structure and function. According to these backgrounds, this review paper is organized as follows. The introduction is followed by a summary of the three issues; (i) 2D to 3D dynamic structure control: liquid crystal commanded by the surface, (ii) 2D to 3D rational construction: a metal–organic framework (MOF) and a covalent organic framework (COF); (iii) 2D to 3D functional amplification: cells regulated by the surface. In addition, this review summarizes the important aspects of the ultimate three-dimensional nanoarchitectonics as a perspective. The goal of this paper is to establish an integrated concept of functional material creation by reconsidering various reported cases from the viewpoint of nanoarchitectonics, where nanoarchitectonics can be regarded as a method for everything in materials science. Full article
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12 pages, 3039 KiB  
Article
Atomic-Scale Structural Properties in NiCo2O4/CuFe2O4 Bilayer Heterostructures on (001)-MgAl2O4 Substrate Regulated by Film Thickness
by Kun Liu, Ruyi Zhang, Jiankang Li and Songyou Zhang
Materials 2024, 17(4), 871; https://doi.org/10.3390/ma17040871 - 13 Feb 2024
Viewed by 405
Abstract
Changing film thickness to manipulate microstructural properties has been considered as a potential method in practical application. Here, we report that atomic-scale structural properties are regulated by film thickness in an NiCO2O4(NCO)/CuFe2O4(CFO) bilayer heterostructure prepared [...] Read more.
Changing film thickness to manipulate microstructural properties has been considered as a potential method in practical application. Here, we report that atomic-scale structural properties are regulated by film thickness in an NiCO2O4(NCO)/CuFe2O4(CFO) bilayer heterostructure prepared on (001)-MgAl2O4 (MAO) substrate by means of aberration-corrected scanning transmission electron microscopy (STEM). The misfit dislocations at the NCO/CFO interface and antiphase boundaries (APBs) bound to dislocations within the films are both found in NCO (40 nm)/CFO (40 nm)/MAO heterostructures, contributing to the relaxation of mismatch lattice strain. In addition, the non-overlapping a/4[101]-APB is found and the structural transformation of this kind of APB is resolved at the atomic scale. In contrast, only the interfacial dislocations form at the interface without the formation of APBs within the films in NCO (10 nm)/CFO (40 nm)/MAO heterostructures. Our results provide evidence that the formation of microstructural defects can be regulated by changing film thickness to tune the magnetic properties of epitaxial bilayer spinel oxide films. Full article
(This article belongs to the Section Thin Films and Interfaces)
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13 pages, 3072 KiB  
Article
Fabrication and Characterization of an Electrochemical Platform for Formaldehyde Oxidation, Based on Glassy Carbon Modified with Multi-Walled Carbon Nanotubes and Electrochemically Generated Palladium Nanoparticles
by Andrzej Leniart, Barbara Burnat, Mariola Brycht, Maryia-Mazhena Dzemidovich and Sławomira Skrzypek
Materials 2024, 17(4), 841; https://doi.org/10.3390/ma17040841 - 09 Feb 2024
Viewed by 617
Abstract
This study outlines the fabrication process of an electrochemical platform utilizing glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and palladium nanoparticles (PdNPs). The MWCNTs were applied on the GCE surface using the drop-casting method and PdNPs were produced electrochemically by [...] Read more.
This study outlines the fabrication process of an electrochemical platform utilizing glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and palladium nanoparticles (PdNPs). The MWCNTs were applied on the GCE surface using the drop-casting method and PdNPs were produced electrochemically by a potentiostatic method employing various programmed charges from an ammonium tetrachloropalladate(II) solution. The resulting GCEs modified with MWCNTs and PdNPs underwent comprehensive characterization for topographical and morphological attributes, utilizing atomic force microscopy and scanning electron microscopy along with energy-dispersive X-ray spectrometry. Electrochemical assessment of the GCE/MWCNTs/PdNPs involved cyclic voltammetry (CV) and electrochemical impedance spectroscopy conducted in perchloric acid solution. The findings revealed even dispersion of PdNPs, and depending on the electrodeposition parameters, PdNPs were produced within four size ranges, i.e., 10–30 nm, 20–40 nm, 50–60 nm, and 70–90 nm. Additionally, the electrocatalytic activity toward formaldehyde oxidation was assessed through CV. It was observed that an increase in the size of the PdNPs corresponded to enhanced catalytic activity in the formaldehyde oxidation reaction on the GCE/MWCNTs/PdNPs. Furthermore, satisfactory long-term stability over a period of 42 days was noticed for the GCE/MWCNTs/PDNPs(100) material which demonstrated the best electrocatalytic properties in the electrooxidation reaction of formaldehyde. Full article
(This article belongs to the Special Issue Advanced Electrode Materials Dedicated for Electroanalysis)
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15 pages, 5964 KiB  
Article
Mesoporous Silica MCM-41 from Fly Ash as a Support of Bimetallic Cu/Mn Catalysts for Toluene Combustion
by Jakub Mokrzycki, Monika Fedyna, Dorota Duraczyńska, Mateusz Marzec, Rafał Panek, Wojciech Franus, Tomasz Bajda and Robert Karcz
Materials 2024, 17(3), 653; https://doi.org/10.3390/ma17030653 - 29 Jan 2024
Viewed by 593
Abstract
The main outcome of this research was to demonstrate the opportunity to obtain a stable and well-ordered structure of MCM-41 synthesized from fly ash. A series of bimetallic (Cu/Mn) catalysts supported at MCM-41 were prepared via grinding method and investigated in catalytic toluene [...] Read more.
The main outcome of this research was to demonstrate the opportunity to obtain a stable and well-ordered structure of MCM-41 synthesized from fly ash. A series of bimetallic (Cu/Mn) catalysts supported at MCM-41 were prepared via grinding method and investigated in catalytic toluene combustion reaction to show the material’s potential application. It was proved, that the Cu/Mn ratio had a crucial effect on the catalytic activity of prepared materials. The best catalytic performance was achieved with sample Cu/Mn(2.5/2.5), for which the temperature of 50% toluene conversion was found to be 300 °C. This value remains in line with the literature reports, for which comparable catalytic activity was attained for 3-fold higher metal loadings. Time-on-stream experiment proved the thermal stability of the investigated catalyst Cu/Mn(2.5/2.5). The obtained results bring a valuable background in the field of fly ash utilization, where fly ash-derived MCM-41 can be considered as efficient and stable support for dispersion of active phase for catalyst preparation. Full article
(This article belongs to the Special Issue Applications of Silica and Silica-Based Composites)
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17 pages, 8300 KiB  
Article
The Influence of the Molecular Structure of Compounds on Their Properties and the Occurrence of Chiral Smectic Phases
by Magdalena Urbańska, Monika Zając, Paweł Perkowski and Aleksandra Deptuch
Materials 2024, 17(3), 618; https://doi.org/10.3390/ma17030618 - 27 Jan 2024
Viewed by 546
Abstract
We have designed new chiral smectic mesogens with the -CH2O group near the chiral center. We synthesized two unique rod-like compounds. We determined the mesomorphic properties of these mesogens and confirmed the phase identification using dielectric spectroscopy. Depending on the length [...] Read more.
We have designed new chiral smectic mesogens with the -CH2O group near the chiral center. We synthesized two unique rod-like compounds. We determined the mesomorphic properties of these mesogens and confirmed the phase identification using dielectric spectroscopy. Depending on the length of the oligomethylene spacer (i.e., the number of methylene groups) in the achiral part of the molecules, the studied materials show different phase sequences. Moreover, the temperature ranges of the observed smectic phases are different. It can be seen that as the length of the alkyl chain increases, the liquid crystalline material shows more mesophases. Additionally, its clearing (isotropization) temperature increases. The studied compounds are compared with the structurally similar smectogens previously synthesized. The helical pitch measurements were performed using the selective reflection method. These materials can be useful and effective as chiral components and dopants in smectic mixtures targeted for optoelectronics and photonics. Full article
(This article belongs to the Special Issue Advanced Materials for Luminescent Applications)
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15 pages, 2605 KiB  
Review
Divalent Metal Ion Depletion from Wastewater by RVC Cathodes: A Critical Review
by Alessandro Dell’Era, Carla Lupi, Erwin Ciro, Francesca A. Scaramuzzo and Mauro Pasquali
Materials 2024, 17(2), 464; https://doi.org/10.3390/ma17020464 - 18 Jan 2024
Viewed by 483
Abstract
In this paper, a critical review of results obtained using a reticulated vitreous carbon (RVC) three-dimensional cathode for the electrochemical depletion of various divalent ions, such as Cu+2, Cd+2, Pb+2, Zn+2, Ni+2, and [...] Read more.
In this paper, a critical review of results obtained using a reticulated vitreous carbon (RVC) three-dimensional cathode for the electrochemical depletion of various divalent ions, such as Cu+2, Cd+2, Pb+2, Zn+2, Ni+2, and Co+2, often present in wastewater, has been carried out. By analyzing the kinetics and fluid dynamics of the process found in literature, a general dimensionless equation, Sh = f(Re), has been determined, describing a general trend for all the analyzed systems regardless of the geometry, dimensions, and starting conditions. Thus, a map in the log(Sh) vs. log(Re) plane has been reported by characterizing the whole ion electrochemical depletion process and highlighting the existence of a good correlation among all the results. Moreover, because in recent years, the interest in using this three-dimensional cathode material seems to have slowed, the intent is to revive it as a useful tool for metal recovery, recycling processes, and water treatments. Full article
(This article belongs to the Special Issue Electrochemical Material Science and Electrode Processes)
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47 pages, 7700 KiB  
Review
On the Durability of Icephobic Coatings: A Review
by Andrés Nistal, Benjamín Sierra-Martín and Antonio Fernández-Barbero
Materials 2024, 17(1), 235; https://doi.org/10.3390/ma17010235 - 31 Dec 2023
Cited by 1 | Viewed by 1655
Abstract
Ice formation and accumulation on surfaces has a negative impact in many different sectors and can even represent a potential danger. In this review, the latest advances and trends in icephobic coatings focusing on the importance of their durability are discussed, in an [...] Read more.
Ice formation and accumulation on surfaces has a negative impact in many different sectors and can even represent a potential danger. In this review, the latest advances and trends in icephobic coatings focusing on the importance of their durability are discussed, in an attempt to pave the roadmap from the lab to engineering applications. An icephobic material is expected to lower the ice adhesion strength, delay freezing time or temperature, promote the bouncing of a supercooled drop at subzero temperatures and/or reduce the ice accretion rate. To better understand what is more important for specific icing conditions, the different types of ice that can be formed in nature are summarized. Similarly, the alternative methods to evaluate the durability are reviewed, as this is key to properly selecting the method and parameters to ensure the coating is durable enough for a given application. Finally, the different types of icephobic surfaces available to date are considered, highlighting the strategies to enhance their durability, as this is the factor limiting the commercial applicability of icephobic coatings. Full article
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24 pages, 11690 KiB  
Article
Crashworthiness of Additively Manufactured Auxetic Lattices: Repeated Impacts and Penetration Resistance
by Paolo Franzosi, Ivan Colamartino, Alessandro Giustina, Marco Anghileri and Marco Boniardi
Materials 2024, 17(1), 186; https://doi.org/10.3390/ma17010186 - 29 Dec 2023
Cited by 1 | Viewed by 743
Abstract
Auxetic materials have recently attracted interest in the field of crashworthiness thanks to their peculiar negative Poisson ratio, leading to densification under compression and potentially being the basis of superior behavior upon impact with respect to conventional cellular cores or standard solutions. However, [...] Read more.
Auxetic materials have recently attracted interest in the field of crashworthiness thanks to their peculiar negative Poisson ratio, leading to densification under compression and potentially being the basis of superior behavior upon impact with respect to conventional cellular cores or standard solutions. However, the empirical demonstration of the applicability of auxeticity under impact is limited for most known geometries. As such, the present work strives to advance the investigation of the impact behavior of auxetic meta-materials: first by selecting and testing representative specimens, then by proceeding with an experimental and numerical study of repeated impact behavior and penetration resistance, and finally by proposing a new design of a metallic auxetic absorber optimized for additive manufacturing and targeted at high-performance crash applications. Full article
(This article belongs to the Special Issue Mechanical Performance of Advanced Composite Materials and Structures)
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23 pages, 5067 KiB  
Article
Green Synthesis of Silver Nanoparticles Using the Cell-Free Supernatant of Haematococcus pluvialis Culture
by Maria G. Savvidou, Evgenia Kontari, Styliani Kalantzi and Diomi Mamma
Materials 2024, 17(1), 187; https://doi.org/10.3390/ma17010187 - 29 Dec 2023
Viewed by 606
Abstract
The green synthesis of silver nanoparticles (AgNPs) using the cell-free supernatant of a Haematococcus pluvialis culture (CFS) was implemented in the current study, under illumination conditions. The reduction of Ag+ to AgNPs by the CFS could be described by a pseudo-first-order kinetic [...] Read more.
The green synthesis of silver nanoparticles (AgNPs) using the cell-free supernatant of a Haematococcus pluvialis culture (CFS) was implemented in the current study, under illumination conditions. The reduction of Ag+ to AgNPs by the CFS could be described by a pseudo-first-order kinetic equation at the temperature range tested. A high reaction rate during synthesis and stable AgNPs were obtained at 45 °C, while an alkaline pH (pH = 11.0) and a AgNO3 aqueous solution to CFS ratio of 90:10 (v/v) proved to be the most effective conditions in AgNPs synthesis. A metal precursor (AgNO3) at the concentration range tested (1–5 mM) was the limited reactant in the synthesis process. The synthesis of AgNPs was accomplished under static and agitated conditions. Continuous stirring enhanced the rate of reaction but induced aggregation at prolonged incubation times. Zeta potential and polydispersity index measurements indicated stable AgNPs and the majority of AgNPs formation occurred in the monodisperse phase. The X-ray diffraction (XRD) pattern revealed the face-centered cubic structure of the formed AgNPs, while TEM analysis revealed that the AgNPs were of a quasi-spherical shape with a size from 30 to 50 nm. The long-term stability of the AgNPs could be achieved in darkness and at 4 °C. In addition, the synthesized nanoparticles showed antibacterial activity against Escherichia coli. Full article
(This article belongs to the Special Issue Eco-Nanotechnology in Materials)
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19 pages, 2944 KiB  
Article
Particleboards with Recycled Material from Hemp-Based Panels
by Electra Papadopoulou, Iouliana Chrysafi, Konstantina Karidi, Andromachi Mitani and Dimitrios N. Bikiaris
Materials 2024, 17(1), 139; https://doi.org/10.3390/ma17010139 - 27 Dec 2023
Viewed by 948
Abstract
This research addresses the current need for sustainable solutions in the construction and furniture industries, with a focus on environmentally friendly particleboard. Particleboards were made from a mixture of virgin wood chips and hemp shives, which were then mechanically recycled and used to [...] Read more.
This research addresses the current need for sustainable solutions in the construction and furniture industries, with a focus on environmentally friendly particleboard. Particleboards were made from a mixture of virgin wood chips and hemp shives, which were then mechanically recycled and used to make new lightweight particleboards. Phenol–formaldehyde resin with 25% w/w phenol replacement by soybean flour (PFS) was used as the binder for the lignocellulosic materials. Laboratory analyses determined the resin properties, and FTIR confirmed the structure of the experimental PFS resin. The thermal properties of all the resins were evaluated using thermogravimetric analysis (TGA). The panels were manufactured using industrial simulation and tested for mechanical and physical properties in accordance with European standards. The FTIR study confirmed good adhesion, and the TGA showed improved thermal stability for the recycled biomass panels compared to virgin biomass panels. The study concludes that lightweight particleboards can be successfully produced from recycled hemp shive-based panels, providing a sustainable alternative to traditional materials in the construction industry. Full article
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14 pages, 5431 KiB  
Article
Advanced Integration of Glutathione-Functionalized Optical Fiber SPR Sensor for Ultra-Sensitive Detection of Lead Ions
by Jiale Wang, Kunpeng Niu, Jianguo Hou, Ziyang Zhuang, Jiayi Zhu, Xinyue Jing, Ning Wang, Binyun Xia and Lei Lei
Materials 2024, 17(1), 98; https://doi.org/10.3390/ma17010098 - 24 Dec 2023
Viewed by 815
Abstract
It is crucial to detect Pb2+ accurately and rapidly. This work proposes an ultra-sensitive optical fiber surface plasmon resonance (SPR) sensor functionalized with glutathione (GSH) for label-free detection of the ultra-low Pb2+ concentration, in which the refractive index (RI) sensitivity of [...] Read more.
It is crucial to detect Pb2+ accurately and rapidly. This work proposes an ultra-sensitive optical fiber surface plasmon resonance (SPR) sensor functionalized with glutathione (GSH) for label-free detection of the ultra-low Pb2+ concentration, in which the refractive index (RI) sensitivity of the multimode-singlemode-multimode (MSM) hetero-core fiber is largely enhanced by the gold nanoparticles (AuNPs)/Au film coupling SPR effect. The GSH is modified on the fiber as the sensing probe to capture and identify Pb2+ specifically. Its working principle is that the Pb2+ chemically reacts with deprotonated carboxyl groups in GSH through ligand bonding, resulting in the formation of stable and specific chelates, inducing the variation of the local RI on the sensor surface, which in turn leads to the SPR wavelength shift in the transmission spectrum. Attributing to the AuNPs, both the Au substrates can be fully functionalized with the GSH molecules as the probes, which largely increases the number of active sites for Pb2+ trapping. Combined with the SPR effect, the sensor achieves a sensitivity of 2.32 × 1011 nm/M and a limit of detection (LOD) of 0.43 pM. It also demonstrates exceptional specificity, stability, and reproducibility, making it suitable for various applications in water pollution, biomedicine, and food safety. Full article
(This article belongs to the Section Materials Chemistry)
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22 pages, 7099 KiB  
Article
Reprocessing Possibilities of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)–Hemp Fiber Composites Regarding the Material and Product Quality
by Wiesław Frącz, Andrzej Pacana, Dominika Siwiec, Grzegorz Janowski and Łukasz Bąk
Materials 2024, 17(1), 55; https://doi.org/10.3390/ma17010055 - 22 Dec 2023
Viewed by 514
Abstract
An important issue addressed in research on the assessment of the quality of polymer products is the quality of the polymer material itself and, in accordance with the idea of waste-free management, the impact of its repeated processing on its properties and the [...] Read more.
An important issue addressed in research on the assessment of the quality of polymer products is the quality of the polymer material itself and, in accordance with the idea of waste-free management, the impact of its repeated processing on its properties and the quality of the products. In this work, a biocomposite, based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with short hemp fibers, was obtained and repeatedly processed, which is a continuation of the research undertaken by the team in the field of this type of biocomposites. After subsequent stages of processing, the selected mechanical, processing and functional properties of the products were assessed. For this purpose, microscopic tests were carried out, mechanical properties were tested in static tensile and impact tests, viscosity curves were determined after subsequent processing cycles and changes in plastic pressure in the mold cavity were determined directly during processing. The results of the presented research confirm only a slight decrease in the mechanical properties of the produced type of biocomposite, even after it has been reprocessed five times, which gives extra weight to arguments for its commercialization as a substitute for petrochemical-based plastics. No significant changes were found in the used parameters and processing properties with the stages of processing, which allows for a predictable and stable manufacturing process using, for example, the injection molding process. Full article
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30 pages, 7029 KiB  
Review
Development and Future Trends of Protective Strategies for Magnesium Alloy Vascular Stents
by Dexiao Liu, Ke Yang and Shanshan Chen
Materials 2024, 17(1), 68; https://doi.org/10.3390/ma17010068 - 22 Dec 2023
Viewed by 808
Abstract
Magnesium alloy stents have been extensively studied in the field of biodegradable metal stents due to their exceptional biocompatibility, biodegradability and excellent biomechanical properties. Nevertheless, the specific in vivo service environment causes magnesium alloy stents to degrade rapidly and fail to provide sufficient [...] Read more.
Magnesium alloy stents have been extensively studied in the field of biodegradable metal stents due to their exceptional biocompatibility, biodegradability and excellent biomechanical properties. Nevertheless, the specific in vivo service environment causes magnesium alloy stents to degrade rapidly and fail to provide sufficient support for a certain time. Compared to previous reviews, this paper focuses on presenting an overview of the development history, the key issues, mechanistic analysis, traditional protection strategies and new directions and protection strategies for magnesium alloy stents. Alloying, optimizing stent design and preparing coatings have improved the corrosion resistance of magnesium alloy stents. Based on the corrosion mechanism of magnesium alloy stents, as well as their deformation during use and environmental characteristics, we present some novel strategies aimed at reducing the degradation rate of magnesium alloys and enhancing the comprehensive performance of magnesium alloy stents. These strategies include adapting coatings for the deformation of the stents, preparing rapid endothelialization coatings to enhance the service environment of the stents, and constructing coatings with self-healing functions. It is hoped that this review can help readers understand the development of magnesium alloy cardiovascular stents and solve the problems related to magnesium alloy stents in clinical applications at the early implantation stage. Full article
(This article belongs to the Special Issue Advances in the Corrosion and Protection of Metals (Second Volume))
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14 pages, 8542 KiB  
Article
Electrophysical Properties of the Three-Component Multiferroic Ceramic Composites
by Dariusz Bochenek, Przemysław Niemiec, Dagmara Brzezińska, Grzegorz Dercz and Marcin Wąs
Materials 2024, 17(1), 49; https://doi.org/10.3390/ma17010049 - 22 Dec 2023
Viewed by 524
Abstract
Using the free (pressureless) sintering method, multiferroic ceramic composites based on two ferroelectric materials, i.e., BaTiO3 (B) and Pb0.94Sr0.06 (Zr0.46Ti0.54)0.99Cr0.01O3 (P), and magnetic material, i.e., zinc–nickel ferrite (F) were obtained. [...] Read more.
Using the free (pressureless) sintering method, multiferroic ceramic composites based on two ferroelectric materials, i.e., BaTiO3 (B) and Pb0.94Sr0.06 (Zr0.46Ti0.54)0.99Cr0.01O3 (P), and magnetic material, i.e., zinc–nickel ferrite (F) were obtained. Three composite compositions (BP-F) were obtained with a constant 90/10 content (ferroelectric/magnetic) and a variable content of the ferroelectric component (B/P), i.e., 70/30, 50/50, and 30/70. Crystalline structure, microstructural, DC electrical conductivity, dielectric, and ferroelectric properties of multiferroic composites were investigated. The concept of a composite consisting of two ferroelectric components ensures the preservation of sufficiently high ferroelectric properties of multiferroic composites sintered by the free sintering method. Research has shown that the percentage of individual ferroelectric components in the composite significantly affects the functional properties and the entire set of physical parameters of the multiferroic BP-F composite. In the case of the dielectric parameters, the best results were obtained for the composition with a more significant amount of BaTiO3; i.e., permittivity is 1265, spontaneous polarization is 7.90 µC/cm2, and remnant polarization is 5.40 µC/cm2. However, the most advantageous set of performance parameters shows the composite composition of 50BP-F. Full article
(This article belongs to the Special Issue Advanced Materials and Technologies for Thermal Sprayed Coatings)
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14 pages, 8247 KiB  
Article
SrTiO3-SrVO3 Ceramics for Solid Oxide Fuel Cell Anodes: A Route from Oxidized Precursors
by Javier Macías, Jorge R. Frade and Aleksey A. Yaremchenko
Materials 2023, 16(24), 7638; https://doi.org/10.3390/ma16247638 - 14 Dec 2023
Cited by 1 | Viewed by 809
Abstract
Perovskite-type Sr(Ti,V)O3-δ ceramics are promising anode materials for natural gas- and biogas-fueled solid oxide fuel cells, but the instability of these phases under oxidizing conditions complicates their practical application. The present work explores approaches to the fabrication of strontium titanate-vanadate electrodes from [...] Read more.
Perovskite-type Sr(Ti,V)O3-δ ceramics are promising anode materials for natural gas- and biogas-fueled solid oxide fuel cells, but the instability of these phases under oxidizing conditions complicates their practical application. The present work explores approaches to the fabrication of strontium titanate-vanadate electrodes from oxidized precursors. Porous ceramics with the nominal composition SrTi1−yVyOz (y = 0.1–0.3) were prepared in air via a solid state reaction route. Thermal processing at temperatures not exceeding 1100 °C yielded composite ceramics comprising perovskite-type SrTiO3, pyrovanadate Sr2V2O7 and orthovanadate Sr3(VO4)2 phases, while increasing firing temperatures to 1250–1440 °C enabled the formation of SrTi1−yVyO3 perovskites. Vanadium was found to substitute into the titanium sublattice predominantly as V4+, even under oxidizing conditions at elevated temperatures. Both perovskite and composite oxidized ceramics exhibit moderate thermal expansion coefficients in air, 11.1–12.1 ppm/K at 30–1000 °C, and insignificant dimensional changes induced by reduction in a 10%H2-N2 atmosphere. The electrical conductivity of reduced perovskite samples remains comparatively low, ~10−1 S/cm at 900 °C, whereas the transformation of oxidized vanadate phases into high-conducting SrVO3−δ perovskites upon reduction results in enhancement in conductivity, which reaches ~3 S/cm at 900 °C in porous composite ceramics with nominal composition SrTi0.7V0.3Oz. The electrical performance of the composite is expected to be further improved by optimization of the processing route and microstructure to facilitate the reduction of the oxidized precursor and attain better percolation of the SrVO3 phase. Full article
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19 pages, 2026 KiB  
Article
Metal Organic Frameworks: Current State and Analysis of Their Use as Modifiers of the Vulcanization Process and Properties of Rubber
by Katarzyna Klajn, Tomasz Gozdek and Dariusz M. Bieliński
Materials 2023, 16(24), 7631; https://doi.org/10.3390/ma16247631 - 13 Dec 2023
Viewed by 709
Abstract
The interest in and application of metal organic frameworks (MOF) is increasing every year. These substances are widely used in many places, including the separation and storage of gases and energy, catalysis, electrochemistry, optoelectronics, and medicine. Their use in polymer technology is also [...] Read more.
The interest in and application of metal organic frameworks (MOF) is increasing every year. These substances are widely used in many places, including the separation and storage of gases and energy, catalysis, electrochemistry, optoelectronics, and medicine. Their use in polymer technology is also increasing, focusing mainly on the synthesis of MOF-polymer hybrid compounds. Due to the presence of metal ions in their structure, they can also serve as a component of the crosslinking system used for curing elastomers. This article presents the possibility of using zeolitic imidazolate framework ZIF-8 or MOF-5 as activators for sulfur vulcanization of styrene-butadiene rubber (SBR), replacing zinc oxide in conventional (CV) or effective (EF) curing systems to different extents. Their participation in the curing process and influence on the crosslinking density and structure, as well as the mechanical and thermal properties of the rubber vulcanizates, were examined. Full article
(This article belongs to the Special Issue Advanced Rubber Composites II)
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18 pages, 12761 KiB  
Article
Preparation and Characterization of Modified ZrO2/SiO2/Silicone-Modified Acrylic Emulsion Superhydrophobic Coating
by Jiaxin Ben, Peipei Wu, Yancheng Wang, Jie Liu and Yali Luo
Materials 2023, 16(24), 7621; https://doi.org/10.3390/ma16247621 - 13 Dec 2023
Viewed by 940
Abstract
Superhydrophobic coatings have increasingly become the focal point of research due to their distinctive properties like water resistance, wear resistance, and acid-base resilience. In pursuit of maximizing their efficiency, research has primarily revolved around refining the fabrication process and the composition of emulsion/nanoparticle [...] Read more.
Superhydrophobic coatings have increasingly become the focal point of research due to their distinctive properties like water resistance, wear resistance, and acid-base resilience. In pursuit of maximizing their efficiency, research has primarily revolved around refining the fabrication process and the composition of emulsion/nanoparticle coatings. We innovatively devised a superhydrophobic coating by employing a spraying technique. This involved integrating a γ-Methacryloyloxypropyltrimethoxysilane (KH570)-modified ZrO2/SiO2/silicone-modified acrylic emulsion. A comprehensive evaluation of this coating was undertaken using analytical instruments such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and confocal laser scanning microscopy (CLSM). The coating demonstrated exceptional performance across a range of tests, including wear, immersion, and anti-icing cleaning, showcasing notable wear resistance, sodium chloride corrosion resistance, self-cleaning efficiency, and thermal stability. In particular, one coating exhibited super-hydrophobic properties, with a high contact angle of 158.5 degrees and an impressively low rolling angle of 1.85 degrees. This remarkable combination of properties is attributed to the judicious selection of components, which significantly reinforced the mechanical strength of the coating. These enhancements make it highly suitable for industrial applications where self-cleaning, anti-icing, and anti-contamination capabilities are critical. Full article
(This article belongs to the Section Thin Films and Interfaces)
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14 pages, 8347 KiB  
Article
Wire Electrochemical Etching of Superhydrophobic Nickel Surfaces with Enhanced Corrosion Protection
by Binghan Wu, Defeng Yan, Junyi Lin and Jinlong Song
Materials 2023, 16(23), 7472; https://doi.org/10.3390/ma16237472 - 01 Dec 2023
Viewed by 615
Abstract
Superhydrophobic nickel surfaces have significant advantages in the field of corrosion protection compared with traditional nickel corrosion protection methods which need a toxic chemical corrosion inhibitor. Electrochemical etching, an ideal method for fabricating superhydrophobic nickel surfaces, was also limited by low current density, [...] Read more.
Superhydrophobic nickel surfaces have significant advantages in the field of corrosion protection compared with traditional nickel corrosion protection methods which need a toxic chemical corrosion inhibitor. Electrochemical etching, an ideal method for fabricating superhydrophobic nickel surfaces, was also limited by low current density, resulting in low processing efficiency. To overcome this limitation, we proposed a new method to fabricate a superhydrophobic nickel surface using a wire electrochemical etching method. The wire electrochemical etching method accomplished the etching process by sweeping a controlled wire cathode across the surface of the anode nickel plate in an environmentally friendly neutral electrolyte, NaCl. The superhydrophobic nickel sample with a contact angle of 153° and a rolling angle of 10° could be fabricated by wire electrochemical etching and modification. Additionally, the optimal parameters of the wire electrochemical etching and the principle of superhydrophobic surface formation had also been systematically investigated, respectively. Moreover, the superhydrophobic nickel surface had self-cleaning performance, antifouling performance, corrosion protection, and abrasion resistance. Wire electrochemical etching improves the current density of processing, which means that this method improves the processing efficiency for fabricating a superhydrophobic nickel surface. This work is expected to enrich the theory and technology for fabricating superhydrophobic nickel surfaces to improve the corrosion protection of nickel. Full article
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18 pages, 19065 KiB  
Article
Optical and Structural Properties of Aluminum Nitride Epi-Films at Room and High Temperature
by Yanlian Yang, Yao Liu, Lianshan Wang, Shuping Zhang, Haixia Lu, Yi Peng, Wenwang Wei, Jia Yang, Zhe Chuan Feng, Lingyu Wan, Benjamin Klein, Ian T. Ferguson and Wenhong Sun
Materials 2023, 16(23), 7442; https://doi.org/10.3390/ma16237442 - 30 Nov 2023
Viewed by 781
Abstract
The high-quality aluminum nitride (AlN) epilayer is the key factor that directly affects the performance of semiconductor deep-ultraviolet (DUV) photoelectronic devices. In this work, to investigate the influence of thickness on the quality of the AlN epilayer, two AlN-thick epi-film samples were grown [...] Read more.
The high-quality aluminum nitride (AlN) epilayer is the key factor that directly affects the performance of semiconductor deep-ultraviolet (DUV) photoelectronic devices. In this work, to investigate the influence of thickness on the quality of the AlN epilayer, two AlN-thick epi-film samples were grown on c-plane sapphire substrates. The optical and structural characteristics of AlN films are meticulously examined by using high-resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), a dual-beam ultraviolet-visible spectrophotometer, and spectroscopic ellipsometry (SE). It has been found that the quality of AlN can be controlled by adjusting the AlN film thickness. The phenomenon, in which the thicker AlNn film exhibits lower dislocations than the thinner one, demonstrates that thick AlN epitaxial samples can work as a strain relief layer and, in the meantime, help significantly bend the dislocations and decrease total dislocation density with the thicker epi-film. The Urbach’s binding energy and optical bandgap (Eg) derived by optical transmission (OT) and SE depend on crystallite size, crystalline alignment, and film thickness, which are in good agreement with XRD and SEM results. It is concluded that under the treatment of thickening film, the essence of crystal quality is improved. The bandgap energies of AlN samples obtained from SE possess larger values and higher accuracy than those extracted from OT. The Bose–Einstein relation is used to demonstrate the bandgap variation with temperature, and it is indicated that the thermal stability of bandgap energy can be improved with an increase in film thickness. It is revealed that when the thickness increases to micrometer order, the thickness has little effect on the change of Eg with temperature. Full article
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13 pages, 4908 KiB  
Article
Fabrication of Yttrium Oxide Hollow Films for Efficient Passive Radiative Cooling
by Heegyeom Jeon, Sohyeon Sung, Jeehoon Yu, Hyun Kim, Yong Seok Kim and Youngjae Yoo
Materials 2023, 16(23), 7373; https://doi.org/10.3390/ma16237373 - 27 Nov 2023
Viewed by 704
Abstract
In recent years, many parts of the world have researched the transition to renewable energy, reducing energy consumption and moving away from fossil fuels. Among the studies to reduce energy consumption, passive radiative cooling can reduce the energy used for building cooling, and [...] Read more.
In recent years, many parts of the world have researched the transition to renewable energy, reducing energy consumption and moving away from fossil fuels. Among the studies to reduce energy consumption, passive radiative cooling can reduce the energy used for building cooling, and to improve this, the optical properties of atmospheric window emissivity and solar reflectance must be increased. In this study, hollow yttrium oxide (H-Y2O3) was fabricated using melamine formaldehyde (MF) as a sacrificial template to improve the optical properties of passive radiative cooling. We then used finite-difference time-domain (FDTD) simulations to predict the optical properties of the fabricated particles. This study compares the properties of MF@Y(OH)CO3 and H-Y2O3 particles derived from the same process. H-Y2O3 was found to have a solar reflectance of 70.73% and an atmospheric window emissivity of 86.24%, and the field tests revealed that the temperature of MF@Y(OH)CO3 was relatively low during the daytime. At night, the temperature of the H-Y2O3 film was found to be 2.6 °C lower than the ambient temperature of 28.8 °C. The optical properties and actual cooling capabilities of the particles at each stage of manufacturing the hollow particles were confirmed and the cooling capabilities were quantified. Full article
(This article belongs to the Special Issue Advanced Electronic Devices for Biomedical Applications)
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14 pages, 10632 KiB  
Article
On Impact Damage and Repair of Composite Honeycomb Sandwich Structures
by Hang Zhang, Xiaopei Wang, Zhenhan Guo, Yuan Qian, Yan Shang and Deng’an Cai
Materials 2023, 16(23), 7374; https://doi.org/10.3390/ma16237374 - 27 Nov 2023
Viewed by 752
Abstract
This study is conducted on glass fiber-reinforced composite honeycomb sandwich structures by introducing delamination damage through low-velocity impact tests, establishing a three-dimensional progressive damage analysis model, and evaluating the delamination damage characteristics and laws of honeycomb sandwich structures under different impact energies through [...] Read more.
This study is conducted on glass fiber-reinforced composite honeycomb sandwich structures by introducing delamination damage through low-velocity impact tests, establishing a three-dimensional progressive damage analysis model, and evaluating the delamination damage characteristics and laws of honeycomb sandwich structures under different impact energies through experiments. Repair techniques and process parameters for delamination damage are explored. It is found that as the impact energy increases, the damage area of honeycomb sandwich panels also increases, and the delamination damage extends from the impact center to the surrounding areas, accompanied by damage such as fiber fracture and matrix cracking. The strength recovery rates of sandwich panels at impact energies of 5 J, 15 J, and 25 J after repair are 71.90%, 65.89%, and 67.10%, respectively, which has a considerable repair effect. In addition, a progressive damage model for low-velocity impact on the composite honeycomb sandwich structure is established, and its accuracy and reliability are verified. Full article
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16 pages, 3301 KiB  
Article
Lignin-Based Mesoporous Hollow Carbon@MnO2 Nanosphere Composite as an Anodic Material for Lithium-Ion Batteries
by Shun Li, Jianguo Huang and Guijin He
Materials 2023, 16(23), 7283; https://doi.org/10.3390/ma16237283 - 23 Nov 2023
Viewed by 726
Abstract
The lignin-based mesoporous hollow carbon@MnO2 nanosphere composites (L-C-NSs@MnO2) were fabricated by using lignosulfonate as the carbon source. The nanostructured MnO2 particles with a diameter of 10~20 nm were uniformly coated onto the surfaces of the [...] Read more.
The lignin-based mesoporous hollow carbon@MnO2 nanosphere composites (L-C-NSs@MnO2) were fabricated by using lignosulfonate as the carbon source. The nanostructured MnO2 particles with a diameter of 10~20 nm were uniformly coated onto the surfaces of the hollow carbon nanospheres. The obtained L-C-NSs@MnO2 nanosphere composite showed a prolonged cycling lifespan and excellent rate performance when utilized as an anode for LIBs. The L-C-NSs@MnO2 nanocomposite (24.6 wt% of MnO2) showed a specific discharge capacity of 478 mAh g−1 after 500 discharge/charge cycles, and the capacity contribution of MnO2 in the L-C-NSs@MnO2 nanocomposite was estimated ca. 1268.8 mAh g−1, corresponding to 103.2% of the theoretical capacity of MnO2 (1230 mAh g−1). Moreover, the capacity degradation rate was ca. 0.026% per cycle after long-term and high-rate Li+ insertion/extraction processes. The three-dimensional lignin-based carbon nanospheres played a crucial part in buffering the volumetric expansion and agglomeration of MnO2 nanoparticles during the discharge/charge processes. Furthermore, the large specific surface areas and mesoporous structure properties of the hollow carbon nanospheres significantly facilitate the fast transport of the lithium-ion and electrons, improving the electrochemical activities of the L-C-NSs@MnO2 electrodes. The presented work shows that the combination of specific structured lignin-based carbon nanoarchitecture with MnO2 provides a brand-new thought for the designation and synthesis of high-performance materials for energy-related applications. Full article
(This article belongs to the Section Materials Chemistry)
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16 pages, 7242 KiB  
Article
Graphene-Based Composites for Thermoelectric Applications at Room Temperature
by Sonya Harizanova, Vassil Vulchev and Radostina Stoyanova
Materials 2023, 16(23), 7262; https://doi.org/10.3390/ma16237262 - 21 Nov 2023
Viewed by 699
Abstract
The thermoelectric materials that operate at room temperature represent a scientific challenge in finding chemical compositions with three optimized, independent parameters, namely electrical and thermal conductivity and the Seebeck coefficient. Here, we explore the concept of the formation of hybrid composites between carbon-based [...] Read more.
The thermoelectric materials that operate at room temperature represent a scientific challenge in finding chemical compositions with three optimized, independent parameters, namely electrical and thermal conductivity and the Seebeck coefficient. Here, we explore the concept of the formation of hybrid composites between carbon-based materials and oxides, with the aim of modifying their thermoelectric performance at room temperature. Two types of commercially available graphene-based materials are selected: N-containing reduced graphene oxide (NrGO) and expanded graphite (ExGr). Although the NrGO displays the lowest thermal conductivity at room temperature, the ExGr is characterized by the lowest electrical resistivity and a negative Seebeck coefficient. As oxides, we choose two perspective thermoelectric materials: p-type Ca3Co4O9 and n-type Zn0.995Al0.005O. The hybrid composites were prepared by mechanical milling, followed by a pelleting. The thermoelectric efficiency was evaluated on the basis of its measured electrical resistivity, Seebeck coefficient and thermal conductivity at room temperature. It was found that that 2 wt.% of ExGr or NrGO leads to an enhancement of the thermoelectric activity of Ca3Co4O9, while, for Zn0.995Al0.005O, the amount of ExGr varies between 5 and 20 wt.%. The effect of the composites’ morphology on the thermoelectric properties is discussed on the basis of SEM/EDS experiments. Full article
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16 pages, 4193 KiB  
Article
A Yield Stress and Work Hardening Model of Al-Mg-Si Alloy Considering the Strengthening Effect of β” and β’ Precipitates
by Xiaoyu Zheng, Qi Huang, Hong Mao, Kai Li, Namin Xiao, Xingwu Li, Yong Du, Yuling Liu and Yi Kong
Materials 2023, 16(22), 7183; https://doi.org/10.3390/ma16227183 - 16 Nov 2023
Viewed by 816
Abstract
Precipitates are the primary source of strength for the Al-Mg-Si alloy. Aluminum alloy in the peak-aged state mainly contains β” and β’ precipitates. Most of the literature has only considered the strengthening effect of β”. Here, we develop a single-crystal intensity model including [...] Read more.
Precipitates are the primary source of strength for the Al-Mg-Si alloy. Aluminum alloy in the peak-aged state mainly contains β” and β’ precipitates. Most of the literature has only considered the strengthening effect of β”. Here, we develop a single-crystal intensity model including both precipitate enhancement effects for the first time. This model was subsequently implemented into a crystal plastic finite-element method to model the uniaxial tensile process of a polycrystalline aggregate model of Al-Mg-Si alloy. The simulation results for uniaxial stretching are in good agreement with the experimental results, confirming that the constitutive parameters used for the single-crystal strength model with two precipitates are based on realistic physical implications. Furthermore, by comparing the uniaxial tensile simulation results of a peak-aged alloy considering the actual precipitated phase composition of the alloy with those assuming that the precipitated phase is only the β” phase, the predicted tensile strength of the former is around 5.65% lower than that of the latter, suggesting that the two kinds of precipitation should be separately considered when simulating the mechanical response of Al-Mg-Si alloy. It is highly expected that the present simulation strategy is not limited to Al-Mg-Si alloys, and it can be equally applied to the other age-enhanced alloys. Full article
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18 pages, 5364 KiB  
Article
Study of the Chemical Vapor Deposition of Nano-Sized Carbon Phases on {001} Silicon
by Teodor Milenov, Dimitar Trifonov, Dobromir A. Kalchevski, Stefan Kolev, Ivalina Avramova, Stoyan Russev, Kaloyan Genkov, Georgi Avdeev, Dimitar Dimov, Desislava M. Karaivanova and Evgenia Valcheva
Materials 2023, 16(22), 7190; https://doi.org/10.3390/ma16227190 - 16 Nov 2023
Cited by 1 | Viewed by 943
Abstract
Different nano-sized phases were synthesized using chemical vapor deposition (CVD) processes. The deposition took place on {001} Si substrates at about 1150–1160 °C. The carbon source was thermally decomposed acetone (CH3)2CO in a main gas flow of argon. We [...] Read more.
Different nano-sized phases were synthesized using chemical vapor deposition (CVD) processes. The deposition took place on {001} Si substrates at about 1150–1160 °C. The carbon source was thermally decomposed acetone (CH3)2CO in a main gas flow of argon. We performed experiments at two ((CH3)2CO + Ar)/Ar) ratios and observed that two visually distinct types of layers were deposited after a one-hour deposition process. The first layer type, which appears more inhomogeneous, has areas of SiO2 (about 5% of the surface area substrates) beside shiny bright and rough paths, and its Raman spectrum corresponds to diamond-like carbon, was deposited at a (CH3)2CO+Ar)/Ar = 1/5 ratio. The second layer type, deposited at (CH3)2CO + Ar)/Ar = a 1/0 ratio, appears homogeneous and is very dark brown or black in color and its Raman spectrum pointed to defect-rich multilayered graphene. The performed structural studies reveal the presence of diamond and diamond polytypes and seldom SiC nanocrystals, as well as some non-continuously mixed SiC and graphene-like films. The performed molecular dynamics simulations show that there is no possibility of deposition of sp3-hybridized on sp2-hybridized carbon, but there are completely realistic possibilities of deposition of sp2- on sp2- and sp3- on sp3-hybridized carbon under different scenarios. Full article
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19 pages, 6987 KiB  
Article
Research on the Mechanical Model and Hysteresis Performance of a New Mild Steel-Rotational Friction Hybrid Self-Centering Damper
by Debin Wang, Ran Pang, Gang Wang and Guoxi Fan
Materials 2023, 16(22), 7168; https://doi.org/10.3390/ma16227168 - 15 Nov 2023
Cited by 1 | Viewed by 685
Abstract
A mild steel-friction self-centering damper with a hybrid energy-dissipation mechanism (MS-SCFD) was proposed, which consisted of a mild steel, frictional, dual-energy-dissipation system and a disc spring resetting system. The structure and principle of the MS-SCFD were explained in detail while the restoring force [...] Read more.
A mild steel-friction self-centering damper with a hybrid energy-dissipation mechanism (MS-SCFD) was proposed, which consisted of a mild steel, frictional, dual-energy-dissipation system and a disc spring resetting system. The structure and principle of the MS-SCFD were explained in detail while the restoring force model was established. The hysteretic behavior of the MS-SCFD under low-cycle reciprocating loading was modeled. Then, the influence of parameters such as the disc spring preload, the friction coefficient, and the soft-steel thickness on the mechanical properties of the MS-SCFD was investigated. The results indicate that the simulation results are basically consistent with the theoretical prediction results, with a maximum error of only 9.46% for the key points of bearing capacity. Since the MS-SCFD is provided with a hysteretic curve in the typical flag type, it will obtain the capacity of excellent self-centering performance. It can effectively enhance the stiffness, bearing capacity, and self-centering capability of the damper after the pre-pressure of the disc spring is increased. The energy-dissipation capacity of the MS-SCFD increases with the increase in the friction coefficient. However, it also increases the residual deformation of the MS-SCFD. The energy dissipation of the MS-SCFD is particularly sensitive to the thickness of mild steel. After being loaded, all components of the MS-SCFD are not damaged except for the plastic deformation caused by the yielding of the mild steel. The normal function of the MS-SCFD can be restored simply by replacing the mild steel plates after the earthquake. Therefore, it can significantly enhance the economy and applicability of the damper. Full article
(This article belongs to the Special Issue Structure and Mechanical Properties of Alloys, Volume III)
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14 pages, 2807 KiB  
Article
Influence of NF3 Plasma-Treated HfO2 Gate Insulator Surface on Tin Oxide Thin-Film Transistors
by Christophe Avis and Jin Jang
Materials 2023, 16(22), 7172; https://doi.org/10.3390/ma16227172 - 15 Nov 2023
Viewed by 769
Abstract
We studied the impact of NF3 plasma treatment on the HfO2 gate insulator of amorphous tin oxide (a-SnOx) thin-film transistors (TFTs). The plasma treatment was for 0, 10, or 30 s. The HfO2 insulator demonstrated a slightly higher [...] Read more.
We studied the impact of NF3 plasma treatment on the HfO2 gate insulator of amorphous tin oxide (a-SnOx) thin-film transistors (TFTs). The plasma treatment was for 0, 10, or 30 s. The HfO2 insulator demonstrated a slightly higher breakdown voltage, whereas the capacitance value remained almost constant (~150 nF/cm2). The linear mobility slightly increased from ~30 to ~35 cm2/Vs when the treatment time increased from 0 to 10 s, whereas a 30 s-treated TFT demonstrated a decreased mobility of ~15 cm2/Vs. The subthreshold swing and the threshold voltage remained in the 100–120 mV/dec. range and near 0 V, respectively. The hysteresis dramatically decreased from ~0.5 V to 0 V when a 10 s treatment was applied, and the 10 s-treated TFT demonstrated the best stability under high current stress (HCS) of 100 μA. The analysis of the tin oxide thin film crystallinity and oxygen environment demonstrated that the a-SnOx remained amorphous, whereas more metal–oxygen bonds were formed with a 10 s NF3 plasma treatment. We also demonstrate that the density of states (DOS) significantly decreased in the 10 s-treated TFT compared to the other conditions. The stability under HCS was attributed to the HfO2/a-SnOx interface quality. Full article
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15 pages, 4127 KiB  
Article
Analysis of the Effect of Skew Rolling Parameters on the Surface Roughness of C60 Steel Products Using ML Methods
by Konrad Lis
Materials 2023, 16(22), 7136; https://doi.org/10.3390/ma16227136 - 12 Nov 2023
Viewed by 748
Abstract
This paper presents results from experimental and numerical studies of the skew rolling process used to shape axisymmetric products made of C60-grade steel. An experimental study was carried out to investigate the effect of process parameters described by the forming angle α, [...] Read more.
This paper presents results from experimental and numerical studies of the skew rolling process used to shape axisymmetric products made of C60-grade steel. An experimental study was carried out to investigate the effect of process parameters described by the forming angle α, the skew angle θ, the reduction ratio δ, and the jaw chuck velocity Vu on the surface roughness Ra of the forgings. Stepped forgings made of C60-grade steel were rolled. Based on numerical calculations, a machine learning regression model was developed that uses process parameters to predict the surface roughness of produced parts. The random forest model was found to be the most effective based on the determined metrics (MAE, RMSE, R2). A more detailed analysis of this model was performed using the SHAP library. The application of ML methods will enable optimization of skew rolling through appropriate selection of process parameters affecting improvement in product quality. Full article
(This article belongs to the Special Issue Advanced Manufacturing Processes of Metal Forming)
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11 pages, 2303 KiB  
Article
Tailoring the Structure and Properties of Epitaxial Europium Tellurides on Si(100) through Substrate Temperature Control
by Fan Yu, Xiaodong Qiu, Jinming Zhou, Lin Huang, Bin Yang, Junming Liu, Di Wu, Gan Wang and Yi Zhang
Materials 2023, 16(22), 7093; https://doi.org/10.3390/ma16227093 - 09 Nov 2023
Viewed by 709
Abstract
In this study, we improved the growth procedure of EuTe and realized the epitaxial growth of EuTe4. Our research demonstrated a selective growth of both EuTe and EuTe4 on Si(100) substrates using the molecular beam epitaxy (MBE) technique and reveals [...] Read more.
In this study, we improved the growth procedure of EuTe and realized the epitaxial growth of EuTe4. Our research demonstrated a selective growth of both EuTe and EuTe4 on Si(100) substrates using the molecular beam epitaxy (MBE) technique and reveals that the substrate temperature plays a crucial role in determining the structural phase of the grown films: EuTe can be obtained at a substrate temperature of 220 °C while lowering down the temperature to 205 °C leads to the formation of EuTe4. A comparative analysis of the transmittance spectra of these two films manifested that EuTe is a semiconductor, whereas EuTe4 exhibits charge density wave (CDW) behavior at room temperature. The magnetic measurements displayed the antiferromagnetic nature in EuTe and EuTe4, with Néel temperatures of 10.5 and 7.1 K, respectively. Our findings highlight the potential for controllable growth of EuTe and EuTe4 thin films, providing a platform for further exploration of magnetism and CDW phenomena in rare earth tellurides. Full article
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13 pages, 3240 KiB  
Article
Effect of the Solid Solution and Aging Treatment on the Mechanical Properties and Microstructure of a Novel Al-Mg-Si Alloy
by Yan Chen, Wu Wei, Yu Zhao, Wei Shi, Xiaorong Zhou, Li Rong, Shengping Wen, Xiaolan Wu, Kunyuan Gao, Hui Huang and Zuoren Nie
Materials 2023, 16(21), 7036; https://doi.org/10.3390/ma16217036 - 04 Nov 2023
Cited by 3 | Viewed by 881
Abstract
A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and [...] Read more.
A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and strengthening mechanism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques are employed to examine the changes in the microstructure resulting from various solid solution treatments and aging treatments. The best strengthening effect can be achieved when the solubility of the MgSi phase and precipitate β″ (Mg2Si phase) is at their maximum. The addition of Er and Zr elements promotes the precipitation of the β″ phase and makes the b″ phase more finely dispersed. The aging strengthening of alloys is a comprehensive effect of the dislocation cutting mechanism and bypass mechanism, the joint effect of diffusion strengthening of Al3(Er,Zr) particles and the addition of Er and Zr elements promoting the precipitation strengthening of β″ phases. In this paper, by adding Er and Zr elements and exploring the optimal heat treatment system, the yield strength of the alloy reaches 437 MPa and the tensile strength reaches 453 MPa after solid solution treatment at 565 °C/30 min and aging at 175 °C/10 h. Full article
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12 pages, 7966 KiB  
Article
MOF-808 as an Efficient Catalyst for Valorization of Biodiesel Waste Production: Glycerol Acetalization
by Fátima Mirante, Pedro Leo, Catarina N. Dias, Luís Cunha-Silva and Salete S. Balula
Materials 2023, 16(21), 7023; https://doi.org/10.3390/ma16217023 - 03 Nov 2023
Viewed by 1090
Abstract
Glycerol is the main residue in the biodiesel production industry; therefore, their valorization is crucial. The acetalization of glycerol toward fuel additives such as solketal (2,2-dimethyl-1,3-dioxolan-4-methanol) is of high interest, promoting circular economy since it can be added to biodiesel or even fossil [...] Read more.
Glycerol is the main residue in the biodiesel production industry; therefore, their valorization is crucial. The acetalization of glycerol toward fuel additives such as solketal (2,2-dimethyl-1,3-dioxolan-4-methanol) is of high interest, promoting circular economy since it can be added to biodiesel or even fossil diesel to improve their quality and efficiency. Straightforward-prepared metal–organic framework (MOF) materials of the MOF-808 family were applied to the valorization of glycerol for the first time. In particular, MOF-808(Hf) was revealed to be an effective heterogeneous catalyst to produce solketal under moderate conditions: a small amount of the MOF material (only 4 wt% of glycerol), a 1:6 ratio of glycerol/acetone, and a temperature of 333 K. The high efficiency of MOF-808(Hf) was associated with the high amount of acid centers present in its structure. Furthermore, its structural characteristics, such as window opening cavity size and pore diameters, were shown to be ideal for reusing this material for at least ten consecutive reaction cycles without losing activity (conversion > 90% and selectivity > 98%). Remarkably, it was not necessary to wash or activate the MOF-808(Hf) catalyst between cycles (no pore blockage occurred), and it maintained structural integrity after ten cycles, confirming its ability to be a sustainable heterogeneous catalyst for glycerol valorization. Full article
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17 pages, 8119 KiB  
Article
Unsupervised Deep Learning for Advanced Forming Limit Analysis in Sheet Metal: A Tensile Test-Based Approach
by Aleksandra Thamm, Florian Thamm, Annette Sawodny, Sally Zeitler, Marion Merklein and Andreas Maier
Materials 2023, 16(21), 7001; https://doi.org/10.3390/ma16217001 - 01 Nov 2023
Viewed by 1019
Abstract
An accurate description of the formability and failure behavior of sheet metal materials is essential for an optimal forming process design. In this respect, the forming limit curve (FLC) based on the Nakajima test, which is determined in accordance with DIN EN ISO [...] Read more.
An accurate description of the formability and failure behavior of sheet metal materials is essential for an optimal forming process design. In this respect, the forming limit curve (FLC) based on the Nakajima test, which is determined in accordance with DIN EN ISO 12004-2, is a wide-spread procedure for evaluating the formability of sheet metal materials. Thereby the FLC is affected by influences originating from intrinsic factors of the Nakajima test-setup, such as friction, which leads to deviations from the linear strain path, biaxial prestress and bending superposition. These disadvantages can be circumvented by an alternative test combination of uniaxial tensile test and hydraulic bulge test. In addition, the forming limit capacity of many lightweight materials is underestimated using the cross-section method according to DIN EN ISO 12004-2, due to the material-dependent occurrence of multiple strain maxima during forming or sudden cracking without prior necking. In this regard, machine learning approaches have a high potential for a more accurate determination of the forming limit curve due to the inclusion of other parameters influencing formability. This work presents a machine learning approach focused on uniaxial tensile tests to define the forming limit of lightweight materials and high-strength steels. The transferability of an existing weakly supervised convolutional neural network (CNN) approach was examined, originally designed for Nakajima tests, to uniaxial tensile tests. Additionally, a stereo camera-based method for this purpose was developed. In our evaluation, we train and test materials, including AA6016, DX54D, and DP800, through iterative data composition, using cross-validation. In the context of our stereo camera-based approach, strains for different materials and thicknesses were predicted. In this cases, our method successfully predicted the major strains with close agreement to ISO standards. For DX54D, with a thickness of 0.8 mm, the prediction was 0.659 (compared to ISO’s 0.664). Similarly, for DX54D, 2.0 mm thickness, the predicted major strain was 0.780 (compared to ISO 0.705), and for AA6016, at 1.0 mm thickness, a major strain of 0.314 (in line with ISO 0.309) was estimated. However, for DP800 with a thickness of 1.0 mm, the prediction yielded a major strain of 0.478 (as compared to ISO 0.289), indicating a divergence from the ISO standard in this particular case. These results in general, generated with the CNN stereo camera-based approach, underline the quantitative alignment of the approach with the cross-section method. Full article
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17 pages, 7395 KiB  
Article
Influence of Surface Preparation on the Microstructure and Mechanical Properties of Cold-Sprayed Nickel Coatings on Al 7075 Alloy
by Wojciech Żórawski, Anna Góral, Medard Makrenek, Lidia Lityńska-Dobrzyńska and Paweł Czaja
Materials 2023, 16(21), 7002; https://doi.org/10.3390/ma16217002 - 01 Nov 2023
Viewed by 650
Abstract
This work presents the effect of surface roughness (Al 7075) on the microstructure and mechanical properties of cold-sprayed nickel coatings. Coating analysis included substrate surfaces and coating geometry, microstructure characterization, microhardness, nanohardness, elastic modulus, and adhesion. The results show that the surface preparation [...] Read more.
This work presents the effect of surface roughness (Al 7075) on the microstructure and mechanical properties of cold-sprayed nickel coatings. Coating analysis included substrate surfaces and coating geometry, microstructure characterization, microhardness, nanohardness, elastic modulus, and adhesion. The results show that the surface preparation had a significant effect on coating adhesion and microstructure. The coating deposited at the highest gas temperature revealed a dense microstructure, showing very good adhesion of the impacting powder particles to the substrate and good bonding between deposited layers. The Ni grains with different shapes (elongated, equiaxed) and sizes of a few dozen to several hundred nanometres were present in the splats. An increase in temperature caused significant growth in coating thickness as a result of the powder grains’ higher velocity. Moreover, higher gas temperature resulted in the enhancement of micro- and nanohardness, elastic modulus, and adhesion. The adhesive bond strength of Ni coatings in the tested temperature ranges from 500 °C to 800 °C increased with the increase in the surface roughness of the substrate. For the Al 7075 coarse grit-blasted (CG) substrate with the highest roughness, the adhesion reached the highest value of 44.6 MPa when the working gas was at a temperature of 800 °C. There were no distinct dependencies of surface roughness and thickness on the mechanical properties of the cold-sprayed nickel coating. Full article
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18 pages, 11760 KiB  
Article
Sintered Brake Pads Failure in High-Energy Dissipation Braking Tests: A Post-Mortem Mechanical and Microstructural Analysis
by Alexandre Mege-Revil, Jessie Rapontchombo-Omanda, Itziar Serrano-Munoz, Anne-Lise Cristol, Vincent Magnier and Philippe Dufrenoy
Materials 2023, 16(21), 7006; https://doi.org/10.3390/ma16217006 - 01 Nov 2023
Cited by 2 | Viewed by 849
Abstract
The industrial sintering process used to produce metallic matrix pads has been altered to diminish the amount of copper used. Unfortunately, replacing a large part of the copper with iron seems to have reached a limit. In the high-energy, emergency-type rail braking used [...] Read more.
The industrial sintering process used to produce metallic matrix pads has been altered to diminish the amount of copper used. Unfortunately, replacing a large part of the copper with iron seems to have reached a limit. In the high-energy, emergency-type rail braking used in this study, the materials are put to the very limit of their usage capacity, allowing us to observe the evolution of the microstructure and mechanical properties of sintered, metallic matrix pads. After the braking test, their compressive behaviour was assessed using digital image correlation (DIC), and their microstructure with scanning electron microscopy (SEM). The worn material has three flat layers with different microstructures and compressive behaviours. The bottom layer seems unmodified. Macroscopic and microscopic cracks run through the intermediate layer (2–15 mm depth). The top layer has stiffened thanks to resolidification of copper. The temperature reaches 1000 °C during the braking test, which also explains the carbon diffusion into iron that result in the weakening of iron –graphite interfaces in the pad. Finally, submicronic particles are detected at many open interfaces of the worn and compressed pad. Associated with the predominant role of graphite particles, this explains the weak compressive behaviour of the pads. Full article
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13 pages, 4111 KiB  
Article
Synergetic Effect and Phase Engineering by Formation of Ti3C2Tx Modified 2H/1T-MoSe2 Composites for Enhanced HER
by Lei Xiao, Qichao Yang, Xiangyang Zhu, Yang Wei and Jing Wang
Materials 2023, 16(21), 6991; https://doi.org/10.3390/ma16216991 - 31 Oct 2023
Cited by 1 | Viewed by 801
Abstract
The typical semi conductivity and few active sites of hydrogen evolution of 2H MoSe2 severely restrict its electrocatalytic hydrogen evolution performance. At the same time, the 1T MoSe2 has metal conductivity and plentiful hydrogen evolution sites, making it feasible to optimize [...] Read more.
The typical semi conductivity and few active sites of hydrogen evolution of 2H MoSe2 severely restrict its electrocatalytic hydrogen evolution performance. At the same time, the 1T MoSe2 has metal conductivity and plentiful hydrogen evolution sites, making it feasible to optimize the electrocatalytic hydrogen evolution behavior of MoSe2 using phase engineering. In this study, we, through a simple one-step hydrothermal method, composed 1T/2H MoSe2, and then used newly emerging transition metal carbides with several atomic-layer thicknesses Ti3C2Tx to improve the conductivity of a MoSe2-based electrocatalyst. Finally, MoSe2@Ti3C2Tx was successfully synthesized, according to the control of the additional amount of Ti3C2Tx, to form a proper MoSe2/ Ti3C2Tx heterostructure with a better electrochemical HER performance. As obtained MoSe2@4 mg-Ti3C2Tx achieved a low overpotential, a small Tafel slope and this work offers additional insight into broadened MoSe2 and MXenes-based catalyst’s electrochemical application. Full article
(This article belongs to the Special Issue Electrochemical Material Science and Electrode Processes)
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11 pages, 4019 KiB  
Article
Study on the Stability of Cu-Ni Cluster Components and the Effect of Strain on Its Structure
by Xiaochuan Zeng, Cuizhu He, Xuejun Li and Qiaodan Hu
Materials 2023, 16(21), 6952; https://doi.org/10.3390/ma16216952 - 30 Oct 2023
Viewed by 699
Abstract
Solute clusters are one of the important mechanisms of irradiation embrittlement of ferritic steels. It is of great significance to study the stability of solute clusters in ferritic steels and their effects on the mechanical properties of the materials. Molecular dynamics was used [...] Read more.
Solute clusters are one of the important mechanisms of irradiation embrittlement of ferritic steels. It is of great significance to study the stability of solute clusters in ferritic steels and their effects on the mechanical properties of the materials. Molecular dynamics was used to study the binding energy, defect energy, and interaction energy of 2 nm-diameter Cu-Ni clusters in the ferritic lattice, which have six categories of Cu-Ni clusters, such as the pure Cu cluster, the core–shell structural cluster with one layer to four layers of Ni atoms and the pure Ni cluster. It was found that Cu-Ni clusters have lower energy advantages than pure Ni clusters. Through shear strain simulation of the three clusters, the structure of 2 nm diameter clusters does not undergo phase transformation. The number of slip systems and the length of dislocation lines in the cluster system are positively correlated with the magnitude of the critical stress of material plastic deformation. Full article
(This article belongs to the Special Issue Key Materials in Nuclear Reactors)
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22 pages, 4675 KiB  
Article
Screening Ba0.9A0.1MnO3 and Ba0.9A0.1Mn0.7Cu0.3O3 (A = Mg, Ca, Sr, Ce, La) Sol-Gel Synthesised Perovskites as GPF Catalysts
by Nawel Ghezali, Álvaro Díaz Verde and María José Illán Gómez
Materials 2023, 16(21), 6899; https://doi.org/10.3390/ma16216899 - 27 Oct 2023
Cited by 3 | Viewed by 772
Abstract
Ba0.9A0.1MnO3 (BM-A) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) (A = Mg, Ca, Sr, Ce, La) perovskite-type mixed oxides were synthesised, characterised, and used for soot oxidation in simulated Gasoline Direct Injection (GDI) [...] Read more.
Ba0.9A0.1MnO3 (BM-A) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) (A = Mg, Ca, Sr, Ce, La) perovskite-type mixed oxides were synthesised, characterised, and used for soot oxidation in simulated Gasoline Direct Injection (GDI) engine exhaust conditions. The samples have been obtained by the sol-gel method in an aqueous medium and deeply characterised. The characterization results indicate that the partial substitution of Ba by A metal in BaMnO3 (BM) and BaMn0.7Cu0.3O3 (BMC) perovskites: (i) favours the hexagonal structure of perovskite; (ii) improves the reducibility and the oxygen desorption during Temperature-Programmed Desorption (O2-TPD) tests and, consequently, the oxygen mobility; (iii) mantains the amount of oxygen vacancies and of Mn(IV) and Mn(III) oxidation states, being Mn(IV) the main one; and (iv) for Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) series, copper is partially incorporated into the structure. The soot conversion data reveal that Ba0.9La0.1Mn0.7Cu0.3O3 (BMC-La) is the most active catalyst in an inert (100% He) reaction atmosphere, as it presents the highest amount of copper on the surface, and that Ba0.9Ce0.1MnO3 (BM-Ce) is the best one if a low amount of O2 (1% O2 in He) is present, as it combines the highest emission of oxygen with the good redox properties of Ce(IV)/Ce(III) and Mn(IV)/Mn(III) pairs. Full article
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13 pages, 4155 KiB  
Article
Cyclic Voltammetry of C.I. Disperse Orange 62 in an Aqueous Electrolyte
by Thomas Bechtold, Noemí Aguiló-Aguayo and Tung Pham
Materials 2023, 16(21), 6901; https://doi.org/10.3390/ma16216901 - 27 Oct 2023
Viewed by 649
Abstract
Disperse dyes are an important group of colorants for dyeing polyester fibers. Approximately 30.000 tons of disperse dyes are released into the waste water annually from spent dyebaths. Therefore, methods for decolorizing such dyes are of general interest. The reductive after-treatment of disperse [...] Read more.
Disperse dyes are an important group of colorants for dyeing polyester fibers. Approximately 30.000 tons of disperse dyes are released into the waste water annually from spent dyebaths. Therefore, methods for decolorizing such dyes are of general interest. The reductive after-treatment of disperse dyes using reducing agents, such as Na2S2O4, is a widely used process to improve rub fastness through dye reduction. Electrochemical dye reduction could be an alternative process for reductive dye treatment. In this work C.I. Disperse Orange 62 was used as a representative dye to study the direct cathodic reduction of a disperse dye with cyclic voltammetry. As anticipated for dispersed organic matter, relatively low current densities were observed, which strongly depend on the state of dispersion of the dye. The current density was increased by using dispersions prepared through dye precipitation from DMF solution and by the use of N-cetyl-N,N,N,-trimethyl-ammonium bromide as a cationic surfactant. The results demonstrate the successful cathodic reduction of a dispersed organic dye; however, the low solubility of the reaction products in the aqueous electrolyte hinders an efficient cathodic dye reduction. Full article
(This article belongs to the Special Issue Electrochemistry of Organic Compounds and Their Applications)
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11 pages, 627 KiB  
Article
Analysis of Stress Concentration in Functionally Graded Plates with Linearly Increasing Young’s Modulus
by Hassan Mohamed Abdelalim Abdalla, Daniele Casagrande and Francesco De Bona
Materials 2023, 16(21), 6882; https://doi.org/10.3390/ma16216882 - 26 Oct 2023
Viewed by 734
Abstract
In this article, the strain and stress analyses of functionally graded plates with circular holes that are subject to a uniaxial far-field traction load are analytically considered. The Young’s modulus is assumed to vary linearly along the radial direction around the hole. The [...] Read more.
In this article, the strain and stress analyses of functionally graded plates with circular holes that are subject to a uniaxial far-field traction load are analytically considered. The Young’s modulus is assumed to vary linearly along the radial direction around the hole. The adoption of such a type of inhomogeneity variation can be justified as follows. Firstly, and among all the possible variations of stiffness, the linear one is indeed the simplest inhomogeneity distribution. Surprisingly however, according to our knowledge extent, the associated elastic fields were not yet addressed in the literature. Secondly, a linearly varying stiffness could reasonably imply a remarkable advantage from a technological point of view. In fact, unlike nonlinearly varying stiffness plates, manufacturing routes are only required to handle constant variations throughout the radial domain. After recalling the basic equations for plane stress elasticity, the displacement, strain, and stress fields around the hole were numerically tackled and discussed for different stiffness ratios. A comparison was also carried out with other Young’s modulus distributions that have been commonly employed in the literature. Full article
(This article belongs to the Section Advanced Composites)
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17 pages, 5028 KiB  
Article
Synthesis and Characterization of Bioactive Glass and Zinc Oxide Nanoparticles with Enamel Remineralization and Antimicrobial Capabilities
by Ryota Nagasaki, Keiji Nagano, Takashi Nezu and Masahiro Iijima
Materials 2023, 16(21), 6878; https://doi.org/10.3390/ma16216878 - 26 Oct 2023
Viewed by 850
Abstract
Background: We investigated the effect of bioactive glass and zinc oxide nanoparticles on enamel remineralization, as well as their antimicrobial effect on cariogenic microbes. This is the first study that investigated the properties of bioactive glass and zinc oxide nanoparticles with mixed materials. [...] Read more.
Background: We investigated the effect of bioactive glass and zinc oxide nanoparticles on enamel remineralization, as well as their antimicrobial effect on cariogenic microbes. This is the first study that investigated the properties of bioactive glass and zinc oxide nanoparticles with mixed materials. Methods: Fluoride gel (F), bioactive glass microparticles (µB), bioactive glass nanoparticles (nB), zinc oxide nanoparticles (Z), and a mixed suspension of nB and Z (nBZ) were prepared and characterized by scanning and transmission electron microscopy, zeta potential measurement, X-ray diffraction, and acid buffering capacity testing. Further, we performed a remineralization cycle test of 28 days, and nanoindentation testing was carried out during the immersion period, and then the enamel surfaces were examined using scanning electron microscopy. Additionally, the antimicrobial effects of the sample suspensions were evaluated by measuring their minimum microbicidal concentrations against various cariogenic microbes. Results: Our results revealed that nB had a near-circular shape with an amorphous structure and a considerably large specific surface area due to nanoparticulation. Additionally, nB possessed a rapid acid buffering capacity that was comparable to that of μB. In the remineralization test, faster recovery of mechanical properties was observed on the enamel surface immersed in samples containing bioactive glass nanoparticles (nB and nBZ). After remineralization, demineralized enamel immersed in any of the samples showed a rough and porous surface structure covered with mineralized structures. Furthermore, nBZ exhibited a broad antimicrobial spectrum. Conclusions: These results demonstrated that bioactive glass and zinc oxide nanoparticles have superior demineralization-suppressing and remineralization-promoting effects. Full article
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16 pages, 4388 KiB  
Article
Durability Analysis of CFRP Adhesive Joints: A Study Based on Entropy Damage Modeling Using FEM
by Yutong Li, Huachao Deng, Maruri Takamura and Jun Koyanagi
Materials 2023, 16(20), 6821; https://doi.org/10.3390/ma16206821 - 23 Oct 2023
Cited by 2 | Viewed by 857
Abstract
Experimental methodologies for fatigue lifetime prediction are time-intensive and susceptible to environmental variables. Although the cohesive zone model is popular for predicting adhesive fatigue lifetime, entropy-based methods have also displayed potential. This study aims to (1) provide an understanding of the durability characteristics [...] Read more.
Experimental methodologies for fatigue lifetime prediction are time-intensive and susceptible to environmental variables. Although the cohesive zone model is popular for predicting adhesive fatigue lifetime, entropy-based methods have also displayed potential. This study aims to (1) provide an understanding of the durability characteristics of carbon fiber-reinforced plastic (CFRP) adhesive joints by incorporating an entropy damage model within the context of the finite element method and (2) examine the effects of different adhesive layer thicknesses on single-lap shear models. As the thickness of the adhesive layer increases, damage variables initially increase and then decrease. These peak at 0.3 mm. This observation provides a crucial understanding of the stress behavior at the resin–CFRP interface and the fatigue mechanisms of the resin. Full article
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30 pages, 5370 KiB  
Article
A Method for Predicting the Creep Rupture Life of Small-Sample Materials Based on Parametric Models and Machine Learning Models
by Xu Zhang, Jianyao Yao, Yulin Wu, Xuyang Liu, Changyin Wang and Hao Liu
Materials 2023, 16(20), 6804; https://doi.org/10.3390/ma16206804 - 22 Oct 2023
Viewed by 1180
Abstract
In view of the differences in the applicability and prediction ability of different creep rupture life prediction models, we propose a creep rupture life prediction method in this paper. Various time–temperature parametric models, machine learning models, and a new method combining time–temperature parametric [...] Read more.
In view of the differences in the applicability and prediction ability of different creep rupture life prediction models, we propose a creep rupture life prediction method in this paper. Various time–temperature parametric models, machine learning models, and a new method combining time–temperature parametric models with machine learning models are used to predict the creep rupture life of a small-sample material. The prediction accuracy of each model is quantitatively compared using model evaluation indicators (RMSE, MAPE, R2), and the output values of the most accurate model are used as the output values of the prediction method. The prediction method not only improves the applicability and accuracy of creep rupture life predictions but also quantifies the influence of each input variable on creep rupture life through the machine learning model. A new method is proposed in order to effectively take advantage of both advanced machine learning models and classical time–temperature parametric models. Parametric equations of creep rupture life, stress, and temperature are obtained using different time–temperature parametric models; then, creep rupture life data, obtained via equations under other temperature and stress conditions, are used to expand the training set data of different machine learning models. By expanding the data of different intervals, the problem of the low accuracy of the machine learning model for the small-sample material is solved. Full article
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13 pages, 11044 KiB  
Article
Tellurium Corrosion of Type 304/304L Stainless Steel, Iron, Chromium, and Nickel in High-Temperature Liquid Sodium
by Yi Xie
Materials 2023, 16(20), 6798; https://doi.org/10.3390/ma16206798 - 21 Oct 2023
Viewed by 719
Abstract
Investigating tellurium (Te) corrosion on structural materials is crucial for sodium-cooled fast reactors (SFRs) due to radionuclide presence and knowledge gaps. In this study, Type 304/304L stainless steel (SS304), chromium (Cr), iron (Fe), and nickel (Ni) samples were immersed in low-oxygen environments with [...] Read more.
Investigating tellurium (Te) corrosion on structural materials is crucial for sodium-cooled fast reactors (SFRs) due to radionuclide presence and knowledge gaps. In this study, Type 304/304L stainless steel (SS304), chromium (Cr), iron (Fe), and nickel (Ni) samples were immersed in low-oxygen environments with Te in liquid sodium at 773 K for 30 days. At 10 ppm oxygen, SS304 showed multiple oxide layers, including a compact NaCrO2 interlayer and porous Na-Fe-Ni-O outer layers. Tellurium penetrated through the porous layers but was hindered by the NaCrO2 interlayer. At 0.01 ppm oxygen, Cr had no oxide layer, while Fe and Ni had unstable ones. Tellurium-induced pitting was deeper in Fe and Ni compared to Cr. Oxygen levels and Cr composition are critical factors affecting stable oxide compound layer formation and mitigating Te-induced pitting. Full article
(This article belongs to the Section Corrosion)
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