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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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14 pages, 2906 KiB  
Article
First-Principles Study of Adsorption of CH4 on a Fluorinated Model NiF2 Surface
by Tilen Lindič and Beate Paulus
Materials 2024, 17(9), 2062; https://doi.org/10.3390/ma17092062 - 27 Apr 2024
Viewed by 630
Abstract
Electrochemical fluorination on nickel anodes, also known as the Simons’ process, is an important fluorination method used on an industrial scale. Despite its success, the mechanism is still under debate. One of the proposed mechanisms involves higher valent nickel species formed on an [...] Read more.
Electrochemical fluorination on nickel anodes, also known as the Simons’ process, is an important fluorination method used on an industrial scale. Despite its success, the mechanism is still under debate. One of the proposed mechanisms involves higher valent nickel species formed on an anode acting as effective fluorinating agents. Here we report the first attempt to study fluorination by means of first principles investigation. We have identified a possible surface model from the simplest binary nickel fluoride (NiF2). A twice oxidized NiF2(F2) (001) surface exhibits higher valent nickel centers and a fluorination source that can be best characterized as an [F2]− like unit, readily available to aid fluorination. We have studied the adsorption of CH4 and the co-adsorption of CH4 and HF on this surface by means of periodic density functional theory. By the adsorption of CH4, we found two main outcomes on the surface. Unreactive physisorption of CH4 and dissociative chemisorption resulting in the formation of CH3F and HF. The co-adsorption with the HF gave rise to four main outcomes, namely the formation of CH3F, CH2F2, CH3 radical, and also physisorbed CH4. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Catalytic Materials)
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7 pages, 1884 KiB  
Communication
Three-Dimensional Epitaxy of Low-Defect 3C-SiC on a Geometrically Modified Silicon Substrate
by Gerard Colston, Kelly Turner, Arne Renz, Kushani Perera, Peter M. Gammon, Marina Antoniou and Vishal A. Shah
Materials 2024, 17(7), 1587; https://doi.org/10.3390/ma17071587 - 30 Mar 2024
Viewed by 644
Abstract
We demonstrate the growth of 3C-SiC with reduced planar defects on a micro-scale compliant substrate. Heteroepitaxial growth of 3C-SiC on trenches with a width and separation of 2 µm, etched into a Si(001) substrate, is found to suppress defect propagation through the epilayer. [...] Read more.
We demonstrate the growth of 3C-SiC with reduced planar defects on a micro-scale compliant substrate. Heteroepitaxial growth of 3C-SiC on trenches with a width and separation of 2 µm, etched into a Si(001) substrate, is found to suppress defect propagation through the epilayer. Stacking faults and other planar defects are channeled away from the center of the patterned structures, which are rounded through the use of H2 annealing at 1100 °C. Void formation between the columns of 3C-SiC growth acts as a termination point for defects, and coalescence of these columns into a continuous epilayer is promoted through the addition of HCl in the growth phase. The process of fabricating these compliant substrates utilizes standard processing techniques found within the semiconductor industry and is independent of the substrate orientation and offcut. Full article
(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)
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15 pages, 6948 KiB  
Article
Enhancement of Strength–Ductility Synergy of Al-Li Cast Alloy via New Forming Processes and Sc Addition
by Shulin Lü, Zhaoxiang Yan, Yu Pan, Jianyu Li, Shusen Wu and Wei Guo
Materials 2024, 17(7), 1558; https://doi.org/10.3390/ma17071558 - 28 Mar 2024
Viewed by 688
Abstract
In this study, concurrent enhancements in both strength and ductility of the Al-2Li-2Cu-0.5Mg-0.2Zr cast alloy (hereafter referred to as Al-Li) were achieved through an optimized forming process comprising ultrasonic treatment followed by squeeze casting, coupled with the incorporation of Sc. Initially, the variations [...] Read more.
In this study, concurrent enhancements in both strength and ductility of the Al-2Li-2Cu-0.5Mg-0.2Zr cast alloy (hereafter referred to as Al-Li) were achieved through an optimized forming process comprising ultrasonic treatment followed by squeeze casting, coupled with the incorporation of Sc. Initially, the variations in the microstructure and mechanical properties of the Sc-free Al-Li cast alloy (i.e., alloy A) during various forming processes were investigated. The results revealed that the grain size in the UT+SC (ultrasonic treatment + squeeze casting) alloy was reduced by 76.3% and 57.7%, respectively, compared to those of the GC (gravity casting) or SC alloys. Additionally, significant improvements were observed in its compositional segregation and porosity reduction. After UT+SC, the ultimate tensile strength (UTS), yield strength (YS), and elongation reached 235 MPa, 135 MPa, and 15%, respectively, which were 113.6%, 28.6%, and 1150% higher than those of the GC alloy. Subsequently, the Al-Li cast alloy containing 0.2 wt.% Sc (referred to as alloy B) exhibited even finer grains under the UT+SC process, resulting in simultaneous enhancements in its UTS, YS, and elongation. Interestingly, the product of ultimate tensile strength and elongation (i.e., UTS × EL) for both alloys reached 36 GPa•% and 42 GPa•%, respectively, which is much higher than that of other Al-Li cast alloys reported in the available literature. Full article
(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)
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15 pages, 6758 KiB  
Article
Modeling of Charge-to-Breakdown with an Electron Trapping Model for Analysis of Thermal Gate Oxide Failure Mechanism in SiC Power MOSFETs
by Jiashu Qian, Limeng Shi, Michael Jin, Monikuntala Bhattacharya, Atsushi Shimbori, Hengyu Yu, Shiva Houshmand, Marvin H. White and Anant K. Agarwal
Materials 2024, 17(7), 1455; https://doi.org/10.3390/ma17071455 - 22 Mar 2024
Viewed by 828
Abstract
The failure mechanism of thermal gate oxide in silicon carbide (SiC) power metal oxide semiconductor field effect transistors (MOSFETs), whether it is field-driven breakdown or charge-driven breakdown, has always been a controversial topic. Previous studies have demonstrated that the failure time of thermally [...] Read more.
The failure mechanism of thermal gate oxide in silicon carbide (SiC) power metal oxide semiconductor field effect transistors (MOSFETs), whether it is field-driven breakdown or charge-driven breakdown, has always been a controversial topic. Previous studies have demonstrated that the failure time of thermally grown silicon dioxide (SiO2) on SiC stressed with a constant voltage is indicated as charge driven rather than field driven through the observation of Weibull Slope β. Considering the importance of the accurate failure mechanism for the thermal gate oxide lifetime prediction model of time-dependent dielectric breakdown (TDDB), charge-driven breakdown needs to be further fundamentally justified. In this work, the charge-to-breakdown (QBD) of the thermal gate oxide in a type of commercial planar SiC power MOSFETs, under the constant current stress (CCS), constant voltage stress (CVS), and pulsed voltage stress (PVS) are extracted, respectively. A mathematical electron trapping model in thermal SiO2 grown on single crystal silicon (Si) under CCS, which was proposed by M. Liang et al., is proven to work equally well with thermal SiO2 grown on SiC and used to deduce the QBD model of the device under test (DUT). Compared with the QBD obtained under the three stress conditions, the charge-driven breakdown mechanism is validated in the thermal gate oxide of SiC power MOSFETs. Full article
(This article belongs to the Special Issue Silicon Carbide: Material Growth, Device Processing and Applications)
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14 pages, 6419 KiB  
Article
Tailoring Iridium Valence States on ZSM-5 for Enhanced Catalytic Performance in CO Selective Catalytic Reduction of NO under Oxygen-Enriched Environments
by Yarong Bai, Chuhan Miao, Weilong Ouyang, Lang Wang, Haiqiang Wang and Zhongbiao Wu
Materials 2024, 17(6), 1440; https://doi.org/10.3390/ma17061440 - 21 Mar 2024
Viewed by 653
Abstract
Barium and iridium supported on Zeolite Socony Mobil-5 (ZSM-5) are efficient catalysts for the selective catalytic reduction of nitric oxide by carbon monoxide (CO-SCR), with enhanced cyclic stability. The introduction of Ba hindered the oxidation of metallic Ir active species and enabled Ir [...] Read more.
Barium and iridium supported on Zeolite Socony Mobil-5 (ZSM-5) are efficient catalysts for the selective catalytic reduction of nitric oxide by carbon monoxide (CO-SCR), with enhanced cyclic stability. The introduction of Ba hindered the oxidation of metallic Ir active species and enabled Ir to maintain an active metallic state, thereby preventing a decrease in catalytic activity in the CO-SCR reaction. Moreover, the Ba modification increased the NO adsorption of the catalyst, further improving the catalytic activity. Owing to the better anti-oxidation ability of Ir0 in IrBa0.2/ZSM-5(27) than in Ir/ZSM-5(27), IrBa0.2/ZSM-5(27) showed better stability than Ir/ZSM-5(27). Considering that all samples in the present study were tested to simulate actual flue gases (such as sintering flue gas and coke oven flue gas), NH3 was introduced into the reaction system to serve as an extra reductant for NOx. The NOx conversion to N2 (77.1%) was substantially improved using the NH3-CO-SCR system. The proposed catalysts and reaction systems are promising alternatives for treating flue gas, which contains considerable amounts of NOx and CO in oxygen-enriched environments. Full article
(This article belongs to the Section Catalytic Materials)
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12 pages, 8092 KiB  
Article
A Study of the Adsorption Properties of Individual Atoms on the Graphene Surface: Density Functional Theory Calculations Assisted by Machine Learning Techniques
by Jingtao Huang, Mo Chen, Jingteng Xue, Mingwei Li, Yuan Cheng, Zhonghong Lai, Jin Hu, Fei Zhou, Nan Qu, Yong Liu and Jingchuan Zhu
Materials 2024, 17(6), 1428; https://doi.org/10.3390/ma17061428 - 20 Mar 2024
Viewed by 738
Abstract
In this research, the adsorption performance of individual atoms on the surface of monolayer graphene surface was systematically investigated using machine learning methods to accelerate density functional theory. The adsorption behaviors of over thirty different atoms on the graphene surface were computationally analyzed. [...] Read more.
In this research, the adsorption performance of individual atoms on the surface of monolayer graphene surface was systematically investigated using machine learning methods to accelerate density functional theory. The adsorption behaviors of over thirty different atoms on the graphene surface were computationally analyzed. The adsorption energy and distance were extracted as the research targets, and the basic information of atoms (such as atomic radius, ionic radius, etc.) were used as the feature values to establish the dataset. Through feature engineering selection, the corresponding input feature values for the input-output relationship were determined. By comparing different models on the dataset using five-fold cross-validation, the mathematical model that best fits the dataset was identified. The optimal model was further fine-tuned by adjusting of the best mathematical ML model. Subsequently, we verified the accuracy of the established machine learning model. Finally, the precision of the machine learning model forecasts was verified by the method of comparing and contrasting machine learning results with density functional theory. The results suggest that elements such as Zr, Ti, Sc, and Si possess some potential in controlling the interfacial reaction of graphene/aluminum composites. By using machine learning to accelerate first-principles calculations, we have further expanded our choice of research methods and accelerated the pace of studying element–graphene interactions. Full article
(This article belongs to the Special Issue Adsorption Materials and Their Applications)
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23 pages, 30993 KiB  
Article
Numerical Simulation and Machine Learning Prediction of the Direct Chill Casting Process of Large-Scale Aluminum Ingots
by Guanhua Guo, Ting Yao, Wensheng Liu, Sai Tang, Daihong Xiao, Lanping Huang, Lei Wu, Zhaohui Feng and Xiaobing Gao
Materials 2024, 17(6), 1409; https://doi.org/10.3390/ma17061409 - 19 Mar 2024
Viewed by 916
Abstract
The large-scale ingot of the 7xxx-series aluminum alloys fabricated by direct chill (DC) casting often suffers from foundry defects such as cracks and cold shut due to the formidable challenges in the precise controlling of casting parameters. In this manuscript, by using the [...] Read more.
The large-scale ingot of the 7xxx-series aluminum alloys fabricated by direct chill (DC) casting often suffers from foundry defects such as cracks and cold shut due to the formidable challenges in the precise controlling of casting parameters. In this manuscript, by using the integrated computational method combining numerical simulations with machine learning, we systematically estimated the evolution of multi-physical fields and grain structures during the solidification processes. The numerical simulation results quantified the influences of key casting parameters including pouring temperature, casting speed, primary cooling intensity, and secondary cooling water flow rate on the shape of the mushy zone, heat transport, residual stress, and grain structure of DC casting ingots. Then, based on the data of numerical simulations, we established a novel model for the relationship between casting parameters and solidification characteristics through machine learning. By comparing it with experimental measurements, the model showed reasonable accuracy in predicting the sump profile, microstructure evolution, and solidification kinetics under the complicated influences of casting parameters. The integrated computational method and predicting model could be used to efficiently and accurately determine the DC casting parameters to decrease the casting defects. Full article
(This article belongs to the Section Metals and Alloys)
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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 853
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
(This article belongs to the Special Issue Synthesis, Modeling, Physico-Chemical and Biological Properties of Metal Complexes)
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23 pages, 15469 KiB  
Article
Interfacial Segregation of Sn during the Continuous Annealing and Selective Oxidation of Fe-Mn-Sn Alloys
by Jonas Wagner and Joseph R. McDermid
Materials 2024, 17(6), 1257; https://doi.org/10.3390/ma17061257 - 8 Mar 2024
Cited by 1 | Viewed by 609
Abstract
The effect of Mn on interfacial Sn segregation during the selective oxidation of Fe-(0–10)Mn-0.03Sn (at.%) alloys was determined for annealing conditions compatible with continuous galvanizing. Significant Sn enrichment was observed at the substrate free surface and metal/oxide interface for all annealing conditions and [...] Read more.
The effect of Mn on interfacial Sn segregation during the selective oxidation of Fe-(0–10)Mn-0.03Sn (at.%) alloys was determined for annealing conditions compatible with continuous galvanizing. Significant Sn enrichment was observed at the substrate free surface and metal/oxide interface for all annealing conditions and Mn levels. Sn enrichment at the free surface was insensitive to the Mn alloy concentration, which was partially attributed to the opposing effects of Mn on segregation thermodynamics and kinetics: Mn increases the driving force for Sn segregation via reducing Sn solubility in Fe but also reduces the effective Sn diffusivity by increasing the austenite volume fraction. This insensitivity was exacerbated by the depletion of solute Mn near the surface due to the selective oxidation of Mn. Thus, Sn segregation occurred in regions with a local Mn concentration lower than the nominal bulk composition of the alloys suggested. Sn enrichment at the metal/external oxide interface was reduced compared to the free surface and decreased with increasing bulk Mn content, which was attributed to changes in the external oxide morphology and metal/internal oxide interfaces acting as Sn sinks. Full article
(This article belongs to the Section Metals and Alloys)
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20 pages, 7712 KiB  
Article
The Influence of the Shielding-Gas Flow Rate on the Mechanical Properties of TIG-Welded Butt Joints of Commercially Pure Grade 1 Titanium
by Krzysztof Szwajka, Joanna Zielińska-Szwajka and Tomasz Trzepieciński
Materials 2024, 17(5), 1217; https://doi.org/10.3390/ma17051217 - 6 Mar 2024
Viewed by 734
Abstract
This article proposes as a novelty the differentiation of shielding-gas flow rates from both sides of the tungsten inert gas (TIG)-welded butt joints of commercially pure (CP) grade 1 titanium tubes. Such an approach is aimed at economically reducing the amount of protective [...] Read more.
This article proposes as a novelty the differentiation of shielding-gas flow rates from both sides of the tungsten inert gas (TIG)-welded butt joints of commercially pure (CP) grade 1 titanium tubes. Such an approach is aimed at economically reducing the amount of protective gas used in TIG closed butt welding. The effect of the shielding-gas flow rate on the properties of CP grade 1 titanium butt-welded joints made using the tungsten inert gas (TIG)-welding method. Butt-welded joints were made for different values of the shielding-gas flow from the side of the root of the weld. Argon 5.0 was used as the shielding gas in the welding process. As part of the research, the welded joints obtained were analysed using optical and scanning electron microscopy. The microstructural characteristics of the joints were examined using an optical microscope, and the mechanical properties were determined using hardness and tensile tests. It was observed that as the flow of the shielding gas decreases, the hardness of the weld material increases and its brittleness also increases. A similar trend related to the amount of gas flow was also noticeable for the tensile strength of the joints. The increase in the hardness of the weld and the heat-affected zone compared to the base metal is mainly related to the increase in the amount of acicular structure (α′ phase). The optimal gas flow rates from the side of the root of weld were found at the values of 12 dm3/min. Full article
(This article belongs to the Special Issue Advances in Welding Techniques, Welding Inspection, and Welding Testing Methods)
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45 pages, 11151 KiB  
Review
Evaluation of the Embrittlement in Reactor Pressure-Vessel Steels Using a Hybrid Nondestructive Electromagnetic Testing and Evaluation Approach
by Gábor Vértesy, Madalina Rabung, Antal Gasparics, Inge Uytdenhouwen, James Griffin, Daniel Algernon, Sonja Grönroos and Jari Rinta-Aho
Materials 2024, 17(5), 1106; https://doi.org/10.3390/ma17051106 - 28 Feb 2024
Viewed by 924
Abstract
The nondestructive determination of the neutron-irradiation-induced embrittlement of nuclear reactor pressure-vessel steel is a very important and recent problem. Within the scope of the so-called NOMAD project funded by the Euratom research and training program, novel nondestructive electromagnetic testing and evaluation (NDE) methods [...] Read more.
The nondestructive determination of the neutron-irradiation-induced embrittlement of nuclear reactor pressure-vessel steel is a very important and recent problem. Within the scope of the so-called NOMAD project funded by the Euratom research and training program, novel nondestructive electromagnetic testing and evaluation (NDE) methods were applied to the inspection of irradiated reactor pressure-vessel steel. In this review, the most important results of this project are summarized. Different methods were used and compared with each other. The measurement results were compared with the destructively determined ductile-to-brittle transition temperature (DBTT) values. Three magnetic methods, 3MA (micromagnetic, multiparameter, microstructure and stress analysis), MAT (magnetic adaptive testing), and Barkhausen noise technique (MBN), were found to be the most promising techniques. The results of these methods were in good agreement with each other. A good correlation was found between the magnetic parameters and the DBTT values. The basic idea of the NOMAD project is to use a multi-method/multi-parameter approach and to focus on the synergies that allow us to recognize the side effects, therefore suppressing them at the same time. Different types of machine-learning (ML) algorithms were tested in a competitive manner, and their performances were evaluated. The important outcome of the ML technique is that not only one but several different ML techniques could reach the required precision and reliability, i.e., keeping the DBTT prediction error lower than a ±25 °C threshold, which was previously not possible for any of the NDE methods as single entities. A calibration/training procedure was carried out on the merged outcome of the testing methods with excellent results to predict the transition temperature, yield strength, and mechanical hardness for all investigated materials. Our results, achieved within the NOMAD project, can be useful for the future potential introduction of this (and, in general, any) nondestructive evolution method. Full article
(This article belongs to the Section Materials Physics)
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24 pages, 9586 KiB  
Article
The Development of Sustainable Polyethylene Terephthalate Glycol-Based (PETG) Blends for Additive Manufacturing Processing—The Use of Multilayered Foil Waste as the Blend Component
by Mikołaj Garwacki, Igor Cudnik, Damian Dziadowiec, Piotr Szymczak and Jacek Andrzejewski
Materials 2024, 17(5), 1083; https://doi.org/10.3390/ma17051083 - 27 Feb 2024
Viewed by 1339
Abstract
The polymer foil industry is one of the leading producers of plastic waste. The development of new recycling methods for packaging products is one of the biggest demands in today’s engineering. The subject of this research was the melt processing of multilayered PET-based [...] Read more.
The polymer foil industry is one of the leading producers of plastic waste. The development of new recycling methods for packaging products is one of the biggest demands in today’s engineering. The subject of this research was the melt processing of multilayered PET-based foil waste with PETG copolymer. The resulting blends were intended for additive manufacturing processing using the fused deposition modeling (FDM) method. In order to improve the properties of the developed materials, the blends compounding procedure was conducted with the addition of a reactive chain extender (CE) and elastomeric copolymer used as an impact modifier (IM). The samples were manufactured using the 3D printing technique and, for comparison, using the traditional injection molding method. The obtained samples were subjected to a detailed characterization procedure, including mechanical performance evaluation, thermal analysis, and rheological measurements. This research confirms that PET-based film waste can be successfully used for the production of filament, and for most samples, the FDM printing process can be conducted without any difficulties. Unfortunately, the unmodified blends are characterized by brittleness, which makes it necessary to use an elastomer additive (IM). The presence of a semicrystalline PET phase improves the thermal resistance of the prepared blends; however, an annealing procedure is required for this purpose. Full article
(This article belongs to the Special Issue Polymers: From Waste to Potential Reuse)
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32 pages, 5942 KiB  
Article
An Extended Kolmogorov–Avrami–Ishibashi (EKAI) Model to Simulate Dynamic Characteristics of Polycrystalline-Ferroelectric-Gate Field-Effect Transistors
by Shigeki Sakai and Mitsue Takahashi
Materials 2024, 17(5), 1077; https://doi.org/10.3390/ma17051077 - 26 Feb 2024
Viewed by 1345
Abstract
A physics-based model on polarization switching in ferroelectric polycrystalline films is proposed. The calculation results by the model agree well with experimental results regarding dynamic operations of ferroelectric-gate field-effect transistors (FeFETs). In the model, an angle θ for each grain in the ferroelectric [...] Read more.
A physics-based model on polarization switching in ferroelectric polycrystalline films is proposed. The calculation results by the model agree well with experimental results regarding dynamic operations of ferroelectric-gate field-effect transistors (FeFETs). In the model, an angle θ for each grain in the ferroelectric polycrystal is defined, where θ is the angle between the spontaneous polarization and the film normal direction. Under a constant electric field for a single-crystal film with θ = 0, phenomena regarding polarization domain nucleation and wall propagation are well described by the Kolmogorov–Avrami–Ishibashi theory. Since the electric fields are time-dependent in FeFET operations and the θ values are distributed in the polycrystalline film, the model in this paper forms an extended Kolmogorov–Avrami–Ishibashi (EKAI) model. Under a low electric field, the nucleation and domain propagation proceed according to thermally activated processes, meaning that switching the time scale of a grain with the angle θ is proportional to an exponential form as exp(const./Ezcosθ) [Ez: the film-normal electric field]. Wide θ distribution makes the time response quite broad even on the logarithmic scale, which relates well with the broad switching time experimentally shown by FeFETs. The EKAI model is physics based and need not assume non-physical distribution functions in it. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Materials Physics)
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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
Cited by 1 | Viewed by 1002
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
(This article belongs to the Special Issue Size-Dependent Effects in Materials for Environmental Protection and Energy Application)
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44 pages, 14513 KiB  
Review
Hydrogen Impact: A Review on Diffusibility, Embrittlement Mechanisms, and Characterization
by Qidong Li, Hesamedin Ghadiani, Vahid Jalilvand, Tahrim Alam, Zoheir Farhat and Md. Aminul Islam
Materials 2024, 17(4), 965; https://doi.org/10.3390/ma17040965 - 19 Feb 2024
Cited by 6 | Viewed by 2222
Abstract
Hydrogen embrittlement (HE) is a broadly recognized phenomenon in metallic materials. If not well understood and managed, HE may lead to catastrophic environmental failures in vessels containing hydrogen, such as pipelines and storage tanks. HE can affect the mechanical properties of materials such [...] Read more.
Hydrogen embrittlement (HE) is a broadly recognized phenomenon in metallic materials. If not well understood and managed, HE may lead to catastrophic environmental failures in vessels containing hydrogen, such as pipelines and storage tanks. HE can affect the mechanical properties of materials such as ductility, toughness, and strength, mainly through the interaction between metal defects and hydrogen. Various phenomena such as hydrogen adsorption, hydrogen diffusion, and hydrogen interactions with intrinsic trapping sites like dislocations, voids, grain boundaries, and oxide/matrix interfaces are involved in this process. It is important to understand HE mechanisms to develop effective hydrogen resistant strategies. Tensile, double cantilever beam, bent beam, and fatigue tests are among the most common techniques employed to study HE. This article reviews hydrogen diffusion behavior, mechanisms, and characterization techniques. Full article
(This article belongs to the Special Issue Corrosion and Mechanical Behavior of Metal Materials (2nd Edition))
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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 2293
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
(This article belongs to the Special Issue Materials Nanoarchitectonics for Membranes, Surfaces, Self-Assembly, and Biomimetics)
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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
Cited by 1 | Viewed by 604
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 - 9 Feb 2024
Viewed by 923
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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16 pages, 5925 KiB  
Article
Microstructure and Mechanical Properties of Ti-6Al-4V Welds Produced with Different Processes
by Sakari Tolvanen, Robert Pederson and Uta Klement
Materials 2024, 17(4), 782; https://doi.org/10.3390/ma17040782 - 6 Feb 2024
Viewed by 733
Abstract
The effect of defects and microstructure on the mechanical properties of Ti-6Al-4V welds produced by tungsten inert gas welding; plasma arc welding; electron beam welding; and laser beam welding was studied in the present work. The mechanical properties of different weld types were [...] Read more.
The effect of defects and microstructure on the mechanical properties of Ti-6Al-4V welds produced by tungsten inert gas welding; plasma arc welding; electron beam welding; and laser beam welding was studied in the present work. The mechanical properties of different weld types were evaluated with respect to micro hardness; yield strength; ultimate tensile strength; ductility; and fatigue at room temperature and at elevated temperatures (200 °C and 250 °C). Metallographic investigation was carried out to characterize the microstructures of different weld types, and fractographic investigation was conducted to relate the effect of defects on fatigue performance. Electron and laser beam welding produced welds with finer microstructure, higher tensile ductility, and better fatigue performance than tungsten inert gas welding and plasma arc welding. Large pores, and pores located close to the specimen surface, were found to be most detrimental to fatigue life. Full article
(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys)
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24 pages, 6651 KiB  
Article
Application of Activated Carbons Obtained from Polymer Waste for the Adsorption of Dyes from Aqueous Solutions
by Katarzyna Jedynak and Barbara Charmas
Materials 2024, 17(3), 748; https://doi.org/10.3390/ma17030748 - 4 Feb 2024
Cited by 2 | Viewed by 833
Abstract
Plastic waste disposal is a major environmental problem worldwide. One recycling method for polymeric materials is their conversion into carbon materials. Therefore, a process of obtaining activated carbons through the carbonization of waste CDs (as the selected carbon precursor) in an oxygen-free atmosphere, [...] Read more.
Plastic waste disposal is a major environmental problem worldwide. One recycling method for polymeric materials is their conversion into carbon materials. Therefore, a process of obtaining activated carbons through the carbonization of waste CDs (as the selected carbon precursor) in an oxygen-free atmosphere, and then the physical activation of the obtained material with CO2, was developed. Dyes such as methylene blue (MB) and malachite green (MG) are commonly applied in industry, which contaminate the water environment to a large extent and have a harmful effect on living organisms; therefore, adsorption studies were carried out for these cationic dyes. The effects of the activation time on the physicochemical properties of the activated materials and the adsorption capacity of the dyes were investigated. The obtained microporous adsorbents were characterized by studying the porous structure based on low-temperature nitrogen adsorption/desorption, scanning electron microscopy (SEM-EDS), elemental analysis (CHNS), Raman spectroscopy, X-ray powder diffraction (XRD), infrared spectroscopy (ATR FT-IR), thermal analysis (TG, DTG, DTA), Boehm’s titration method, and pHpzc (the point of zero charge) determination. Moreover, adsorption studies (equilibrium and kinetics) were carried out. The maximum adsorption capacities (qm exp) of MB and MG (349 mg g−1 and 274 mg g−1, respectively) were identified for the obtained material after 8 h of activation. The results show that the use of waste CDs as a carbon precursor facilitates the production of low-cost and effective adsorbents. Full article
(This article belongs to the Special Issue Applications of Polymer Materials: Adsorption, Catalysis, and Degradation)
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16 pages, 10559 KiB  
Article
Mechanical Characterization of Multifunctional Metal-Coated Polymer Lattice Structures
by Lizhe Wang, Liu He, Fuyuan Liu, Hang Yuan, Ji Li and Min Chen
Materials 2024, 17(3), 741; https://doi.org/10.3390/ma17030741 - 3 Feb 2024
Cited by 2 | Viewed by 1242
Abstract
Metal-coated lattice structures hold significant promise for customizing mechanical properties in diverse industrial applications, including the mechanical arms of unmanned aerial vehicles. However, their intricate geometries pose computational challenges, resulting in time-intensive and costly numerical evaluations. This study introduces a parameterization-based multiscale method [...] Read more.
Metal-coated lattice structures hold significant promise for customizing mechanical properties in diverse industrial applications, including the mechanical arms of unmanned aerial vehicles. However, their intricate geometries pose computational challenges, resulting in time-intensive and costly numerical evaluations. This study introduces a parameterization-based multiscale method to analyze body-centered cubic lattice structures with metal coatings. We establish the validity and precision of our proposed method with a comparative analysis of numerical results at the Representative Volume Element (RVE) scale and experimental findings, specifically addressing both elastic tensile and bending stiffness. Furthermore, we showcase the method’s accuracy in interpreting the bending stiffness of coated lattice structures using a homogenized material-based solid model, underscoring its effectiveness in predicting the elastic properties of such structures. In exploring the mechanical characterization of coated lattice structures, we unveil positive correlations between elastic tensile stiffness and both coating thickness and strut diameter. Additionally, the metal coating significantly enhances the structural elastic bending stiffness multiple times over. The diverse failure patterns observed in coated lattices under tensile and bending loads primarily stem from varied loading-induced stress states rather than external factors. This work not only mitigates computational challenges but also successfully bridges the gap between mesoscale RVE mechanical properties and those at the global structural scale. Full article
(This article belongs to the Section Porous Materials)
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14 pages, 3622 KiB  
Article
Flexible Dry Electrode Based on a Wrinkled Surface That Uses Carbon Nanotube/Polymer Composites for Recording Electroencephalograms
by Jihyeon Oh, Kun-Woo Nam, Won-Jin Kim, Byung-Ho Kang and Sung-Hoon Park
Materials 2024, 17(3), 668; https://doi.org/10.3390/ma17030668 - 30 Jan 2024
Viewed by 1154
Abstract
Electroencephalography (EEG) captures minute electrical signals emanating from the brain. These signals are vulnerable to interference from external noise and dynamic artifacts; hence, accurately recording such signals is challenging. Although dry electrodes are convenient, their signals are of limited quality; consequently, wet electrodes [...] Read more.
Electroencephalography (EEG) captures minute electrical signals emanating from the brain. These signals are vulnerable to interference from external noise and dynamic artifacts; hence, accurately recording such signals is challenging. Although dry electrodes are convenient, their signals are of limited quality; consequently, wet electrodes are predominantly used in EEG. Therefore, developing dry electrodes for accurately and stably recording EEG signals is crucial. In this study, we developed flexible dry electrodes using polydimethylsiloxane (PDMS)/carbon-nanotube (CNT) composites with isotropically wrinkled surfaces that effectively combine the advantages of wet and dry electrodes. Adjusting the PDMS crosslinker ratio led to good adhesion, resulting in a highly adhesive CNT/PDMS composite with a low Young’s modulus that exhibited excellent electrical and mechanical properties owing to its ability to conformally contact skin. The isotropically wrinkled surface also effectively controls dynamic artifacts during EEG signal detection and ensures accurate signal analysis. The results of this study demonstrate that dry electrodes based on flexible CNT/PDMS composites and corrugated structures can outperform wet electrodes. The introduction of such electrodes is expected to enable the accurate analysis and monitoring of EEG signals in various scenarios, including clinical trials. Full article
(This article belongs to the Special Issue Preparation, Processing, and Application of Advanced Functional Carbon Materials)
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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 843
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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19 pages, 37911 KiB  
Article
Near Net Shape Manufacturing of Sheets from Al-Cu-Li-Mg-Sc-Zr Alloy
by Barbora Kihoulou, Rostislav Králík, Lucia Bajtošová, Olexandr Grydin, Mykhailo Stolbchenko, Mirko Schaper and Miroslav Cieslar
Materials 2024, 17(3), 644; https://doi.org/10.3390/ma17030644 - 28 Jan 2024
Cited by 1 | Viewed by 783
Abstract
Thin twin-roll cast strips from a model Al-Cu-Mg-Li-Zr alloy with a small addition of Sc were prepared. A combination of a fast solidification rate and a favorable effect of Sc microalloying refines the grain size and the size of primary phase particles and [...] Read more.
Thin twin-roll cast strips from a model Al-Cu-Mg-Li-Zr alloy with a small addition of Sc were prepared. A combination of a fast solidification rate and a favorable effect of Sc microalloying refines the grain size and the size of primary phase particles and reduces eutectic cell dimensions to 10–15 μm. Long-term homogenization annealings used in conventionally cast materials lasting several tens of hours followed by a necessary dimension reduction through rolling/extruding could be substituted by energy and material-saving procedure. It consists of two-step short annealings at 300 °C/30 min and 450 °C/30 min, followed by the refinement and hardening of the structure using constrained groove pressing. A dense dispersion of 10–20 nm spherical Al3(Sc,Zr) precipitates intensively forms during this treatment and effectively stabilizes the structure and inhibits the grain growth during subsequent solution treatment at 530 °C/30 min. Small (3%) pre-straining after quenching assures more uniform precipitation of strengthening Al2Cu (θ′), Al2CuMg (S′), and Al2CuLi (T1) particles during subsequent age-hardening annealing at 180 °C/14 h. The material does not contain a directional and anisotropic structure unavoidable in rolled or extruded sheets. The proposed procedure thus represents a model near net shape processing strategy for manufacturing lightweight high-strength sheets for cryogenic applications in aeronautics. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Materials Physics)
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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 786
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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11 pages, 1786 KiB  
Article
Rapid Plasma Electrolytic Oxidation Synthesis of Intermetallic PtBi/MgO/Mg Monolithic Catalyst for Efficient Removal of Organic Pollutants
by Jiayi Rong, Mengyang Li, Feng Cao, Qianwei Wang, Mingran Wang, Yang Cao, Jun Zhou and Gaowu Qin
Materials 2024, 17(3), 605; https://doi.org/10.3390/ma17030605 - 26 Jan 2024
Viewed by 656
Abstract
The intermetallic PtBi/MgO/Mg monolithic catalyst was first prepared using non-equilibrium plasma electrolytic oxidation (PEO) technology. Spherical aberration-corrected transmission electron microscope (ACTEM) observation confirms the successful synthesis of the PtBi intermetallic structure. The efficiency of PtBi/Mg/MgO catalysts in catalyzing the reduction of 4-nitrophenol (4-NP) [...] Read more.
The intermetallic PtBi/MgO/Mg monolithic catalyst was first prepared using non-equilibrium plasma electrolytic oxidation (PEO) technology. Spherical aberration-corrected transmission electron microscope (ACTEM) observation confirms the successful synthesis of the PtBi intermetallic structure. The efficiency of PtBi/Mg/MgO catalysts in catalyzing the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4 was demonstrated. The activity factor for the catalyst is 31.8 s−1 g−1, which is much higher than reported values. In addition, the resultant catalyst also exhibits excellent catalytic activity in the organic pollutant reaction of p-nitrobenzoic acid (p-NBA) and methyl orange (MO). Moreover, benefiting from ordered atomic structures and the half-embedded PtBi nanoparticles (NPs), the catalyst demonstrates excellent stability and reproducibility in the degradation of 4-NP. This study provides an example of a simple method for the preparation of intermetallic structures as catalysts for organic pollutant degradation. Full article
(This article belongs to the Special Issue Advances in Multicomponent Catalytic Materials)
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78 pages, 27700 KiB  
Review
Cryogenic Treatment of Martensitic Steels: Microstructural Fundamentals and Implications for Mechanical Properties and Wear and Corrosion Performance
by Peter Jurči and Ivo Dlouhý
Materials 2024, 17(3), 548; https://doi.org/10.3390/ma17030548 - 23 Jan 2024
Cited by 3 | Viewed by 1112
Abstract
Conventional heat treatment is not capable of converting a sufficient amount of retained austenite into martensite in high-carbon or high-carbon and high-alloyed iron alloys. Cryogenic treatment induces the following alterations in the microstructures: (i) a considerable reduction in the retained austenite amount, (ii) [...] Read more.
Conventional heat treatment is not capable of converting a sufficient amount of retained austenite into martensite in high-carbon or high-carbon and high-alloyed iron alloys. Cryogenic treatment induces the following alterations in the microstructures: (i) a considerable reduction in the retained austenite amount, (ii) formation of refined martensite coupled with an increased number of lattice defects, such as dislocations and twins, (iii) changes in the precipitation kinetics of nano-sized transient carbides during tempering, and (iv) an increase in the number of small globular carbides. These microstructural alterations are reflected in mechanical property improvements and better dimensional stability. A common consequence of cryogenic treatment is a significant increase in the wear resistance of steels. The current review deals with all of the mentioned microstructural changes as well as the variations in strength, toughness, wear performance, and corrosion resistance for a variety of iron alloys, such as carburising steels, hot work tool steels, bearing and eutectoid steels, and high-carbon and high-alloyed ledeburitic cold work tool steels. Full article
(This article belongs to the Special Issue Physical Metallurgy of Metals and Alloys II)
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13 pages, 2282 KiB  
Article
Structural and Photoelectronic Properties of κ-Ga2O3 Thin Films Grown on Polycrystalline Diamond Substrates
by Marco Girolami, Matteo Bosi, Sara Pettinato, Claudio Ferrari, Riccardo Lolli, Luca Seravalli, Valerio Serpente, Matteo Mastellone, Daniele M. Trucchi and Roberto Fornari
Materials 2024, 17(2), 519; https://doi.org/10.3390/ma17020519 - 22 Jan 2024
Cited by 1 | Viewed by 1022
Abstract
Orthorhombic κ-Ga2O3 thin films were grown for the first time on polycrystalline diamond free-standing substrates by metal-organic vapor phase epitaxy at a temperature of 650 °C. Structural, morphological, electrical, and photoelectronic properties of the obtained heterostructures were evaluated by optical [...] Read more.
Orthorhombic κ-Ga2O3 thin films were grown for the first time on polycrystalline diamond free-standing substrates by metal-organic vapor phase epitaxy at a temperature of 650 °C. Structural, morphological, electrical, and photoelectronic properties of the obtained heterostructures were evaluated by optical microscopy, X-ray diffraction, current-voltage measurements, and spectral photoconductivity, respectively. Results show that a very slow cooling, performed at low pressure (100 mbar) under a controlled He flow soon after the growth process, is mandatory to improve the quality of the κ-Ga2O3 epitaxial thin film, ensuring a good adhesion to the diamond substrate, an optimal morphology, and a lower density of electrically active defects. This paves the way for the future development of novel hybrid architectures for UV and ionizing radiation detection, exploiting the unique features of gallium oxide and diamond as wide-bandgap semiconductors. Full article
(This article belongs to the Special Issue Thin Films and Semiconductor Heterostructures: From Fundamental to Applications)
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12 pages, 4522 KiB  
Article
Impact of Glass Free Volume on Femtosecond Laser-Written Nanograting Formation in Silica Glass
by Nadezhda Shchedrina, Maxime Cavillon, Julien Ari, Nadège Ollier and Matthieu Lancry
Materials 2024, 17(2), 502; https://doi.org/10.3390/ma17020502 - 20 Jan 2024
Cited by 1 | Viewed by 785
Abstract
In this study, we investigate the effects of densification through high pressure and temperature (up to 5 GPa, 1000 °C) in the making of nanogratings in pure silica glass, inscribed with femtosecond laser. The latter were monitored through retardance measurements using polarized optical [...] Read more.
In this study, we investigate the effects of densification through high pressure and temperature (up to 5 GPa, 1000 °C) in the making of nanogratings in pure silica glass, inscribed with femtosecond laser. The latter were monitored through retardance measurements using polarized optical microscopy, and their internal structure was observed under scanning electron microscopy. We reveal the difficulty in making nanogratings in densified silica glasses. Based on this observation, we propose that free volume may be a key precursor to initiate nanograting formation. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Materials Physics)
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18 pages, 24962 KiB  
Article
Feasibility Study on the Generation of Nanoporous Metal Structures by Means of Selective Alloy Depletion in Halogen-Rich Atmospheres
by Jörg Weise, Birgit Uhrlaub, Dirk Lehmhus, Joachim Baumeister, Kerstin Hantzsche and Karsten Thiel
Materials 2024, 17(2), 498; https://doi.org/10.3390/ma17020498 - 20 Jan 2024
Viewed by 673
Abstract
A new approach to produce nanoporous metals has been investigated, which is based on the dealloying of bi- or multi-component alloys. Depletion and pore formation of the alloy substrate are obtained by the transport of certain alloy components at high temperatures via volatile [...] Read more.
A new approach to produce nanoporous metals has been investigated, which is based on the dealloying of bi- or multi-component alloys. Depletion and pore formation of the alloy substrate are obtained by the transport of certain alloy components at high temperatures via volatile halogen compounds. These halogen compounds are transferred to materials acting as sinks based on their higher affinity to the respective components, and chemically bound there. Transfer via volatile halogen compounds is known from the pack cementation coating process and from high-temperature corrosion in certain industrial atmospheres. The approach was tested on different precursor alloys: Ti-43.5Al-4Nb-1Mo-0.1B (TNM-B1), TiNb42, and AlCu. Both dealloying effects and micro-scale pore formation were observed. The detailed size of the porous structures is in the range of 50 nm for both TNM-B1 and TiNB42 and 500 nm for AlCu. Full article
(This article belongs to the Section Porous Materials)
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19 pages, 765 KiB  
Article
Dynamics of a Magnetic Polaron in an Antiferromagnet
by Kaijun Shen, Maxim F. Gelin, Kewei Sun and Yang Zhao
Materials 2024, 17(2), 469; https://doi.org/10.3390/ma17020469 - 18 Jan 2024
Viewed by 858
Abstract
The t-J model remains an indispensable construct in high-temperature superconductivity research, bridging the gap between charge dynamics and spin interactions within antiferromagnetic matrices. This study employs the multiple Davydov Ansatz method with thermo-field dynamics to dissect the zero-temperature and finite-temperature behaviors. We uncover [...] Read more.
The t-J model remains an indispensable construct in high-temperature superconductivity research, bridging the gap between charge dynamics and spin interactions within antiferromagnetic matrices. This study employs the multiple Davydov Ansatz method with thermo-field dynamics to dissect the zero-temperature and finite-temperature behaviors. We uncover the nuanced dependence of hole and spin deviation dynamics on the spin–spin coupling parameter J, revealing a thermally-activated landscape where hole mobilities and spin deviations exhibit a distinct temperature-dependent relationship. This numerically accurate thermal perspective augments our understanding of charge and spin dynamics in an antiferromagnet. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Materials Physics)
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15 pages, 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 701
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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15 pages, 11105 KiB  
Article
Influence of Porosity on Fatigue Behaviour of 18Ni300 Steel SLM CT Specimens at Various Angles
by Pablo M. Cerezo, Jose A. Aguilera, Antonio Garcia-Gonzalez and Pablo Lopez-Crespo
Materials 2024, 17(2), 432; https://doi.org/10.3390/ma17020432 - 16 Jan 2024
Cited by 2 | Viewed by 836
Abstract
In order to improve understanding of the fatigue behaviour in additive manufactured samples, this research delves into the challenging interplay between building parameters, particularly fabrication angles, and the presence of pores. The primary objective is to explore the characterisation of these pores and [...] Read more.
In order to improve understanding of the fatigue behaviour in additive manufactured samples, this research delves into the challenging interplay between building parameters, particularly fabrication angles, and the presence of pores. The primary objective is to explore the characterisation of these pores and unravel their relationship with the fatigue properties of the material under investigation. Through a systematic analysis of porosity distribution in various fabrication orientations, supplemented by a detailed examination of the elemental dispersion around specific porous structures using energy-dispersive X-ray spectroscopy, a consistent behavioural pattern emerges across the samples. In assessing fatigue behaviour, an examination of the variables reveals that only area and aspect ratio significantly influence the behaviour of the samples. Such studies can contribute substantially to academic research in the field of material science and engineering. Full article
(This article belongs to the Special Issue Fatigue Crack Growth in Metallic Materials (Volume II))
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22 pages, 8943 KiB  
Article
Possibilities of Increasing the Durability of Dies Used in the Extrusion Process of Valve Forgings from Chrome-Nickel Steel by Using Alternative Materials from Hot-Work Tool Steels
by Marek Hawryluk, Marta Janik, Maciej Zwierzchowski, Marzena Małgorzata Lachowicz and Jakub Krawczyk
Materials 2024, 17(2), 346; https://doi.org/10.3390/ma17020346 - 10 Jan 2024
Cited by 1 | Viewed by 742
Abstract
This study refers to an analysis of the dies used in the first operation of producing a valve forging from chromium-nickel steel NC3015. The analyzed process of manufacturing forgings of exhaust valves is realized in the co-extrusion technology, followed by forging in closed [...] Read more.
This study refers to an analysis of the dies used in the first operation of producing a valve forging from chromium-nickel steel NC3015. The analyzed process of manufacturing forgings of exhaust valves is realized in the co-extrusion technology, followed by forging in closed dies. This type of technology is difficult to master, mainly due to the increased adhesion of the charge material to the tool substrate as well as the complex conditions of the tools’ operations, which are caused by the cyclic thermo-mechanical loads and also the hard tribological conditions. The average durability of tools made from tool steel WLV (1.2365), subjected to thermal treatment and nitriding, equals about 1000 forgings. In order to perform an in-depth analysis, a complex analysis of the presently realized technology was conducted in combination with multi-variant numerical simulations. The obtained results showed numerous cracks on the tools, especially in the cross-section reduction area, as well as sticking of the forging material, which, with insufficient control of the tribological conditions, can cause premature wear of the dies. In order to increase the durability of forging dies, alternative materials made of hot work tool steels were used: QRO90 Supreme, W360, and Unimax. The preliminary tests showed that the best results were obtained for QRO90, as the average durability for the tools made of this steel equaled about 1200 forgings (with an increase in both the minimal and maximal values), with reference to the 1000 forgings for the material applied so far. Full article
(This article belongs to the Special Issue Enhancing In-Use Properties of Advanced Steels)
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22 pages, 4577 KiB  
Review
Challenges for Field-Effect-Transistor-Based Graphene Biosensors
by Takao Ono, Satoshi Okuda, Shota Ushiba, Yasushi Kanai and Kazuhiko Matsumoto
Materials 2024, 17(2), 333; https://doi.org/10.3390/ma17020333 - 9 Jan 2024
Cited by 2 | Viewed by 2607
Abstract
Owing to its outstanding physical properties, graphene has attracted attention as a promising biosensor material. Field-effect-transistor (FET)-based biosensors are particularly promising because of their high sensitivity that is achieved through the high carrier mobility of graphene. However, graphene-FET biosensors have not yet reached [...] Read more.
Owing to its outstanding physical properties, graphene has attracted attention as a promising biosensor material. Field-effect-transistor (FET)-based biosensors are particularly promising because of their high sensitivity that is achieved through the high carrier mobility of graphene. However, graphene-FET biosensors have not yet reached widespread practical applications owing to several problems. In this review, the authors focus on graphene-FET biosensors and discuss their advantages, the challenges to their development, and the solutions to the challenges. The problem of Debye screening, in which the surface charges of the detection target are shielded and undetectable, can be solved by using small-molecule receptors and their deformations and by using enzyme reaction products. To address the complexity of sample components and the detection mechanisms of graphene-FET biosensors, the authors outline measures against nonspecific adsorption and the remaining problems related to the detection mechanism itself. The authors also introduce a solution with which the molecular species that can reach the sensor surfaces are limited. Finally, the authors present multifaceted approaches to the sensor surfaces that provide much information to corroborate the results of electrical measurements. The measures and solutions introduced bring us closer to the practical realization of stable biosensors utilizing the superior characteristics of graphene. Full article
(This article belongs to the Special Issue Research Progress on Two-Dimensional Materials)
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36 pages, 2816 KiB  
Review
Polymersomes as the Next Attractive Generation of Drug Delivery Systems: Definition, Synthesis and Applications
by Mariana Fonseca, Ivana Jarak, Francis Victor, Cátia Domingues, Francisco Veiga and Ana Figueiras
Materials 2024, 17(2), 319; https://doi.org/10.3390/ma17020319 - 8 Jan 2024
Cited by 3 | Viewed by 2448
Abstract
Polymersomes are artificial nanoparticles formed by the self-assembly process of amphiphilic block copolymers composed of hydrophobic and hydrophilic blocks. They can encapsulate hydrophilic molecules in the aqueous core and hydrophobic molecules within the membrane. The composition of block copolymers can be tuned, enabling [...] Read more.
Polymersomes are artificial nanoparticles formed by the self-assembly process of amphiphilic block copolymers composed of hydrophobic and hydrophilic blocks. They can encapsulate hydrophilic molecules in the aqueous core and hydrophobic molecules within the membrane. The composition of block copolymers can be tuned, enabling control of characteristics and properties of formed polymersomes and, thus, their application in areas such as drug delivery, diagnostics, or bioimaging. The preparation methods of polymersomes can also impact their characteristics and the preservation of the encapsulated drugs. Many methods have been described, including direct hydration, thin film hydration, electroporation, the pH-switch method, solvent shift method, single and double emulsion method, flash nanoprecipitation, and microfluidic synthesis. Considering polymersome structure and composition, there are several types of polymersomes including theranostic polymersomes, polymersomes decorated with targeting ligands for selective delivery, stimuli-responsive polymersomes, or porous polymersomes with multiple promising applications. Due to the shortcomings related to the stability, efficacy, and safety of some therapeutics in the human body, polymersomes as drug delivery systems have been good candidates to improve the quality of therapies against a wide range of diseases, including cancer. Chemotherapy and immunotherapy can be improved by using polymersomes to deliver the drugs, protecting and directing them to the exact site of action. Moreover, this approach is also promising for targeted delivery of biologics since they represent a class of drugs with poor stability and high susceptibility to in vivo clearance. However, the lack of a well-defined regulatory plan for polymersome formulations has hampered their follow-up to clinical trials and subsequent market entry. Full article
(This article belongs to the Special Issue Novel Nanosystems Composed of Amphiphilic Copolymers: Synthesis, Properties and Some Applications)
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20 pages, 3054 KiB  
Review
A Short Overview on Graphene and Graphene-Related Materials for Electrochemical Gas Sensing
by Mallikarjun Madagalam, Mattia Bartoli and Alberto Tagliaferro
Materials 2024, 17(2), 303; https://doi.org/10.3390/ma17020303 - 7 Jan 2024
Viewed by 1188
Abstract
The development of new and high-performing electrode materials for sensing applications is one of the most intriguing and challenging research fields. There are several ways to approach this matter, but the use of nanostructured surfaces is among the most promising and highest performing. [...] Read more.
The development of new and high-performing electrode materials for sensing applications is one of the most intriguing and challenging research fields. There are several ways to approach this matter, but the use of nanostructured surfaces is among the most promising and highest performing. Graphene and graphene-related materials have contributed to spreading nanoscience across several fields in which the combination of morphological and electronic properties exploit their outstanding electrochemical properties. In this review, we discuss the use of graphene and graphene-like materials to produce gas sensors, highlighting the most relevant and new advancements in the field, with a particular focus on the interaction between the gases and the materials. Full article
(This article belongs to the Special Issue Advanced Graphene and Graphene Oxide Materials)
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14 pages, 2515 KiB  
Article
Influence of Carbon-Based Fillers on the Electromagnetic Shielding Properties of a Silicone-Potting Compound
by Rafael Seidel, Konrad Katzer, Jakob Bieck, Maurice Langer, Julian Hesselbach and Michael Heilig
Materials 2024, 17(2), 280; https://doi.org/10.3390/ma17020280 - 5 Jan 2024
Viewed by 813
Abstract
The effect of carbon-based additives on adhesives and potting compounds with regard to electrical conductivity and electromagnetic interference (EMI) shielding properties is of great interest. The increasing power of wireless systems and the ever-higher frequency bands place new demands on shielding technology. This [...] Read more.
The effect of carbon-based additives on adhesives and potting compounds with regard to electrical conductivity and electromagnetic interference (EMI) shielding properties is of great interest. The increasing power of wireless systems and the ever-higher frequency bands place new demands on shielding technology. This publication gives an overview of the effect of carbon-based fillers on electrical conductivity, electromagnetic shielding properties, and the influence of different fillers and filler amounts on rheological behavior. This work focuses on carbon black (CB), recycled carbon fibers (rCF), carbon nanotubes (CNTs), and complex nanomaterials. Therefore, silicon samples with different fillers and filler amounts were prepared using a dual asymmetric centrifuge and a three-roll mill. It has been found that even with small filler amounts, the electromagnetic shielding properties were drastically raised. The filler content as well as the dispersion technique have a significant influence on most of the fillers. It has also been found that the complex viscosity is strongly influenced by the dispersion technique as well as by the choice and amount of filler. In the experiments carried out, shielding values of over 20 dB were achieved with several fillers, whereby even 43 dB were reached with complex, pre-crosslinked fillers. This signal reduction of up to 99.99% enables almost complete shielding of the related frequency. Full article
(This article belongs to the Section Carbon Materials)
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11 pages, 3428 KiB  
Article
Study on the Crystallization Behavior of Neodymium Rare-Earth Butadiene Rubber Blends and Its Effect on Dynamic Mechanical Properties
by Xiaohu Zhang, Wenbin Zhu, Xiaofan Li, Xinzheng Xie, Huan Ji, Yanxing Wei and Jifu Bi
Materials 2024, 17(1), 256; https://doi.org/10.3390/ma17010256 - 3 Jan 2024
Viewed by 826
Abstract
Utilizing neodymium-based butadiene rubber as a baseline, this study examines the effect of eco-friendly aromatic TDAE oil, fillers, and crosslinking reactions on neodymium-based rare-earth butadiene rubber (Nd-BR) crystallization behavior. The findings suggest that TDAE oil hinders crystallization, resulting in decreased crystallization temperatures and [...] Read more.
Utilizing neodymium-based butadiene rubber as a baseline, this study examines the effect of eco-friendly aromatic TDAE oil, fillers, and crosslinking reactions on neodymium-based rare-earth butadiene rubber (Nd-BR) crystallization behavior. The findings suggest that TDAE oil hinders crystallization, resulting in decreased crystallization temperatures and heightened activation energies (Ea). The crystallization activation energies for 20 parts per hundreds of rubber (PHR) and 37.5 PHR oil stand at −116.8 kJ/mol and −48.1 kJ/mol, respectively, surpassing the −264.3 kJ/mol of the unadulterated rubber. Fillers act as nucleating agents, hastening crystallization, which in turn elevates crystallization temperatures and diminishes Ea. In samples containing 20 PHR and 37.5 PHR oil, the incorporation of carbon black and silica brought the Ea down to −224.9 kJ/mol and −239.1 kJ/mol, respectively. Crosslinking considerably restricts molecular motion and crystallization potential. In the examined conditions, butadiene rubber containing 37.5 PHR oil displayed no crystallization following crosslinking, albeit crystallization was discernible with filler inclusion. Simultaneously, the crystallinity level sharply declined, manifesting cold crystallization behavior. The crosslinking process elevates Ea, while the equilibrium melting point (Tm0) noticeably diminishes. For instance, the Tm0 of pure Nd-BR is approximately −0.135 °C. When blended with carbon black and silica, the Tm0 values are −3.13 °C and −5.23 °C, respectively. After vulcanization, these values decrease to −21.6 °C and −10.16 °C. Evaluating the isothermal crystallization kinetics of diverse materials via the Avrami equation revealed that both the oil and crosslinking process can bring about a decrease in n values, with the Avrami index n for various samples oscillating between 1.5 and 2.5. Assessing the dynamic mechanical attributes of different specimens reveals that Nd-BR crystallization notably curtails its glass transition, marked by a modulus shift in the transition domain and a decrement in loss factor. The modulus in the rubbery state also witnesses a substantial augmentation. Full article
(This article belongs to the Section Polymeric Materials)
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13 pages, 2529 KiB  
Article
Design, Synthesis, and Spectral Properties of Novel 2-Mercaptobenzothiazole Derivatives
by Agnieszka Skotnicka and Janina Kabatc-Borcz
Materials 2024, 17(1), 246; https://doi.org/10.3390/ma17010246 - 2 Jan 2024
Cited by 1 | Viewed by 962
Abstract
This paper is focused on the optimalization of methods for the synthesis, isolation, and purification of 2-mercaptobenzothiazole-based acrylic and methacrylic monomers. The structures of the newly synthesized compounds were confirmed through infrared (IR) and nuclear magnetic resonance spectroscopy (NMR). Spectroscopic properties of the [...] Read more.
This paper is focused on the optimalization of methods for the synthesis, isolation, and purification of 2-mercaptobenzothiazole-based acrylic and methacrylic monomers. The structures of the newly synthesized compounds were confirmed through infrared (IR) and nuclear magnetic resonance spectroscopy (NMR). Spectroscopic properties of the resulting 2-mercaptobenzothiazole derivatives were determined based on their absorption spectra and molar absorption coefficients in solvents with varying polarities. A correlation was established between the calculated density functional theory (DFT) energies and Frontier Molecular Orbitals and the experimental observations, confirming their consistency. The practical utility of the synthesized compounds, particularly in future polymerization processes, hinges on a thorough understanding of these properties. Full article
(This article belongs to the Special Issue Feature Paper in the Section 'Polymeric Materials' (2nd Edition))
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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 2109
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
(This article belongs to the Special Issue Surface Modifications and Coatings: Processing, Characterization, and Applications)
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14 pages, 6311 KiB  
Article
Rapid Growth of Metal–Metal Oxide Core–Shell Structures through Joule Resistive Heating: Morphological, Structural, and Luminescence Characterization
by Juan Francisco Ramos-Justicia, Ana Urbieta and Paloma Fernández
Materials 2024, 17(1), 208; https://doi.org/10.3390/ma17010208 - 30 Dec 2023
Cited by 1 | Viewed by 907
Abstract
The aim of this study is to prove that resistive heating enables the synthesis of metal/metal oxide composites in the form of core–shell structures. The thickness and morphology of the oxide layer depends strongly on the nature of the metal, but the influences [...] Read more.
The aim of this study is to prove that resistive heating enables the synthesis of metal/metal oxide composites in the form of core–shell structures. The thickness and morphology of the oxide layer depends strongly on the nature of the metal, but the influences of parameters such as the time and current profiles and the presence of an external field have also been investigated. The systems chosen for the present study are Zn/ZnO, Ti/TiO2, and Ni/NiO. The characterization of the samples was performed using techniques based on scanning electron microscopy (SEM). The thicknesses of the oxide layers varied from 10 μm (Zn/ZnO) to 50 μm (Ni/NiO). In the case of Zn- and Ti-based composites, the growth of nanostructures on the oxide layer was observed. Micro- and nanoneedles formed on the ZnO layer while prism-like structures appeared on the TiO2. In the case of the NiO layer, micro- and nanocrystals were observed. Applying an external electric field seemed to align the ZnO needles, whereas its effect on TiO2 and NiO was less appreciable, principally affecting the shape of their grain boundaries. The chemical compositions were analysed using X-ray spectroscopy (EDX), which confirmed the existence of an oxide layer. Structural information was obtained by means of X-ray diffraction (XRD) and was later checked using Raman spectroscopy. The oxide layers seemed to be crystalline and, although some non-stoichiometric phases appeared, the stoichiometric phases were predominant; these were wurtzite, rutile, and cubic for Zn, Ti, and Ni oxides, respectively. The photoluminescence technique was used to study the distribution of defects on the shell, and mainly visible bands (2–2.5 eV), attributed to oxygen vacancies, were present. The near-band edges of ZnO and TiO2 were also observed around 3.2–3.3 eV. Full article
(This article belongs to the Special Issue Advantages and Perspectives of ZnO Nanostructured Materials)
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20 pages, 15729 KiB  
Article
Atomistic-Continuum Study of an Ultrafast Melting Process Controlled by a Femtosecond Laser-Pulse Train
by Yu Meng, An Gong, Zhicheng Chen, Qingsong Wang, Jianwu Guo, Zihao Li and Jiafang Li
Materials 2024, 17(1), 185; https://doi.org/10.3390/ma17010185 - 29 Dec 2023
Cited by 1 | Viewed by 930
Abstract
In femtosecond laser fabrication, the laser-pulse train shows great promise in improving processing efficiency, quality, and precision. This research investigates the influence of pulse number, pulse interval, and pulse energy ratio on the lateral and longitudinal ultrafast melting process using an experiment and [...] Read more.
In femtosecond laser fabrication, the laser-pulse train shows great promise in improving processing efficiency, quality, and precision. This research investigates the influence of pulse number, pulse interval, and pulse energy ratio on the lateral and longitudinal ultrafast melting process using an experiment and the molecular dynamics coupling two-temperature model (MD-TTM model), which incorporates temperature-dependent thermophysical parameters. The comparison of experimental and simulation results under single and double pulses proves the reliability of the MD-TTM model and indicates that as the pulse number increases, the melting threshold at the edge region of the laser spot decreases, resulting in a larger diameter of the melting region in the 2D lateral melting results. Using the same model, the lateral melting results of five pulses are simulated. Moreover, the longitudinal melting results are also predicted, and an increasing pulse number leads to a greater early-stage melting depth in the melting process. In the case of double femtosecond laser pulses, the pulse interval and pulse energy ratio also affect the early-stage melting depth, with the best enhancement observed with a 2 ps interval and a 3:7 energy ratio. However, pulse number, pulse energy ratio, and pulse interval do not affect the final melting depth with the same total energies. The findings mean that the phenomena of melting region can be flexibly manipulated through the laser-pulse train, which is expected to be applied to improve the structural precision and boundary quality. Full article
(This article belongs to the Section Materials Physics)
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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 2 | Viewed by 968
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
Cited by 2 | Viewed by 962
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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14 pages, 6019 KiB  
Article
Multiscale Analysis of Composite Structures with Artificial Neural Network Support for Micromodel Stress Determination
by Wacław Kuś, Waldemar Mucha and Iyasu Tafese Jiregna
Materials 2024, 17(1), 154; https://doi.org/10.3390/ma17010154 - 27 Dec 2023
Viewed by 891
Abstract
Structures made of heterogeneous materials, such as composites, often require a multiscale approach when their behavior is simulated using the finite element method. By solving the boundary value problem of the macroscale model, for previously homogenized material properties, the resulting stress maps can [...] Read more.
Structures made of heterogeneous materials, such as composites, often require a multiscale approach when their behavior is simulated using the finite element method. By solving the boundary value problem of the macroscale model, for previously homogenized material properties, the resulting stress maps can be obtained. However, such stress results do not describe the actual behavior of the material and are often significantly different from the actual stresses in the heterogeneous microstructure. Finding high-accuracy stress results for such materials leads to time-consuming analyses in both scales. This paper focuses on the application of machine learning to multiscale analysis of structures made of composite materials, to substantially decrease the time of computations of such localization problems. The presented methodology was validated by a numerical example where a structure made of resin epoxy with randomly distributed short glass fibers was analyzed using a computational multiscale approach. Carefully prepared training data allowed artificial neural networks to learn relationships between two scales and significantly increased the efficiency of the multiscale approach. Full article
(This article belongs to the Special Issue Computational Modelling and Design of Novel Engineering Materials (Second Edition))
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35 pages, 6148 KiB  
Review
Titanium Alloy Implants with Lattice Structures for Mandibular Reconstruction
by Khaled M. Hijazi, S. Jeffrey Dixon, Jerrold E. Armstrong and Amin S. Rizkalla
Materials 2024, 17(1), 140; https://doi.org/10.3390/ma17010140 - 27 Dec 2023
Cited by 1 | Viewed by 1333
Abstract
In recent years, the field of mandibular reconstruction has made great strides in terms of hardware innovations and their clinical applications. There has been considerable interest in using computer-aided design, finite element modelling, and additive manufacturing techniques to build patient-specific surgical implants. Moreover, [...] Read more.
In recent years, the field of mandibular reconstruction has made great strides in terms of hardware innovations and their clinical applications. There has been considerable interest in using computer-aided design, finite element modelling, and additive manufacturing techniques to build patient-specific surgical implants. Moreover, lattice implants can mimic mandibular bone’s mechanical and structural properties. This article reviews current approaches for mandibular reconstruction, their applications, and their drawbacks. Then, we discuss the potential of mandibular devices with lattice structures, their development and applications, and the challenges for their use in clinical settings. Full article
(This article belongs to the Section Biomaterials)
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17 pages, 3801 KiB  
Article
A Machine Learning Approach for Modelling Cold-Rolling Curves for Various Stainless Steels
by Julia Contreras-Fortes, M. Inmaculada Rodríguez-García, David L. Sales, Rocío Sánchez-Miranda, Juan F. Almagro and Ignacio Turias
Materials 2024, 17(1), 147; https://doi.org/10.3390/ma17010147 - 27 Dec 2023
Viewed by 1002
Abstract
Stainless steel is a cold-work-hardened material. The degree and mechanism of hardening depend on the grade and family of the steel. This characteristic has a direct effect on the mechanical behaviour of stainless steel when it is cold-formed. Since cold rolling is one [...] Read more.
Stainless steel is a cold-work-hardened material. The degree and mechanism of hardening depend on the grade and family of the steel. This characteristic has a direct effect on the mechanical behaviour of stainless steel when it is cold-formed. Since cold rolling is one of the most widespread processes for manufacturing flat stainless steel products, the prediction of their strain-hardening mechanical properties is of great importance to materials engineering. This work uses artificial neural networks (ANNs) to forecast the mechanical properties of the stainless steel as a function of the chemical composition and the applied cold thickness reduction. Multiple linear regression (MLR) is also used as a benchmark model. To achieve this, both traditional and new-generation austenitic, ferritic, and duplex stainless steel sheets are cold-rolled at a laboratory scale with different thickness reductions after the industrial intermediate annealing stage. Subsequently, the mechanical properties of the cold-rolled sheets are determined by tensile tests, and the experimental cold-rolling curves are drawn based on those results. A database is created from these curves to generate a model applying machine learning techniques to predict the values of the tensile strength (Rm), yield strength (Rp), hardness (H), and elongation (A) based on the chemical composition and the applied cold thickness reduction. These models can be used as supporting tools for designing and developing new stainless steel grades and/or adjusting cold-forming processes. Full article
(This article belongs to the Special Issue Machine Learning Techniques in Materials Science and Engineering)
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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
Cited by 1 | Viewed by 1405
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
(This article belongs to the Special Issue Towards a Sustainable and Recyclable Future with Wood and Wood-Based Composites)
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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
Cited by 1 | Viewed by 1082
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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