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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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39 pages, 1816 KB  
Review
Progress in Additive Manufacturing of High-Entropy Alloys
by Bin Chen
Materials 2024, 17(23), 5917; https://doi.org/10.3390/ma17235917 - 3 Dec 2024
Cited by 10 | Viewed by 5354
Abstract
High-entropy alloys (HEAs) have drawn substantial attention on account of their outstanding properties. Additive manufacturing (AM), which has emerged as a successful approach for fabricating metallic materials, allows for the production of complex components based on three-dimensional (3D) computer-aided design (CAD) models. This [...] Read more.
High-entropy alloys (HEAs) have drawn substantial attention on account of their outstanding properties. Additive manufacturing (AM), which has emerged as a successful approach for fabricating metallic materials, allows for the production of complex components based on three-dimensional (3D) computer-aided design (CAD) models. This paper reviews the advancements in the AM of HEAs, encompassing a variety of AM techniques, including selective laser melting (SLM), selective laser sintering (SLS), selective electron beam melting (SEBM), directed energy deposition (DED), binder jetting (BJT), direct ink writing (DIW), and additive friction stir deposition (AFSD). Additionally, the study discusses the powders and wires utilized in AM, the post-processing of AM-processed HEAs, as well as the mechanical and corrosion properties of these alloys. The unique ultra-fine and non-equilibrium microstructures achieved through AM result in superior mechanical properties of HEAs, like improved strength and ductility. However, research regarding certain aspects of HEA AM, such as fatigue properties and creep deformation behavior, is still relatively scarce. Future research should focus on overcoming the existing limitations and exploring the potential of HEAs in various applications. Full article
(This article belongs to the Special Issue Advances in Multicomponent Alloy Design, Simulation and Properties)
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14 pages, 5593 KB  
Article
Influence of Selected Factors of Vibratory Work Hardening Machining on the Properties of CuZn30 Brass
by Damian Bańkowski, Anna Kiljan, Irena M. Hlaváčová and Piotr Młynarczyk
Materials 2024, 17(23), 5913; https://doi.org/10.3390/ma17235913 - 3 Dec 2024
Cited by 2 | Viewed by 1008
Abstract
The purpose of this study was to determine the effect of selected vibratory strengthening machining factors on the properties of CuZn30 brass. Vibratory strengthening machining was carried out using metal media dedicated to polishing processes, which also contributed to strengthening the treated surfaces. [...] Read more.
The purpose of this study was to determine the effect of selected vibratory strengthening machining factors on the properties of CuZn30 brass. Vibratory strengthening machining was carried out using metal media dedicated to polishing processes, which also contributed to strengthening the treated surfaces. The test samples were cut with an abrasive water jet and recrystallized to obtain a soft microstructure. An orthogonal, two-factor five-level plan was used for the study. The effect of vibration frequency and vibratory machining time on selected changes in parameters of the geometric structure of the surface and hardness of the surface layer was determined using Statistica software version 10 (64-bit). Higher vibration frequencies for vibratory machining increased the hardness of machined surfaces by as much as 50 HV0.02. The arithmetic mean deviation of the height of surface irregularities from the reference plane, Sa, decreases with increasing the time of vibratory machining. A value of Sa = 0.168 µm was obtained after 87 min of consolidation, compared to an initial surface of Sa = 0.65 µm. Full article
(This article belongs to the Special Issue Material Surface Topography Measurement, Analysis and Characterization)
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14 pages, 9110 KB  
Article
Surface-Grinding-Induced Recrystallization and Metal Flow Causes Corrosion-Assisted Penetrating Attack of High-Mn–Low-CR Casting Steel in Humid Environments
by Jin Sung Park, Myeong Hun Kang and Sung Jin Kim
Materials 2024, 17(23), 5922; https://doi.org/10.3390/ma17235922 - 3 Dec 2024
Cited by 3 | Viewed by 1122
Abstract
This study examined the surface-grinding-induced microstructural modifications and corrosion attacks in a penetrating form of a high-Mn–low-Cr casting steel slab under humid environments. Various experimental and analytical findings from field-emission scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and electrochemical analyses revealed [...] Read more.
This study examined the surface-grinding-induced microstructural modifications and corrosion attacks in a penetrating form of a high-Mn–low-Cr casting steel slab under humid environments. Various experimental and analytical findings from field-emission scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and electrochemical analyses revealed that the abrasive grinding process led to the formation of a surface deformed region, comprising a recrystallized fine grain layer and multiple streamlines. Corrosion initially occurs preferentially along the boundary areas where Cr(Mn)23C6 particles are precipitated. Moreover, the corrosion products (Fe-based oxy/hydroxides) with a high volumetric expansion ratio detach readily from the surface deformed regions, facilitating the easy penetration of corrosive media. In contrast to conventional low-alloyed steels, which exhibit uniform corrosion behavior, corrosion-assisted penetrating attacks on ground high-Mn–low-Cr casting steel slabs occur more severely and frequently during the summer/dry season (i.e., relative humidity levels around 60% to 80%, rather than 100%) when a thin water film can form on the steel surface. Based on the result, effective technical strategies in terms of metallurgical and environmental aspects to mitigate the risk of corrosion-assisted penetrating attack of high-Mn–low-Cr casting steel were discussed. Full article
(This article belongs to the Special Issue Recent Progress in Corrosion Protection and Electrochemical Characterization of New and Advanced Materials)
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22 pages, 6271 KB  
Article
Evaluating the Impact of Sample Irregularities on the Dynamic Stiffness of Polyurethane: Insights from Experimental and FEM Analysis
by Krzysztof Nering, Arkadiusz Kwiecień and Konrad Nering
Materials 2024, 17(23), 5910; https://doi.org/10.3390/ma17235910 - 3 Dec 2024
Cited by 2 | Viewed by 1103
Abstract
This study investigates the dynamic stiffness and damping characteristics of three polyurethane materials—PM, PS, and PST—using a comprehensive vibroacoustic testing approach. The aim is to examine material parameters such as dynamic stiffness, Young’s modulus, critical damping factor, and the influence of sample irregularities [...] Read more.
This study investigates the dynamic stiffness and damping characteristics of three polyurethane materials—PM, PS, and PST—using a comprehensive vibroacoustic testing approach. The aim is to examine material parameters such as dynamic stiffness, Young’s modulus, critical damping factor, and the influence of sample irregularities on the accuracy of measurements. The study employs both experimental testing, in which cuboidal and cylindrical polyurethane samples were subjected to sinusoidal excitation, and finite element modeling (FEM) to simulate the test conditions in sample without irregularities. Results indicate that sample contact surface irregularities (even as low as ~0.04 mm) significantly impact the measured dynamic stiffness, with the effect intensifying for materials with higher Young’s modulus values (above 5 MPa). Furthermore, cylindrical samples demonstrated more stable and repeatable measurements compared to cuboidal samples, where surface irregularities were tested in a more controlled environment. The findings underscore the need to consider sample geometry and irregularities in dynamic stiffness assessments to ensure better material evaluations. This work contributes valuable insights for the accurate modeling and testing of materials used in vibration isolation and sound insulation contexts. Full article
(This article belongs to the Special Issue Research on Properties of Polymers and Their Engineering Applications)
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9 pages, 2917 KB  
Communication
Microstructure Optimization of Thermoelectric τ1-Al2Fe3Si3 via Graded Temperature Heat Treatments
by Ryuta Yurishima, Yoshiki Takagiwa, Ayako Ikeda and Teruyuki Ikeda
Materials 2024, 17(23), 5899; https://doi.org/10.3390/ma17235899 - 2 Dec 2024
Cited by 1 | Viewed by 1099
Abstract
To investigate the relationship between microstructure, chemical composition, and thermoelectric properties, we have applied graded temperature heat treatments to recently developed τ1-Al2Fe3Si3-based thermoelectric (FAST) materials formed by a peritectic reaction. We investigated microstructures, chemical compositions, [...] Read more.
To investigate the relationship between microstructure, chemical composition, and thermoelectric properties, we have applied graded temperature heat treatments to recently developed τ1-Al2Fe3Si3-based thermoelectric (FAST) materials formed by a peritectic reaction. We investigated microstructures, chemical compositions, and Seebeck coefficients as continuous functions of heat treatment temperature. The τ1 phase can become p- and n-type semiconductors without doping by changing the Al/Si ratio. The Seebeck coefficient was maximized, exceeding |S| > 140 μVK−1 for both p- and n-type materials, by heat treatment at 1173 K for 24 h through microstructural optimization. These results show that combining the graded temperature heat treatments and spatial mapping measurements of thermoelectric properties gives effective routes to determine the suitable heat treatment temperature for materials with multiphase microstructure. Full article
(This article belongs to the Special Issue Structure and Properties of Advanced Thermoelectric Materials and Devices)
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18 pages, 3164 KB  
Article
Bioactive Compounds from Banana Leaf Extracts: Influence of Extraction Methodologies and Their Integration into Knitted Hemp Fabrics
by Joana Mota Gomes, João Mariz, Catarina Rodrigues, Ana Luísa Alves, Joana Moreira, Bárbara Vieira, Rosa Maria Silva, Andrea Zille and Carla Joana Silva
Materials 2024, 17(23), 5884; https://doi.org/10.3390/ma17235884 - 30 Nov 2024
Cited by 2 | Viewed by 3282
Abstract
This study explores the bioactive potential of banana leaf extracts and their innovative integration into knitted hemp fabrics. To obtain the extracts, distinct extraction methodologies were employed, namely conventional extraction, ultrasound-assisted extraction, and pressurized-liquid extraction. Aqueous and hydroethanolic solvents, namely 20% (v [...] Read more.
This study explores the bioactive potential of banana leaf extracts and their innovative integration into knitted hemp fabrics. To obtain the extracts, distinct extraction methodologies were employed, namely conventional extraction, ultrasound-assisted extraction, and pressurized-liquid extraction. Aqueous and hydroethanolic solvents, namely 20% (v/v) and 50% (v/v), were employed during the extraction process. Furthermore, the cationization and functionalization of knitted hemp fabrics with the banana leaf extracts was achieved through padding. The extracts’ phenolic content and antioxidant activity were evaluated using the Folin–Ciocalteu (FC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, respectively. The results indicated that both ultrasound-assisted extraction and pressurized-assisted extraction substantially enhanced the yield of phenolic compounds in comparison to conventional extraction, while employing 50% EtOH as a solvent also improved extraction yields for all extraction methodologies. The functionalized knits were further characterized concerning their antioxidant activity by DPPH, assessing their antimicrobial properties through ATCC TM-100 standard against three microorganisms (Staphylococcus aureus, Candida Krusei, and Candida albicans), and UV protection according to the standard AS/NZS 4399:2017. Antioxidant activity was highest in knits functionalized with extracts obtained via ultrasound-assisted extraction, while antimicrobial properties were most pronounced in knits treated with hydroalcoholic extracts, particularly those derived from assisted methods. The UV protection was enhanced in extracts with higher ethanol concentrations obtained through ultrasound-assisted extraction, with these knits exhibiting the highest Ultraviolet Protection Factor (UPF). This research not only highlights the efficacy of the alternative extraction technologies but also offers valuable insights for the development of innovative, biocompatible materials with enhanced bioactive properties for diverse applications in the textile and healthcare sectors, paving the way for sustainable applications. Full article
(This article belongs to the Special Issue Leather, Textiles and Bio-Based Materials)
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16 pages, 1313 KB  
Article
The Shrinking Fermi Liquid Scenario for Cuprates Under the Scrutiny of Optical Conductivity Measurements
by Sergio Caprara, Carlo Di Castro, Giovanni Mirarchi, Götz Seibold and Marco Grilli
Materials 2024, 17(23), 5849; https://doi.org/10.3390/ma17235849 - 28 Nov 2024
Viewed by 806
Abstract
In a recent paper [B. Michon et al., Nat. Commun. (2023) 14:3033], optical conductivity experiments in cuprate superconductors were shown to display scaling properties consistent with the Marginal Fermi Liquid theory. Here, we argue that the temperature regime studied in these experiments does [...] Read more.
In a recent paper [B. Michon et al., Nat. Commun. (2023) 14:3033], optical conductivity experiments in cuprate superconductors were shown to display scaling properties consistent with the Marginal Fermi Liquid theory. Here, we argue that the temperature regime studied in these experiments does not allow for distinguishing between Marginal Fermi Liquid and Shrinking Fermi Liquid. In the latter scenario, which we recently proposed and which applies near a quantum critical point, dynamical fluctuations of the order parameter with a short correlation length mediate a nearly isotropic scattering among the quasiparticles over the entire Fermi surface leading to strange metal behavior. If the damping of these nearly local fluctuations increases by decreasing the temperature, the Fermi liquid regime shrinks and the strange metal behavior is extended to the lowest temperatures. This Shrinking Fermi Liquid scenario has many similarities and some differences with respect to the Marginal Fermi Liquid theory. In particular, we show that the approximate scaling properties of the optical conductivity in some high-frequency regimes predicted by the Shrinking Fermi Liquid scenario account for a very good description of the experimental data. Full article
(This article belongs to the Special Issue Advances in Cuprates and Iron-Based Superconductors: Physics, Properties, and Applications)
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25 pages, 1721 KB  
Review
Hydrogels and Their Functionalization—Analysis of the Possibility of Their Application in Post-Fire Water Treatment Processes
by Anna Rabajczyk, Justyna Gniazdowska, Piotr Stojek, Katarzyna Czyżewska, Anna Trusek and Karolina Labus
Materials 2024, 17(23), 5820; https://doi.org/10.3390/ma17235820 - 27 Nov 2024
Cited by 5 | Viewed by 2658
Abstract
Increasingly intense changes in climatic conditions and the use of modified materials are causing fires, the consequences of which are increasingly serious for the environment. On one hand, there is the issue of access to water resources. On the other hand, there is [...] Read more.
Increasingly intense changes in climatic conditions and the use of modified materials are causing fires, the consequences of which are increasingly serious for the environment. On one hand, there is the issue of access to water resources. On the other hand, there is the problem of post-fire wastewater, which often contains a mixture of simple inorganic compounds and complex organic molecules, making the removal of pollutants a difficult task requiring innovative approaches. Among these solutions, hydrogels stand out as a promising class of sorption materials. Depending on their synthesis or functionalization, hydrogels can effectively capture contaminants and facilitate the reduction or removal of specific pollutants. This study explores the functionalization of polymeric materials, specifically hydrogels, using microorganisms or bioactive substances to create materials capable of treating water contaminated with hazardous substances generated during firefighting incidents. The possibility of wastewater capture was also taken into account to retain pretreated water at the place of pollutant generation. The analysis covered the potential, conditions, and limitations of using hydrogels in post-fire operations for the effective management of contaminated waters. It was shown that hydrogels, depending on the modification, have the potential to capture wastewater and purify it from both organic and inorganic substances specific to post-fire wastewater. However, it is not possible for a given hydrogel to meet all desired expectations at the same time. Furthermore, modifications that facilitate the optimal performance of certain functionalities may render the others ineffective. Full article
(This article belongs to the Special Issue Functional Hydrogels: Design, Properties and Applications)
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37 pages, 15018 KB  
Review
Graphene-Based Fiber Materials for Gas Sensing Applications: State of the Art Review
by Susanna Vu, Mohamed Siaj and Ricardo Izquierdo
Materials 2024, 17(23), 5825; https://doi.org/10.3390/ma17235825 - 27 Nov 2024
Viewed by 2056
Abstract
The importance of gas sensors is apparent as the detection of gases and pollutants is crucial for environmental monitoring and human safety. Gas sensing devices also hold the potential for medical applications as health monitoring and disease diagnostic tools. Gas sensors fabricated from [...] Read more.
The importance of gas sensors is apparent as the detection of gases and pollutants is crucial for environmental monitoring and human safety. Gas sensing devices also hold the potential for medical applications as health monitoring and disease diagnostic tools. Gas sensors fabricated from graphene-based fibers present a promising advancement in the field of sensing technology due to their enhanced sensitivity and selectivity. The diverse chemical and mechanical properties of graphene-based fibers—such as high surface area, flexibility, and structural stability—establish them as ideal gas-sensing materials. Most significantly, graphene fibers can be readily tuned to detect a wide range of gases, making them highly versatile in gas-sensing technologies. This review focuses on graphene-based composite fibers for gas sensors, with an emphasis on the preparation processes used to achieve these fibers and the gas sensing mechanisms involved in their sensors. Graphene fiber gas sensors are presented based on the chemical composition of their target gases, with detailed discussions on their sensitivity and performance. This review reveals that graphene-based fibers can be prepared through various methods and can be effectively integrated into gas-sensing devices for a diverse range of applications. By presenting an overview of developments in this field over the past decade, this review highlights the potential of graphene-based fiber sensors and their prospective integration into future technologies. Full article
(This article belongs to the Special Issue Advanced Nanocomposites Materials Based on Graphene Oxide/Reduced Graphene Oxide: Potential Applications and Perspectives)
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14 pages, 5465 KB  
Article
Thin and Flexible PANI/PMMA/CNF Forest Films Produced via a Two-Step Floating Catalyst Chemical Vapor Deposition
by Foteini-Maria Papadopoulou, Spyros Soulis, Aikaterini-Flora A. Trompeta and Costas A. Charitidis
Materials 2024, 17(23), 5812; https://doi.org/10.3390/ma17235812 - 27 Nov 2024
Viewed by 1356
Abstract
In this paper, we explore a straightforward two-step method to produce high-purity, vertically aligned multi-walled carbon nanofibres (MWCNFs) via chemical vapor deposition (CVD). Two distinct solutions are utilized for this CVD method: a catalytic solution consisting of ferrocene and acetonitrile (ACN) and a [...] Read more.
In this paper, we explore a straightforward two-step method to produce high-purity, vertically aligned multi-walled carbon nanofibres (MWCNFs) via chemical vapor deposition (CVD). Two distinct solutions are utilized for this CVD method: a catalytic solution consisting of ferrocene and acetonitrile (ACN) and a carbon source solution with camphor and ACN. The vapors of the catalytic solution inserted in the reaction chamber through external boiling result in a floating catalyst CVD approach that produces vertically aligned CNFs in a consistent manner. CNFs are grown in a conventional CVD horizontal reactor at 850 °C under atmospheric pressure and characterized by Raman spectroscopy, scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Coating the MWCNTs with polymethyl methacrylate (PMMA) while still on the Si substrate retains the structure and results in a flexible, conductive thin film suitable for flexible electrodes. The film is 62 μm thick and stable in aqueous solutions, capable of withstanding further processing, such as electropolymerization with polyaniline, to be used for energy storage applications. Full article
(This article belongs to the Special Issue Emerging Technologies for Development of Novel Materials Systems and Coatings (Volume 2))
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14 pages, 2827 KB  
Article
The Coloring Mechanism of Opaque Glazes from the Changsha Kiln of the Tang Dynasty
by Lala Jia, Maolin Zhang, Yongqiang Yu, Zihan Li and Yongbin Yu
Materials 2024, 17(23), 5803; https://doi.org/10.3390/ma17235803 - 27 Nov 2024
Cited by 1 | Viewed by 1273
Abstract
The Changsha Kiln of the Tang Dynasty was a major site for celadon production, yet the mechanisms behind the unique coloring of its opaque glazes remain inadequately explored. Prior research has largely focused on the general composition of these glazes, with limited understanding [...] Read more.
The Changsha Kiln of the Tang Dynasty was a major site for celadon production, yet the mechanisms behind the unique coloring of its opaque glazes remain inadequately explored. Prior research has largely focused on the general composition of these glazes, with limited understanding of the specific processes contributing to their distinct visual characteristics. This gap in knowledge hinders efforts to accurately replicate these historical glazes and fully appreciate their technological significance. In this study, we analyze the chemical composition and microstructure of opaque glaze specimens from the Changsha Kiln using advanced techniques such as EDXRF, SEM-EDS, and ultra-deep field microscopy. Our findings reveal that the opaque glazes are high-calcium compositions where phase separation and the presence of coloring ions like Cu2+, Cu+, and Fe3+ play critical roles in determining the glaze’s color. The interplay between chemical coloring and phase separation processes is shown to produce the distinct blue-green and creamy white hues observed in the glazes. These results provide a deeper understanding of the coloring mechanisms in Changsha Kiln glazes, contributing to the broader field of ceramic research and aiding in the preservation and accurate reproduction of these historic artifacts. Full article
(This article belongs to the Special Issue Advanced Characterization Approaches Applied to the Field of Cultural Heritage: From Conservation to Divulgation)
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14 pages, 11006 KB  
Article
The Influence of the Steam Sterilization Process on Selected Properties of Polymer Samples Produced in MEX and JMT Processes
by Małgorzata Zaborniak, Janusz Kluczyński, Jakub Stańko and Tomasz Ślęzak
Materials 2024, 17(23), 5763; https://doi.org/10.3390/ma17235763 - 25 Nov 2024
Cited by 1 | Viewed by 1675
Abstract
Polymeric materials are widely used in medical engineering, and with the dynamic development of additive manufacturing (AM) technology, increasing attention is being paid to research on the mechanical strength of composite polymer structures. At the same time, the impact of sterilization on, for [...] Read more.
Polymeric materials are widely used in medical engineering, and with the dynamic development of additive manufacturing (AM) technology, increasing attention is being paid to research on the mechanical strength of composite polymer structures. At the same time, the impact of sterilization on, for example, surgical templates and the influence of the sterilization process on the geometry of these parts have not been sufficiently studied. In this work, the effect of steam sterilization on samples made of polymer materials for medical applications was presented. This research was carried out on samples with normative geometry made of polyetheretherketone (PEEK) polymers produced using the Material Extrusion (MEX) AM process and acrylic formulation (MED610) produced by Jetting Modeling Technology (JMT). These materials provide biocompatibility, which makes them suitable for potential medical applications. Steam sterilization was performed in an autoclave at temperatures of 121 °C and 134 °C. The three-point bending strength properties were determined according to ISO 178 standards. An INSTRON 5967 strength testing machine was used for those tests. Surface roughness analysis (according to ISO 21920) was performed and presented in 2D and 3D surface views using the Mountains Map Software (version 6.0). Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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21 pages, 23836 KB  
Article
Electron Beam Welding of Dissimilar Stainless Steel and Maraging Steel Joints
by Matúš Geľatko, Radoslav Vandžura, František Botko and Michal Hatala
Materials 2024, 17(23), 5769; https://doi.org/10.3390/ma17235769 - 25 Nov 2024
Cited by 4 | Viewed by 1400
Abstract
The incorporation of additive manufactured (AM) metal parts to real assemblies is a crucial issue for the increasing of their industrial utilization. The presented research is devoted to the electron beam welding (EBW) of dissimilar steel joints. Dissimilarity is defined by the various [...] Read more.
The incorporation of additive manufactured (AM) metal parts to real assemblies is a crucial issue for the increasing of their industrial utilization. The presented research is devoted to the electron beam welding (EBW) of dissimilar steel joints. Dissimilarity is defined by the various types of steel and manufacturing processes used for the creation of specimens. Conventional AISI 316 stainless steel, selective laser melted (SLM) SS 316L stainless steel, and SLM M300 maraging steel were welded at variable parameters in the form of a welding current and a welding velocity. EBW joints were evaluated considering the macroscopic and microscopic characteristics, as well as a reached microhardness. The obtained preliminary results represent important input data for the follow-up experiments focused on the setting of optimal EBW parameters of welding the dissimilar joints including SLM products, with the consideration of their basic macroscopical and microscopical characteristics, mechanical properties, and residual stresses. Full article
(This article belongs to the Special Issue Advanced Production, Processing and Characterization of Industrial Materials)
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18 pages, 4444 KB  
Article
Toward Sustainable 3D-Printed Sensor: Green Fabrication of CNT-Enhanced PLA Nanocomposite via Solution Casting
by Javid Sharifi, Ghaus Rizvi and Haniyeh (Ramona) Fayazfar
Materials 2024, 17(23), 5782; https://doi.org/10.3390/ma17235782 - 25 Nov 2024
Cited by 4 | Viewed by 1522
Abstract
The current study explores, for the first time, an eco-friendly solution casting method using a green solvent, ethyl acetate, to prepare feedstock/filaments from polylactic acid (PLA) biopolymer reinforced with carbon nanotubes (CNTs), followed by 3D printing and surface activation for biosensing applications. Comprehensive [...] Read more.
The current study explores, for the first time, an eco-friendly solution casting method using a green solvent, ethyl acetate, to prepare feedstock/filaments from polylactic acid (PLA) biopolymer reinforced with carbon nanotubes (CNTs), followed by 3D printing and surface activation for biosensing applications. Comprehensive measurements of thermal, electrical, rheological, microstructural, and mechanical properties of developed feedstock and 3D-printed parts were performed and analyzed. Herein, adding 2 wt.% CNTs to the PLA matrix marked the electrical percolation, achieving conductivity of 8.3 × 10−3 S.m−1, thanks to the uniform distribution of CNTs within the PLA matrix facilitated by the solution casting method. Rheological assessments paralleled these findings; the addition of 2 wt.% CNTs transitioned the nanocomposite from liquid-like to a solid-like behavior with a percolated network structure, significantly elevating rheological properties compared to the composite with 1 wt.% CNTs. Mechanical evaluations of the printed samples revealed improvement in tensile strength and modulus compared to virgin PLA by a uniform distribution of 2 wt.% CNTs into PLA, with an increase of 14.5% and 10.3%, respectively. To further enhance the electrical conductivity and sensing capabilities of the developed samples, an electrochemical surface activation treatment was applied to as-printed nanocomposite samples. The field-emission scanning electron microscopy (FE-SEM) analysis confirmed that this surface activation effectively exposed the CNTs to the surface of 3D-printed parts by removing a thin layer of polymer from the surface, thereby optimizing the composite’s electroconductivity performance. The findings of this study underscore the potential of the proposed eco-friendly method in developing advanced 3D-printed bio-nanocomposites based on carbon nanotubes and biopolymers, using a green solution casting and cost-effective material extrusion 3D-printing method, for electrochemical-sensing applications. Full article
(This article belongs to the Special Issue The Application of Materials in Modern Manufacturing Processes: Design, Performance and Applied Research)
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15 pages, 7876 KB  
Article
Gas-Sensing Properties of Co9S8 Films Toward Formaldehyde, Ethanol, and Hydrogen Sulfide
by Myeong Gyu Kim and Yun-Hyuk Choi
Materials 2024, 17(23), 5743; https://doi.org/10.3390/ma17235743 - 24 Nov 2024
Viewed by 1178
Abstract
The chemiresistive gas-sensing properties of pristine Co9S8 film are little known despite its potential as a promising gas sensor material due to its intrinsic characteristics. In this study, a pristine polycrystalline Co9S8 film (approximately 440 nm in [...] Read more.
The chemiresistive gas-sensing properties of pristine Co9S8 film are little known despite its potential as a promising gas sensor material due to its intrinsic characteristics. In this study, a pristine polycrystalline Co9S8 film (approximately 440 nm in thickness) is fabricated by depositing a Co3O4 film followed by sulfidation to investigate its gas-sensing properties. The prepared Co9S8 film sensor is found to exhibit high responsiveness towards formaldehyde (HCHO), ethanol (C2H5OH), and hydrogen sulfide (H2S) at operating temperatures of 300 °C and 400 °C, with strong concentration dependence. On the other hand, the sensor shows very low or no responsiveness towards hydrogen (H2), acetone (CH3COCH3), and nitrogen dioxide (NO2). These results enhance our understanding of the intrinsic gas-sensing properties of Co9S8, aiding in the design and fabrication of high-performance chemiresistive gas sensors based on Co9S8. Full article
(This article belongs to the Section Materials Chemistry)
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13 pages, 4061 KB  
Article
Effect of Glycerol Stearates on the Thermal and Barrier Properties of Biodegradable Poly(butylene Adipate-Co-Terephthalate)
by Jing Yuan, Xinpeng Zhang, Jun Xu, Jianping Ding, Wanli Li and Baohua Guo
Materials 2024, 17(23), 5732; https://doi.org/10.3390/ma17235732 - 23 Nov 2024
Cited by 2 | Viewed by 1614
Abstract
Two types of glycerol stearates, glycerol monostearate (GMS) and glycerol tristearate (GTS), were added into poly(butylene adipate-co-terephtalate) (PBAT), with the aim to improve their water vapor barrier properties. The effects of the two small molecules on microstructure, chain mobility, and surface hydrophobicity were [...] Read more.
Two types of glycerol stearates, glycerol monostearate (GMS) and glycerol tristearate (GTS), were added into poly(butylene adipate-co-terephtalate) (PBAT), with the aim to improve their water vapor barrier properties. The effects of the two small molecules on microstructure, chain mobility, and surface hydrophobicity were amply assessed via both experimental and simulation methods. The incorporation of the modifiers at small loadings, 5 wt% of GMS and 1 wt% of GTS, resulted in substantial improvements in water vapor barrier properties, while a further increase in the modifier content resulted in deterioration. The optimal water vapor permeability reached values of 2.63 × 10−13 g·cm/(cm2·s·Pa) and 6.55 × 10−13 g·cm/(cm2·s·Pa), which are substantially lower than the permeability, 8.43 × 10−13 g·cm/(cm2·s·Pa), of neat PBAT. The water vapor permeability of PBAT/GMS blends was also proven to be time-dependent and dramatically decreased with time, mainly due to the migration process of small molecules, forming a waterproof layer. The barrier improvement results are assumed to be related to the hydrophobic effect of glycerol stearate and are largely dependent on the content, polarity, compatibility, and dispersion of modifiers. In addition, the incorporation of modifiers did not largely sacrifice the mechanical strength of PBAT, which is advantageous in mulch film applications. Full article
(This article belongs to the Section Polymeric Materials)
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12 pages, 3497 KB  
Article
Selenium Disulfide from Sustainable Resources: An Example of “Redneck” Chemistry with a Pinch of Salt
by Eduard Tiganescu, Shahrzad Safinazlou, Ahmad Yaman Abdin, Rainer Lilischkis, Karl-Herbert Schäfer, Claudia Fink-Straube, Muhammad Jawad Nasim and Claus Jacob
Materials 2024, 17(23), 5733; https://doi.org/10.3390/ma17235733 - 23 Nov 2024
Cited by 1 | Viewed by 2060
Abstract
Selenium disulfide (often referred to as SeS2) encompasses a family of mixed selenium-sulfide eight-membered rings, traditionally used as an anti-dandruff agent in shampoos. SeS2 can be produced by reacting hydrogen sulfide (H2S) with selenite (SeO32−) [...] Read more.
Selenium disulfide (often referred to as SeS2) encompasses a family of mixed selenium-sulfide eight-membered rings, traditionally used as an anti-dandruff agent in shampoos. SeS2 can be produced by reacting hydrogen sulfide (H2S) with selenite (SeO32−) under acidic conditions. This chemistry is also possible with natural spring waters that are rich in H2S, thus providing an avenue for the more sustainable, green production of high-quality SeS2 particles from an abundant natural source. The orange material obtained this way consists of small globules with a diameter in the range of 1.1 to 1.2 µm composed of various SexS8−x chalcogen rings. It shows the usual composition and characteristics of a Se-S interchalcogen compound in EDX and Raman spectroscopy. Since the mineral water from Bad Nenndorf is also rich in salts, the leftover brine has been evaporated to yield a selenium-enriched salt mixture similar to table salt. As the water from Bad Nenndorf—in comparison to other bodies of water around the world—is still rather modest in terms of its H2S content, especially when compared with volcanic waters, this approach may be refined further to become economically and ecologically viable, especially as a regional business model for small and medium-sized enterprises. Full article
(This article belongs to the Special Issue Novel Green Nanotechnologies Applied in Environmental Protection and Health)
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15 pages, 2341 KB  
Article
Green Synthesis of CuO Nanoparticles—Structural, Morphological, and Dielectric Characterization
by Joana Neiva, Zohra Benzarti, Sandra Carvalho and Susana Devesa
Materials 2024, 17(23), 5709; https://doi.org/10.3390/ma17235709 - 22 Nov 2024
Cited by 13 | Viewed by 2305
Abstract
This study investigates the structural, chemical, and morphological properties of CuO nanoparticles synthesized via a green synthesis route using Opuntia ficus-indica cladode extract, with a focus on the effects of stepwise versus direct calcination. Raman spectroscopy revealed the presence of CuO, [...] Read more.
This study investigates the structural, chemical, and morphological properties of CuO nanoparticles synthesized via a green synthesis route using Opuntia ficus-indica cladode extract, with a focus on the effects of stepwise versus direct calcination. Raman spectroscopy revealed the presence of CuO, Na2CO3, and Na2SO3, with the latter two being associated with elements inherited from the cactus extracts. XRD patterns confirmed the presence of crystalline CuO and Na2CO3 phases, with the low content of Na2SO3 inferred to be amorphous. Rietveld refinement estimated a CuO content of approximately 77% in the stepwise-calcined sample and 75% in the directly calcined sample, with lattice parameters closely aligning with reference values. SEM micrographs revealed a tendency for CuO nanoparticles to aggregate, likely due to high surface energy and interaction with the viscous plant extract used in the green synthesis. Crystallite size estimates, along with morphological observations, suggest that stepwise calcination enhances crystallinity and particle definition without altering the fundamental nanoparticle morphology. These findings highlight the influence of calcination method and natural extracts on the composition and morphology of green-synthesized CuO nanoparticles, offering insights into potential applications, namely in microelectronics, due to their promising dielectric properties. Full article
(This article belongs to the Special Issue Synthesis and Characterization Techniques for Nanomaterials)
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18 pages, 4439 KB  
Article
The Influence of Horsetail (Equisetum arvense L.) Powder and Horsetail-Based Silica on the Crystallization Kinetics of Polylactide
by Olga Mysiukiewicz, Joanna Szulc and Andrzej Miklaszewski
Materials 2024, 17(23), 5697; https://doi.org/10.3390/ma17235697 - 21 Nov 2024
Cited by 1 | Viewed by 1989
Abstract
Biogenic silica (SiO2) sourced from living organisms, especially plants such as rice and other cereals, has recently been successfully applied in different polymeric compositions. Another rich source of biogenic silica is common horsetail (Equisetum arvense L.), containing up to 25% [...] Read more.
Biogenic silica (SiO2) sourced from living organisms, especially plants such as rice and other cereals, has recently been successfully applied in different polymeric compositions. Another rich source of biogenic silica is common horsetail (Equisetum arvense L.), containing up to 25% SiO2 in the dry matter. In this study, biogenic silica was obtained from horsetail powder by acid leaching in sulfuric acid and calcination at 400 °C. The analysis, including measurements of specific surface area using the Brunauer–Emmett–Teller method, assessment of crystallinity by X-ray diffraction, as well as chemical content analysis by Fourier-transform infrared spectroscopy showed that high-purity, high-surface mesoporous silica was obtained. The biogenic silica and horsetail powders were also introduced to polylactide (PLA) to determine their influence on the polymer’s crystallization, which was studied in both non-isothermal and isothermal conditions by differential scanning calorimetry. The crystallization parameters were calculated according to the Avrami method based on isothermal crystallization curves at 100, 110 and 120 °C. The crystalline structures were observed by optical microscopy in polarized light. It was found that both fillers improve the crystallization of PLA, especially in low-supercooling conditions, so they can be successfully utilized in industrial applications, when high crystallinity of polylactide is needed. Full article
(This article belongs to the Special Issue Advanced Designs of Materials, Machines and Processes in a Circular Economy)
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21 pages, 3260 KB  
Article
Amber “Alchemy”: Recreating and Investigating Yellow Glass Formulations
by Catarina Reis Santos, Andreia Ruivo, Ana Carneiro, João Pedro Veiga, Teresa Palomar and Inês Coutinho
Materials 2024, 17(23), 5699; https://doi.org/10.3390/ma17235699 - 21 Nov 2024
Viewed by 1526
Abstract
Amber glass has been produced since at least the 6th century BC. Its value derives from its ability to mimic natural amber and, later, from its ultraviolet filtering properties. Until the 19th century, amber glass was widely used for the storage of food [...] Read more.
Amber glass has been produced since at least the 6th century BC. Its value derives from its ability to mimic natural amber and, later, from its ultraviolet filtering properties. Until the 19th century, amber glass was widely used for the storage of food and medicines because its protective properties had been empirically recognized. This study investigates historical methods of amber glass production by using glass recipes from four Portuguese arcana (1793–1975) and focusing on Fe-S and Fe-Mn chromophores. Five recipes were reproduced under controlled laboratory conditions, resulting in 21 experiments. Of these, only 10 produced amber glasses were with different shades. Chemical compositions were analysed by WDXRF, while DSC and dilatometry were used to assess thermal properties. Vickers hardness tests and UV–visible absorption spectroscopy provided insight into mechanical strength and chromophore presence. The study found that FeS amber glass was more difficult to produce than Fe-Mn amber glass, given the complex variables involved in the former, such as SO3 volatility affecting the final product. Reproduction of historical recipes showed that, even without modern chemical knowledge, historical glassmakers developed practical, empirical methods for making amber glass. These findings contribute to a broader understanding of glass conservation and highlight the importance of historical glass recipes for the interpretation and conservation of glass objects. Full article
(This article belongs to the Special Issue Materials in Cultural Heritage: Analysis, Testing, and Preservation)
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14 pages, 23867 KB  
Article
Solid-State Synthesis for High-Tetragonality, Small-Particle Barium Titanate
by Tianyu Hao, Jing Shen, Qiaochu Peng, Jie Liu, Wenbin Hu and Cheng Zhong
Materials 2024, 17(22), 5655; https://doi.org/10.3390/ma17225655 - 20 Nov 2024
Cited by 3 | Viewed by 2094
Abstract
This study successfully synthesized high-tetragonality barium titanate (BaTiO3) particles with a small particle size by implementing ball milling in the solid-state synthesis of BaTiO3 and utilizing nanoscale raw materials. This study also addressed the issues of impurities and uneven particle [...] Read more.
This study successfully synthesized high-tetragonality barium titanate (BaTiO3) particles with a small particle size by implementing ball milling in the solid-state synthesis of BaTiO3 and utilizing nanoscale raw materials. This study also addressed the issues of impurities and uneven particle size distribution that could exist in the synthesized BaTiO3 particles. The crystal structure, morphology, and particle size of the synthesized BaTiO3 particles have been meticulously analyzed and discussed through the use of techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and the laser particle size analyzer. BaTiO3 has been successfully synthesized, exhibiting a uniform particle size with an average diameter of 170 nm and a high tetragonality value of 1.01022. This new solid-state synthesis method provided insights to avoid the impact of “size effects” during the process of electronic device miniaturization. Full article
(This article belongs to the Special Issue Feature Papers in Refractories and Ceramics: Microstructure, Properties and Applications (3rd Edition))
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13 pages, 5400 KB  
Article
Exploring Light Stability and Trapping Mechanisms in Organic Thin-Film Transistors for High-Brightness MicroLED Integration
by Chia-Hung Tsai, Yang-En Wu, Chuan-Wei Kuo, Ting-Chang Chang, Li-Yin Chen, Fang-Chung Chen and Hao-Chung Kuo
Materials 2024, 17(22), 5643; https://doi.org/10.3390/ma17225643 - 19 Nov 2024
Cited by 3 | Viewed by 1354
Abstract
Organic thin-film transistors (OTFTs), benefiting from a low-temperature process (≤120 °C), offer a promising approach for the monolithic integration of MicroLED structures through organic-last integration. Previous research has demonstrated that small-molecule/polymer binder-based organic semiconductor deposition, utilizing the vertical phase separation mechanism, can achieve [...] Read more.
Organic thin-film transistors (OTFTs), benefiting from a low-temperature process (≤120 °C), offer a promising approach for the monolithic integration of MicroLED structures through organic-last integration. Previous research has demonstrated that small-molecule/polymer binder-based organic semiconductor deposition, utilizing the vertical phase separation mechanism, can achieve good device uniformity while preserving high field-effect carrier mobility. However, the stability of OTFTs under light exposure at the device level remains underexplored. This study investigates the effects of various light irradiation conditions on OTFTs and delves into the underlying mechanisms of the light-trapping effect. Based on these findings, we propose an optimal OTFT design tailored for driving MicroLED displays at high operational brightness, ensuring both performance and stability. Full article
(This article belongs to the Special Issue Advanced Materials for Organic Semiconductors and Their Applications)
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19 pages, 3453 KB  
Review
Opportunities and Challenges for Predicting the Service Status of SLM Metal Parts Under Big Data and Artificial Intelligence
by Xiaoling Yan and Huiwen Fu
Materials 2024, 17(22), 5648; https://doi.org/10.3390/ma17225648 - 19 Nov 2024
Viewed by 1369
Abstract
Selective laser melting (SLM) technology is a high-end dual-use technology that is implemented in aerospace and medical equipment, as well as the automotive industry and other military and civilian industries, and is urgently needed for major equipment manufacturing and national defense industries. This [...] Read more.
Selective laser melting (SLM) technology is a high-end dual-use technology that is implemented in aerospace and medical equipment, as well as the automotive industry and other military and civilian industries, and is urgently needed for major equipment manufacturing and national defense industries. This paper examines the challenges of uncontrollable service states and the inability to ensure service safety of SLM metal parts under nonlinear and complex operating conditions. An overview of the prediction of the service status of SLM metal parts was introduced, and an effective approach solving the problem was provided in this paper. In this approach, the cross-scale coupling mechanism between mesoscopic damage evolution and macroscopic service state evolution is clarified by tracking the mesoscopic damage evolution process of SLM metal parts based on ultrasonic nonlinear responses. The failure mechanism is organically integrated with hidden information from monitoring big data, and a “chimeric” model to accurately evaluate the service status of SLM metal parts is constructed. Combining nonlinear ultrasound technology with big data and artificial intelligence to construct a “chimeric” model and consummate the corresponding methods and theories for evaluating the service status of SLM metal parts is an effective way to reveal the mesoscopic damage evolution and service status evolution mechanisms of SLM metal parts under complex factor coupling, and to accurately describe and characterize the service status of parts under complex operating conditions. The proposed approach will provide a theoretical basis and technical guarantee for the precise management of SLM parts’ service safety in key equipment fields such as aerospace, medical equipment, and the automotive industry. Full article
(This article belongs to the Section Advanced Materials Characterization)
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25 pages, 5749 KB  
Article
A Statistical Assessment of Drilling Effects on Glass Fiber-Reinforced Polymeric Composites
by Ana Martins, Alda Carvalho, Ivo M. F. Bragança, Inês C. J. Barbosa, Joaquim Infante Barbosa and Maria A. R. Loja
Materials 2024, 17(22), 5631; https://doi.org/10.3390/ma17225631 - 18 Nov 2024
Cited by 1 | Viewed by 1139
Abstract
Fiber-reinforced composites are extensively used in many components and structures in various industry sectors, and the need to connect and assemble such types of components may require drilling operations. Although drilling is a common machining process; when dealing with fiber-reinforced composite materials, additional [...] Read more.
Fiber-reinforced composites are extensively used in many components and structures in various industry sectors, and the need to connect and assemble such types of components may require drilling operations. Although drilling is a common machining process; when dealing with fiber-reinforced composite materials, additional and specific problems may arise that can com-promise mechanical integrity. So, the main goal of this work is to assess how various input variables impact two main outcomes in the drilling process: the exit-adjusted delamination factor and the maximum temperature on the bottom surface where the drilling tool exits. The input variables include the type of drilling tools used, the operating speeds, and the thickness of the plates being drilled. By using Analysis of Variance (ANOVA), the analysis aims to identify which factors significantly influence damage and exit temperature. The results demonstrate that the influence of tools and drilling parameters is critical, and those selections impact the quality of the hole and the extent of the induced damage to the surrounding area. In concrete, considering the initially selected set of tools, the BZT03 tool does not lead to high-quality holes when drilling medium- and high-thickness plates. In contrast, the Dagger tool shows potential to reduce exit hole damage while also lowering temperature. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Materials and Parts: Techniques, Case Studies and Practical Applications)
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24 pages, 2964 KB  
Review
Cavitation and Solid-State Post-Condensation of Polyethylene Terephthalate: Literature Review
by Paweł Wawrzyniak, Waldemar Karaszewski and Artur Różański
Materials 2024, 17(22), 5637; https://doi.org/10.3390/ma17225637 - 18 Nov 2024
Cited by 3 | Viewed by 1710
Abstract
Polyethylene terephthalate (PET) is widely used in bottle production by stretch blow molding processes (SBM processes) due to its cost-effectiveness and low environmental impact. The presented literature review focuses on microcavitation and solid-state post-condensation effects that occur during the deformation of PET in [...] Read more.
Polyethylene terephthalate (PET) is widely used in bottle production by stretch blow molding processes (SBM processes) due to its cost-effectiveness and low environmental impact. The presented literature review focuses on microcavitation and solid-state post-condensation effects that occur during the deformation of PET in the SBM process. The literature review describes cavitation and microcavitation effects in PET material and solid-state post-condensation of PET on the basis of a three-phase model of the PET microstructure. A three-phase model of PET microstructure (representing the amorphous phase in two ways, depending on the ratio of the trans-to-gauche conformation of the PET macromolecule and the amount of free volume) with a nucleation process, a crystallization process, and the use of positron annihilation lifetime spectroscopy (PALS) to analyze PET microstructure are discussed in detail. The conceptual model developed based on the literature combines solid-state post-condensation with microcavitation via the diffusion of the post-condensation product. This review identifies the shortcomings of the developed conceptual model and presents them with five hypotheses, which will be the basis for further research. Full article
(This article belongs to the Special Issue Multiphase Systems with Polymeric Matrices: Polymer Blends and Composites II)
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11 pages, 3705 KB  
Article
Zirconium Oxide as a Novel Material for Post-Endodontically Treated Teeth: Comparative Fracture Behavior of 3D-Printed Cobalt–Chromium, Milled Zirconium Oxide, and Quartz Fiber Posts
by Armin Sokolowski, Fernando Gustavo Warchomicka, Lukas Seebacher, Bernhard Remschmidt, Marcus Rieder, Lumnije Kqiku-Biblekaj and Alwin Sokolowski
Materials 2024, 17(22), 5611; https://doi.org/10.3390/ma17225611 - 17 Nov 2024
Viewed by 1672
Abstract
This study evaluates the mechanical properties of materials used in the post-endodontic restoration of root-treated teeth and examines their performance under stress to provide insights for material selection in clinical applications. Particular attention is given to zirconium oxide, which demonstrates promising characteristics due [...] Read more.
This study evaluates the mechanical properties of materials used in the post-endodontic restoration of root-treated teeth and examines their performance under stress to provide insights for material selection in clinical applications. Particular attention is given to zirconium oxide, which demonstrates promising characteristics due to its esthetic color and favorable material properties, positioning it as a potential material for future use in post-endodontic treatments. Three materials—prefabricated quartz fiber-reinforced composite, milled zirconium oxide, and additively manufactured cobalt–chromium—were evaluated using compressive-deflection tests. The specimens were subjected to a 45° compressive load extending 5 mm from a metal core. Their mechanical properties were analyzed using one-way ANOVA and Tukey’s post hoc test. Significant differences were observed among the materials. Quartz fiber posts, with the lowest force resistance, buckled at lower loads (143.3 ± 9.9 N), while zirconia posts failed in a brittle manner at higher forces (246.1 ± 97.2 N). Cobalt–chromium posts demonstrated the highest maximal force (323.2 ± 10.5 N, p < 0.001) and, unlike the other materials, bent rather than fractured. The failure patterns of the tested materials underscore the importance of careful material selection when restoring root-treated teeth. Despite displaying distinct fracture characteristics, zirconium oxide, due to its color, rigidity, and hardness, stands out as a promising material for future dental applications. Further research through randomized clinical trials is recommended to refine treatment approaches and optimize clinical outcomes. Full article
(This article belongs to the Special Issue Recent Research in Restorative Dental Materials)
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18 pages, 5642 KB  
Article
A New Slicer-Based Method to Generate Infill Inspired by Sandwich-Patterns for Reduced Material Consumption
by Patrick Steck, Dominik Schuler, Christian Witzgall and Sandro Wartzack
Materials 2024, 17(22), 5596; https://doi.org/10.3390/ma17225596 - 15 Nov 2024
Viewed by 1474
Abstract
This work presents a novel infill method for additive manufacturing, specifically designed to optimize material use and enhance stiffness in fused filament fabrication (FFF) parts through a geometry-aware, corrugated design inspired by sandwich structures. Unlike standard infill patterns, which typically employ uniform, space-filling [...] Read more.
This work presents a novel infill method for additive manufacturing, specifically designed to optimize material use and enhance stiffness in fused filament fabrication (FFF) parts through a geometry-aware, corrugated design inspired by sandwich structures. Unlike standard infill patterns, which typically employ uniform, space-filling grids that often disregard load-specific requirements, this method generates a cavity inside the component to be printed and fill the space between inner and outer contours with continuous, adaptable extrusion paths. This design enables consistent support and improved load distribution, making it particularly effective for parts under bending stresses, as it enhances structural resilience without requiring additional material. Simulations performed on a 10 cm3 test part using this method showed potential reductions in material consumption by up to 77% and a decrease in print time by 78%, while maintaining stiffness comparable to parts using conventional 100% grid infill. Additionally, simulations demonstrated that the new corrugated infill pattern provides near-isotropic stiffness, addressing the anisotropic limitations often seen in traditional infill designs that are sensitive to load orientation. This geometry-aware infill strategy thus contributes to balanced stiffness across complex geometries, enhancing reliability under mechanical loads. By integrating directly with slicer software, this approach simplifies advanced stiffness optimization without the necessity of finite element analysis-based topology optimization. Full article
(This article belongs to the Special Issue Advanced Additive Manufacturing and Application)
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22 pages, 3147 KB  
Review
Biocomposite Scaffolds for Tissue Engineering: Materials, Fabrication Techniques and Future Directions
by Naznin Sultana, Anisa Cole and Francine Strachan
Materials 2024, 17(22), 5577; https://doi.org/10.3390/ma17225577 - 15 Nov 2024
Cited by 15 | Viewed by 3996
Abstract
Tissue engineering is an interdisciplinary field that combines materials, methods, and biological molecules to engineer newly formed tissues to replace or restore functional organs. Biomaterials-based scaffolds play a crucial role in developing new tissue by interacting with human cells. Tissue engineering scaffolds with [...] Read more.
Tissue engineering is an interdisciplinary field that combines materials, methods, and biological molecules to engineer newly formed tissues to replace or restore functional organs. Biomaterials-based scaffolds play a crucial role in developing new tissue by interacting with human cells. Tissue engineering scaffolds with ideal characteristics, namely, nontoxicity, biodegradability, and appropriate mechanical and surface properties, are vital for tissue regeneration applications. However, current biocomposite scaffolds face significant limitations, particularly in achieving structural durability, controlled degradation rates, and effective cellular integration. These qualities are essential for maintaining long-term functionality in vivo. Although commonly utilized biomaterials can provide physical and chemical properties needed for tissue regeneration, inadequate biomimetic properties, as well as insufficient interactions of cells-scaffolds interaction, still need to be improved for the application of tissue engineering in vivo. It is impossible to achieve some essential features using a single material, so combining two or more materials may accomplish the requirements. In order to achieve a proper scaffold design, a suitable fabrication technique and combination of biomaterials with controlled micro or nanostructures are needed to achieve the proper biological responses. This review emphasizes advancements in scaffold durability, biocompatibility, and cellular responsiveness. It focuses on natural and synthetic polymer combinations and innovative fabrication techniques. Developing stimulus-responsive 3D scaffolds is critical, as these scaffolds enhance cell adhesion and promote functional tissue formation while maintaining structural integrity over time. This review also highlights the natural polymers, smart materials, and recent advanced techniques currently used to create emerging scaffolds for tissue regeneration applications. Full article
(This article belongs to the Special Issue Advances in Functional Soft Materials—2nd Volume)
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26 pages, 19332 KB  
Article
Polylactide Composites Reinforced with Pre-Impregnated Natural Fibre and Continuous Cellulose Yarns for 3D Printing Applications
by Lakshmi Priya Muthe, Kim Pickering and Christian Gauss
Materials 2024, 17(22), 5554; https://doi.org/10.3390/ma17225554 - 14 Nov 2024
Cited by 4 | Viewed by 1761
Abstract
Achieving high-performance 3D printing composite filaments requires addressing challenges related to fibre wetting and uniform fibre/polymer distribution. This study evaluates the effectiveness of solution (solvent-based) and emulsion (water-based) impregnation techniques to enhance fibre wetting in bleached flax yarns by polylactide (PLA). For the [...] Read more.
Achieving high-performance 3D printing composite filaments requires addressing challenges related to fibre wetting and uniform fibre/polymer distribution. This study evaluates the effectiveness of solution (solvent-based) and emulsion (water-based) impregnation techniques to enhance fibre wetting in bleached flax yarns by polylactide (PLA). For the first time, continuous viscose yarn composites were also produced using both impregnation techniques. All the composites were carefully characterised throughout each stage of production. Initially, single yarns were impregnated and consolidated to optimise formulations and processing parameters. Solution impregnation resulted in the highest tensile strength (356 MPa) for PLA/bleached flax filaments, while emulsion impregnation yielded the highest tensile strength for PLA/viscose filaments (255 MPa) due to better fibre wetting and fibre distribution. Impregnated single yarns were then combined, with additional polymer added to produce filaments compatible with standard material extrusion 3D printers. Despite a reduction in the mechanical performance of the 3D-printed composites due to additional polymer impregnation, relatively high tensile and bending strengths were achieved, and the Charpy impact strength (>127 kJ/m2) for the viscose-based composite exceeded the reported values for bio-derived fibre reinforced composites. The robust mechanical performance of these filaments offers new opportunities for the large-scale additive manufacturing of structural components from bio-derived and renewable resources. Full article
(This article belongs to the Section Polymeric Materials)
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13 pages, 7008 KB  
Article
Si Characterization on Thinning and Singulation Processes for 2.5/3D HBM Package Integration
by MiKyeong Choi, SeaHwan Kim, TaeJoon Noh, DongGil Kang and SeungBoo Jung
Materials 2024, 17(22), 5529; https://doi.org/10.3390/ma17225529 - 13 Nov 2024
Viewed by 2089
Abstract
As stacking technologies, such as 2.5D and 3D packages, continue to accelerate in advanced semiconductor components, the singulation and thinning of Si wafers are becoming increasingly critical. Despite their importance in producing thinner and more reliable Si chips, achieving high reliability remains a [...] Read more.
As stacking technologies, such as 2.5D and 3D packages, continue to accelerate in advanced semiconductor components, the singulation and thinning of Si wafers are becoming increasingly critical. Despite their importance in producing thinner and more reliable Si chips, achieving high reliability remains a challenge, and comprehensive research on the effects of these processing techniques on Si chip integrity is lacking. In this study, the impacts of wafer thinning and singulation on the fracture strength of Si wafers were systematically compared. Three different grinding processes, namely fine grinding, poly-grinding, and polishing, were used for thinning, and the resulting surface morphology and roughness were analyzed using scanning electron microscopy and an interferometer. In addition, the residual mechanical stress on the wafer surface was measured using Raman spectroscopy. The fracture strength of Si wafers and chips was assessed through three-point bending tests. Singulation, including blade dicing, laser dicing, and stealth dicing, was evaluated for its impact on fracture strength. Among these processes, polishing for wafer thinning exhibited the lowest full-width half maximum and intensity ratio of Raman shifts (I480/I520), indicating minimal residual stress and surface defects. Consequently, Si wafers and chips processed through polishing demonstrated the highest fracture strength. Moreover, the 60 µm thick Si wafers and chips showed the highest fracture strength compared with those with thicknesses of 90 and 120 µm, possibly because of the increased flexibility, which mitigates stress. Among the singulation methods, stealth dicing yielded the highest fracture strength, outperforming blade and laser dicing. The combination of wafer thinning via polishing and singulation via stealth dicing presents an optimal solution for producing highly reliable Si chips for 2.5D and 3D packaging. These findings may be valuable in selecting optimal processing technologies for high-reliability Si chip production in industrial settings. Full article
(This article belongs to the Section Advanced Materials Characterization)
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16 pages, 2999 KB  
Article
Modification of Poly(3-Hydroxybutyrate) with a Linear Polyurethane Modifier and Organic Nanofiller—Preparation and Structure–Property Relationship
by Iwona Zarzyka, Beata Krzykowska, Karol Hęclik, Wiesław Frącz, Grzegorz Janowski, Łukasz Bąk, Tomasz Klepka, Jarosław Bieniaś, Monika Ostapiuk, Aneta Tor-Świątek, Magda Droździel-Jurkiewicz, Adam Tomczyk, Anna Falkowska and Michał Kuciej
Materials 2024, 17(22), 5542; https://doi.org/10.3390/ma17225542 - 13 Nov 2024
Cited by 2 | Viewed by 1151
Abstract
The growing demand for products made of polymeric materials, including the commonly used polypropylene (PP), is accompanied by the problem of storing and disposing of non-biodegradable waste, increasing greenhouse gas emissions, climate change and the creation of toxic products that constitute a health [...] Read more.
The growing demand for products made of polymeric materials, including the commonly used polypropylene (PP), is accompanied by the problem of storing and disposing of non-biodegradable waste, increasing greenhouse gas emissions, climate change and the creation of toxic products that constitute a health hazard of all living organisms. Moreover, most of the synthetic polymers used are made from petrochemical feedstocks from non-renewable resources. The use of petrochemical raw materials also causes degradation of the natural environment. A potential solution to these problems is the use of biopolymers. Biopolymers include biodegradable or biosynthesizable polymers, i.e., obtained from renewable sources or produced synthetically but from raw materials of natural origin. One of them is the poly(3-hydroxybutyrate) (P3HB) biopolymer, whose properties are comparable to PP. Unfortunately, it is necessary to modify its properties to improve its processing and operational properties. In the work, hybrid polymer nanobiocomposites based on P3HB, with the addition of chain, uncross-linked polyurethane (PU) and layered aluminosilicate modified with organic salts (Cloisite®30B) were produced by extrusion process. The introduction of PU and Cloisite®30B to the polymer matrix (P3HB) influenced the processing parameters beneficially and resulted in a decrease in the extrusion temperature of more than 10 °C. The influence of the simultaneous addition of a constant amount of PU (10 m/m%) and the different amounts of nanoadditives (1, 2 and 3 m/m%) on the compatibility, morphology and static mechanical properties of the resulted nanobiocomposites were examined. The component interactions by Fourier transformation infrared spectroscopy (FTIR) analysis, nano- and microscale structure studies using small-angle X-ray scattering (SAXS) and morphology by scanning electron microscopy (SEM) were carried out, and the hardness and tensile strength of the obtained polymer nanobiocomposites were determined. FTIR analysis identified the compatibility of the polyester matrix, PU, and organomodified montmorillonite, the greatest being 3 m/m% Cloisite30B content. The addition of PU to the polyester elasticizes the material and decreases the material’s strength and ductility. The presence of nanoclay enhanced the mechanical properties of nanobiocomposites. The resulting nanobiocomposites can be used in the production of short-life materials applied in gardening or agriculture. Full article
(This article belongs to the Special Issue Progressive Technologies and Materials in Mechanical and Materials Engineering)
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26 pages, 16106 KB  
Article
Physicochemical Characterization and Kinetics Study of Polymer Carriers with Vitamin C for Controlled Release Applications
by Magdalena Bańkosz
Materials 2024, 17(22), 5502; https://doi.org/10.3390/ma17225502 - 12 Nov 2024
Cited by 5 | Viewed by 1527
Abstract
This study focuses on the selection and evaluation of a kinetic model for the release of vitamin C from different delivery systems, including microcapsules, hydrogels, and a hybrid system combining both. The microcapsules were synthesized from a 2% sodium alginate solution and with [...] Read more.
This study focuses on the selection and evaluation of a kinetic model for the release of vitamin C from different delivery systems, including microcapsules, hydrogels, and a hybrid system combining both. The microcapsules were synthesized from a 2% sodium alginate solution and with vitamin C incorporated in selected formulations. Hydrogels were obtained through photopolymerization using poly(ethylene glycol) diacrylate and polyvinyl alcohol, with and without the addition of vitamin C. The hybrid system incorporated the vitamin C-containing microcapsules within the hydrogel matrix. Physicochemical properties, such as density, porosity, and water vapor transmission rate (WVTR), were evaluated. Kinetic studies of vitamin C release were conducted under dynamic and static conditions, and the experimental data were fitted to six different kinetic models: zero-order, first-order, second-order, Higuchi, Korsmeyer–Peppas, and Hixson–Crowell. The Higuchi and Korsmeyer–Peppas models provided the best fit for most systems, indicating that the release is predominantly controlled by diffusion and, in dynamic conditions, swelling of the matrix. The hybrid system, while exhibiting slower release than the microcapsules and hydrogel alone, demonstrated more controlled and sustained release, which is advantageous for applications requiring prolonged action. Full article
(This article belongs to the Special Issue Research of Organic Molecules and Materials for Biological Application)
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18 pages, 2541 KB  
Review
Determining the Permeability of Porous Bioceramic Scaffolds: Significance, Overview of Current Methods and Challenges Ahead
by Roberta Gabrieli, Alessandro Schiavi and Francesco Baino
Materials 2024, 17(22), 5522; https://doi.org/10.3390/ma17225522 - 12 Nov 2024
Cited by 6 | Viewed by 1628
Abstract
The “architectural suitability” of scaffolds for bone tissue engineering is commonly evaluated by assessing the pore volume and the mean pore size (or pore size distribution, if possible) and comparing these values with the reference ranges of human cancellous bone. However, these two [...] Read more.
The “architectural suitability” of scaffolds for bone tissue engineering is commonly evaluated by assessing the pore volume and the mean pore size (or pore size distribution, if possible) and comparing these values with the reference ranges of human cancellous bone. However, these two parameters cannot precisely describe the complex architecture of bone scaffolds and just provide a preliminary comparative criterion. Permeability is suggested as a more comprehensive and significant parameter to characterize scaffold architecture and mass transport capability, being also related to bone in-growth and, thus, functional properties. However, assessing the permeability of bioactive ceramics and glass scaffolds is a complex task from both methodological and experimental viewpoints. After providing an overview of the fundamentals about porosity in scaffolds, this review explores the different experimental and numerical approaches used to determine the permeability of porous bioceramics, describing the methodologies used (pump-based, gravity-based, acoustic and computational methods) and highlighting advantages and limitations to overcome (e.g., reliability issues and need for better standardization of the experimental procedures). Full article
(This article belongs to the Special Issue Porous Ceramics, Glasses and Composites, Volume II)
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39 pages, 8550 KB  
Review
Enhancement of Magnetic Shielding Based on Low-Noise Materials, Magnetization Control, and Active Compensation: A Review
by Yijin Liu, Jianzhi Yang, Fuzhi Cao, Xu Zhang and Shiqiang Zheng
Materials 2024, 17(22), 5469; https://doi.org/10.3390/ma17225469 - 8 Nov 2024
Cited by 10 | Viewed by 5918
Abstract
Magnetic-shielding technologies play a crucial role in the field of ultra-sensitive physical measurement, medical imaging, quantum sensing, etc. With the increasing demand for the accuracy of magnetic measurement, the performance requirements of magnetic-shielding devices are also higher, such as the extremely weak magnetic [...] Read more.
Magnetic-shielding technologies play a crucial role in the field of ultra-sensitive physical measurement, medical imaging, quantum sensing, etc. With the increasing demand for the accuracy of magnetic measurement, the performance requirements of magnetic-shielding devices are also higher, such as the extremely weak magnetic field, gradient, and low-frequency noise. However, the conventional method to improve the shielding performance by adding layers of materials is restricted by complex construction and inherent materials noise. This paper provides a comprehensive review about the enhancement of magnetic shielding in three aspects, including low-noise materials, magnetization control, and active compensation. The generation theorem and theoretical calculation of materials magnetic noise is summarized first, focusing on the development of spinel ferrites, amorphous, and nanocrystalline. Next, the principles and applications of two magnetization control methods, degaussing and magnetic shaking, are introduced. In the review of the active magnetic compensation system, the forward and inverse design methods of coil and the calculation method of the coupling effect under the ferromagnetic boundary of magnetic shield are explained in detail, and their applications, especially in magnetocardiography (MCG) and magnetoencephalogram (MEG), are also mainly described. In conclusion, the unresolved challenges of different enhancement methods in materials preparation, optimization of practical implementation, and future applications are proposed, which provide comprehensive and instructive references for corresponding research. Full article
(This article belongs to the Special Issue Preparation, Electromagnetic Absorption and Shielding Properties of Electromagnetic Functional Materials)
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22 pages, 3931 KB  
Review
Securing Rare Earth Permanent Magnet Needs for Sustainable Energy Initiatives
by Dan-Cristian Popa and Loránd Szabó
Materials 2024, 17(22), 5442; https://doi.org/10.3390/ma17225442 - 7 Nov 2024
Cited by 8 | Viewed by 3472
Abstract
Rare earth permanent magnets are vital in various sectors, including renewable energy conversion, where they are widely used in permanent magnet generators. However, the global supply and availability of these materials present significant risks, and their mining and processing have raised serious environmental [...] Read more.
Rare earth permanent magnets are vital in various sectors, including renewable energy conversion, where they are widely used in permanent magnet generators. However, the global supply and availability of these materials present significant risks, and their mining and processing have raised serious environmental concerns. This paper reviews the necessary legislative, economic, and technological measures that must be implemented to address these issues. While it may not be feasible to eliminate the risks associated with the availability of rare earth materials, researchers in the field of electrical generators can play a crucial role in significantly reducing the demand for newly mined and processed such materials, thereby mitigating the negative environmental impacts of their extraction and production. Full article
(This article belongs to the Special Issue Advances in Sustainable Energy Materials and Devices)
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26 pages, 21893 KB  
Article
An Example of Using Low-Cost LiDAR Technology for 3D Modeling and Assessment of Degradation of Heritage Structures and Buildings
by Piotr Kędziorski, Marcin Jagoda, Paweł Tysiąc and Jacek Katzer
Materials 2024, 17(22), 5445; https://doi.org/10.3390/ma17225445 - 7 Nov 2024
Cited by 3 | Viewed by 1568
Abstract
This article examines the potential of low-cost LiDAR technology for 3D modeling and assessment of the degradation of historic buildings, using a section of the Koszalin city walls in Poland as a case study. Traditional terrestrial laser scanning (TLS) offers high accuracy but [...] Read more.
This article examines the potential of low-cost LiDAR technology for 3D modeling and assessment of the degradation of historic buildings, using a section of the Koszalin city walls in Poland as a case study. Traditional terrestrial laser scanning (TLS) offers high accuracy but is expensive. The study assessed whether more accessible LiDAR options, such as those integrated with mobile devices such as the Apple iPad Pro, can serve as viable alternatives. This study was conducted in two phases—first assessing measurement accuracy and then assessing degradation detection—using tools such as the FreeScan Combo scanner and the Z+F 5016 IMAGER TLS. The results show that, while low-cost LiDAR is suitable for small-scale documentation, its accuracy decreases for larger, complex structures compared to TLS. Despite these limitations, this study suggests that low-cost LiDAR can reduce costs and improve access to heritage conservation, although further development of mobile applications is recommended. Full article
(This article belongs to the Special Issue Advanced Materials & Methods for Heritage & Archaeology (Second Edition))
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10 pages, 2301 KB  
Article
Fibrillated Films for Suspension Catalyst Immobilization—A Kinetic Study of the Nitrobenzene Hydrogenation
by Chiara Boscagli, Enrico Lepre, Oliver Hofmann, Lukas Wengeler, Marcel Schmitt, Ivana Jevtovikj, Carlos Lizandara-Pueyo and Stephan A. Schunk
Materials 2024, 17(22), 5411; https://doi.org/10.3390/ma17225411 - 6 Nov 2024
Viewed by 1157
Abstract
The immobilization of suspension catalysts in flexible, fibrillated films offers a promising solution to the mass transfer limitations often encountered in three-phase hydrogenation reactions. This study investigates the catalytic performance and mass transfer properties of fibrillated films in the hydrogenation of nitrobenzene to [...] Read more.
The immobilization of suspension catalysts in flexible, fibrillated films offers a promising solution to the mass transfer limitations often encountered in three-phase hydrogenation reactions. This study investigates the catalytic performance and mass transfer properties of fibrillated films in the hydrogenation of nitrobenzene to aniline, comparing them to free-flowing powdered catalysts. Fibrillated films were prepared from Pd/C catalysts with varying thicknesses (100–400 µm), and their performance was evaluated through kinetic studies in both batch reactors and microreactors. The specific activity of the films was significantly influenced by film thickness with thinner films demonstrating lower mass transfer limitations. However, mass transfer limitations were observed in thicker films, prompting the development of alternative film designs, including enhanced macro-porous films and sandwich structures. These modifications successfully minimized diffusion limitations, achieving similar specific activity to the powder catalysts while maintaining the mechanical stability of the films. This work demonstrates the feasibility of using fibrillated films for continuous catalytic processes and highlights their potential for efficient catalyst reuse, avoiding filtration steps and enhancing process sustainability. Furthermore, while PTFE remains indispensable for producing such films due to its mechanical and thermal stability, ongoing research focuses on identifying more environmentally friendly alternatives without compromising performance. Full article
(This article belongs to the Special Issue Recent Developments in Catalytic Materials)
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14 pages, 6179 KB  
Article
Preparation and Characterization of Mechanical Properties of HAP/45S5 Bioglass Laminated Ceramic Composites via Spark Plasma Sintering
by Ye Meng, Xinge Li and Bing Yun
Materials 2024, 17(22), 5413; https://doi.org/10.3390/ma17225413 - 6 Nov 2024
Cited by 2 | Viewed by 1638
Abstract
Hydroxyapatite (HAP) displays a high degree of similarity to the inorganic components that make up roughly 70% of human hard tissue, and it possesses exceptional biological activity and biocompatibility. It is currently internationally recognized as the most biologically active hard tissue implant material. [...] Read more.
Hydroxyapatite (HAP) displays a high degree of similarity to the inorganic components that make up roughly 70% of human hard tissue, and it possesses exceptional biological activity and biocompatibility. It is currently internationally recognized as the most biologically active hard tissue implant material. However, its substandard mechanical properties have significantly limited the application of HAP in areas requiring load bearing or in the repair of large bone defects. In this study, HAP/45S5 bioglass laminated ceramic composites were consolidated using the spark plasma sintering (SPS) technique. The grain growth and phase transformation of HAP and 45S5 bioglass were examined at various sintering temperatures. The mechanical properties of the laminated composites were investigated. At 950 °C, the flexural strength and fracture work of the sintered body were (153.22 ± 7.7) MPa and (2049 ± 34) J·m−2, respectively. These results corresponded to the load–displacement curves and showed that the composites met the mechanical performance requirements of the support material. Full article
(This article belongs to the Section Advanced and Functional Ceramics and Glasses)
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21 pages, 1766 KB  
Review
Advanced Biomaterials for Lacrimal Tissue Engineering: A Review
by Kevin Y. Wu, Archan Dave, Patrick Daigle and Simon D. Tran
Materials 2024, 17(22), 5425; https://doi.org/10.3390/ma17225425 - 6 Nov 2024
Cited by 2 | Viewed by 2890
Abstract
The lacrimal gland (LG) is vital for ocular health, producing tears that lubricate and protect the eye. Dysfunction of the LG leads to aqueous-deficient dry eye disease (DED), significantly impacting quality of life. Current treatments mainly address symptoms rather than the underlying LG [...] Read more.
The lacrimal gland (LG) is vital for ocular health, producing tears that lubricate and protect the eye. Dysfunction of the LG leads to aqueous-deficient dry eye disease (DED), significantly impacting quality of life. Current treatments mainly address symptoms rather than the underlying LG dysfunction, highlighting the need for regenerative therapies. Tissue engineering offers a promising solution, with biomaterials playing crucial roles in scaffolding and supporting cell growth for LG regeneration. This review focuses on recent advances in biomaterials used for tissue engineering of the lacrimal gland. We discuss both natural and synthetic biomaterials that mimic the extracellular matrix and provide structural support for cell proliferation and differentiation. Natural biomaterials, such as Matrigel, decellularized extracellular matrices, chitosan, silk fibroin hydrogels, and human amniotic membrane are evaluated for their biocompatibility and ability to support lacrimal gland cells. Synthetic biomaterials, like polyethersulfone, polyesters, and biodegradable polymers (PLLA and PLGA), are assessed for their mechanical properties and potential to create scaffolds that replicate the complex architecture of the LG. We also explore the integration of growth factors and stem cells with these biomaterials to enhance tissue regeneration. Challenges such as achieving proper vascularization, innervation, and long-term functionality of engineered tissues are discussed. Advances in 3D bioprinting and scaffold fabrication techniques are highlighted as promising avenues to overcome current limitations. Full article
(This article belongs to the Section Biomaterials)
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21 pages, 13768 KB  
Article
Cyclic Fatigue Failure of Perforated 3D-Printed Polylactide (PLA) Specimens by Inserted Pin Loading
by J. S. Hertel, Y. W. Kwon and D. Sachau
Materials 2024, 17(22), 5394; https://doi.org/10.3390/ma17225394 - 5 Nov 2024
Viewed by 1369
Abstract
The failure of 3D-printed Polylactide (PLA) specimens with circular holes was studied under tensile and cyclic loading, respectively, by an inserted pin. Experiments were conducted for the perforated PLA specimens with various print angles from 0° to 90°, as well as [0°/90°]s and [...] Read more.
The failure of 3D-printed Polylactide (PLA) specimens with circular holes was studied under tensile and cyclic loading, respectively, by an inserted pin. Experiments were conducted for the perforated PLA specimens with various print angles from 0° to 90°, as well as [0°/90°]s and [0°/±45°/90°]s. The hole locations varied along the specimens. The PLA specimens showed two different failure modes: one through the print lines and the other between the print lines. Different print angles resulted in different tensile failure stresses under pin loading. The cyclic tests of different print angles showed very similar S-N data as the applied stresses were normalized to their tensile failure stresses if the failure mode was through the print lines. On the other hand, cyclic failure between print lines showed distinctly separated S-N data, even with the normalized applied stresses. The tensile failure stresses, failure locations, and orientations were successfully predicted using the failure criterion that is based on both stress and stress gradient conditions. A proposed mathematical interpolation equation provided good estimations of the tensile failure stresses and S-N curves of specimens with different print angles once the failure stresses were known for the 0° to 90° specimens. Full article
(This article belongs to the Special Issue Numerical Modeling and Dynamic Analysis of Composite Materials)
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21 pages, 41643 KB  
Article
Mechanical Characterization of Sustainable Mortars with Recycled Aggregates from Construction and Demolition Wastes: An Experimental Investigation
by Luca Soldati, Michele Bacciocchi and Angelo Marcello Tarantino
Materials 2024, 17(22), 5409; https://doi.org/10.3390/ma17225409 - 5 Nov 2024
Cited by 2 | Viewed by 1386
Abstract
The use of recycled aggregates in the production of concrete and mortar represents a sustainable way to reintroduce these constituents—which are typically treated as waste and disposed of—in the production chain, providing new value to potentially polluting materials. The effect of recycled aggregates [...] Read more.
The use of recycled aggregates in the production of concrete and mortar represents a sustainable way to reintroduce these constituents—which are typically treated as waste and disposed of—in the production chain, providing new value to potentially polluting materials. The effect of recycled aggregates has been widely studied in the production of concrete due to the directions of National Standards in Italy; however, their role in the manufacturing of mortar must be investigated further due to the high variability that can be observed in the literature. In particular, the aim of this paper is the mechanical characterization of sustainable mortars defined by different mix designs and different binders, in which the aggregates are gradually replaced by a recycled sand obtained from the grinding of construction and demolition wastes, which could include old concrete, clay bricks, and minimal amounts of other kinds of residual materials. This investigation is carried out through experimentation, taking into account four different mortar compositions defined by an increasing percentage of recycled constituents. Virgin aggregates are also studied for the sake of comparison. The results, accomplished through a three-point bending test and an unconfined compression test, show that it is still possible to maintain acceptable mechanical properties by using these wastes as aggregates in spite of a decrease in the analyzed values. In general, the mean reductions with respect to the use of natural aggregates are about 30–40% and 35–55%, respectively, for compressive and flexural strengths. It should be highlighted that some experimental sets provide a maximum reduction of 70–80%, but the results are still within the limitations of the standards. This aspect can be considered to be a good compromise since the production of this sustainable construction material can represent a solution that is able to reduce the extreme exploitation of natural resources, the pressure on landfills, and the consumption of energy, which are related to the construction industry. Full article
(This article belongs to the Special Issue Advanced and Sustainable Low-Carbon Cement and Concrete Materials (Second Edition))
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24 pages, 11388 KB  
Article
Enhancement of 5-Fluorouracil Drug Delivery in a Graphene Oxide Containing Electrospun Chitosan/Polyvinylpyrrolidone Construct
by Jamie J. Grant, Suresh C. Pillai, Tatiana S. Perova, Barry Brennan, Steven J. Hinder, Marion McAfee, Sarah Hehir and Ailish Breen
Materials 2024, 17(21), 5300; https://doi.org/10.3390/ma17215300 - 31 Oct 2024
Viewed by 1529
Abstract
Electrospun nanofibrous mats, consisting of chitosan (CS) and polyvinylpyrrolidone (PVP), were constructed with the addition of graphene oxide (GO) for enhancement of delivery of the 5-Fluorouracil (5-Fu) chemotherapy drug. Upon studying the range of GO concentrations in CS/PVP, the concentration of 0.2% w [...] Read more.
Electrospun nanofibrous mats, consisting of chitosan (CS) and polyvinylpyrrolidone (PVP), were constructed with the addition of graphene oxide (GO) for enhancement of delivery of the 5-Fluorouracil (5-Fu) chemotherapy drug. Upon studying the range of GO concentrations in CS/PVP, the concentration of 0.2% w/v GO was chosen for inclusion in the drug delivery model. SEM showed bead-free, homogenous fibres within this construct. This construct also proved to be non-toxic to CaCo-2 cells over 24 and 48 h exposure. The construction of a drug delivery vehicle whereby 5-Fu was loaded with and without GO in various concentrations showed several interesting findings. The presence of CS/PVP was revealed through XPS, FTIR and Raman spectroscopies. FTIR was also imperative for the analysis of 5-Fu while Raman exclusively highlighted the presence of GO in the samples. In particular, a detailed analysis of the IR spectra recorded using two FTIR spectrometers, several options for determining the concentration of 5-Fu in composite fibre systems CS/PVP/5-Fu and GO/CS/PVP/5-Fu were demonstrated. By analysis of Raman spectra in the region of D and G bands, a linear dependence of ratios of integrated intensities of AD and AG on the intensity of host polymer band at 1425 cm−1 vs. GO content was found. Both methods, therefore, can be used for monitoring of GO content and 5-Fu release in studied complex systems. After incorporating the chemotherapy drug 5-Fu into the constructs, cell viability studies were also performed. This study demonstrated that GO/CS/PVP/5-Fu constructs have potential in chemotherapy drug delivery systems. Full article
(This article belongs to the Special Issue Synthesis, Physicochemical Properties, and Applications of Low-Dimensional Materials)
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14 pages, 9541 KB  
Article
Magnetic Memory Effects in BaFe2(As0.68P0.32)2 Superconducting Single Crystal
by Alina M. Badea (Ionescu), Ion Ivan, Corneliu F. Miclea, Daniel N. Crisan, Armando Galluzzi, Massimiliano Polichetti and Adrian Crisan
Materials 2024, 17(21), 5340; https://doi.org/10.3390/ma17215340 - 31 Oct 2024
Cited by 1 | Viewed by 951
Abstract
Among many iron-based superconductors, isovalently substituted BaFe2(As1−xPx)2 displays, for x ≈ 0.3, apart from the quite usual Second Magnetization Peak (SMP) in the field dependence of the critical current density, an unusual peak effect in the [...] Read more.
Among many iron-based superconductors, isovalently substituted BaFe2(As1−xPx)2 displays, for x ≈ 0.3, apart from the quite usual Second Magnetization Peak (SMP) in the field dependence of the critical current density, an unusual peak effect in the temperature dependence of the critical current density in the constant field, which is related to the rhombic-to-square (RST) structural transition of the Bragg vortex glass (BVG). By using multi-harmonic AC susceptibility investigations in three different cooling regimes—field cooling, zero-field cooling, and field cooling with measurements during warming up—we have discovered the existence of a temperature region in which there is a pronounced magnetic memory effect, which we attributed to the direction of the structural transition. The observed huge differences in the third harmonic susceptibility at low and high AC frequencies indicates the difference in the time-scale of the structural transition in comparison with the timescale of the vortex excitations. Our findings show that the RST influence on the vortex dynamics goes beyond the previously observed influence on the onset of the SMP. Full article
(This article belongs to the Special Issue Advances in Cuprates and Iron-Based Superconductors: Physics, Properties, and Applications)
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19 pages, 1977 KB  
Article
Measuring the Electro-Optical Kerr Effect Against the Background of Electro-Absorption Modulation in Liquids
by Rafał Ledzion, Marek Izdebski and Anita Rambo
Materials 2024, 17(21), 5346; https://doi.org/10.3390/ma17215346 - 31 Oct 2024
Cited by 1 | Viewed by 1200
Abstract
A new approach to the dynamic polarimetric method is proposed, which allows for the decoupling of electro-optical Kerr effect measurements from the electro-absorption effect in partially transparent liquids. The method is illustrated by using the results of engine oil measurements as a function [...] Read more.
A new approach to the dynamic polarimetric method is proposed, which allows for the decoupling of electro-optical Kerr effect measurements from the electro-absorption effect in partially transparent liquids. The method is illustrated by using the results of engine oil measurements as a function of temperature and modulating field frequency. It was shown that the birefringence induced in the sample, the modulation of the ordinary wave transmission, and the modulation of the extraordinary wave transmission in the sample can be shifted in phase with respect to the square of the applied alternating modulating field. Each of these three phase shifts can depend differently on the temperature and frequency. Neglecting the influence of electro-absorption on electro-optical measurements in liquids or considering electro-absorption as an effect correlated in phase with induced birefringence may lead to significant measurement errors. This indicates that the Kerr constant and the electro-absorption coefficients for an alternating electric field should be considered as complex quantities instead of real values, as they have been traditionally. The proposed approach fills an important gap in measurement techniques described in the literature, which may provide erroneous results for measurements of the Kerr constant in partially transparent liquids including many industrially important liquids. Full article
(This article belongs to the Section Optical and Photonic Materials)
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11 pages, 4971 KB  
Article
Iron-Based Superconductors for High-Field Applications: Realization of High Engineering Critical Current Density
by Peng Yang, He Huang, Meng Han, Cong Liu, Chao Yao, Yanwei Ma and Dongliang Wang
Materials 2024, 17(21), 5306; https://doi.org/10.3390/ma17215306 - 31 Oct 2024
Cited by 1 | Viewed by 1528
Abstract
Iron-based superconductors have strong potential for magnet applications through their very high upper critical field, low anisotropy and manufacturability through the powder-in-tube (PIT) route. The engineering critical current density (Je) is a key parameter for measuring the maximum current density [...] Read more.
Iron-based superconductors have strong potential for magnet applications through their very high upper critical field, low anisotropy and manufacturability through the powder-in-tube (PIT) route. The engineering critical current density (Je) is a key parameter for measuring the maximum current density that superconducting materials can withstand in practical applications. It serves as a bridge between theoretical research and practical applications of superconductors and has great significance in promoting the development and application of superconducting technology. In this study, Ag sheathed Ba0.6K0.4Fe2As2 (Ba-122) iron-based superconducting tapes were prepared by using the process of drawing, flat rolling and heat treatment by hot pressing (HP). For the first time, the filling factor of the tapes increased to about 40%, leading to a reduction in the volume fraction of Ag, consequently lowering the overall cost. The optimal parameters for achieving high transport Je were obtained by comparing the effects of different HP pressures on the properties and micro-morphology of the tapes. The prepared mono-filament tapes are capable of carrying the transport Je of 4.1 × 104 A/cm2 (Ic = 350 A) at 4.2 K, 10 T, marking the highest Je reported for Ba-122 wires and tapes to date. Our results show that high transport Je can be obtained in Ba-122 superconducting tapes, and iron-based superconductors have a promising future in practical applications. Full article
(This article belongs to the Special Issue Advances in Cuprates and Iron-Based Superconductors: Physics, Properties, and Applications)
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18 pages, 3418 KB  
Article
On the Influence of Welding Parameters and Their Interdependence During Robotic Continuous Ultrasonic Welding of Carbon Fibre Reinforced Thermoplastics
by Filipp Köhler, Irene Fernandez Villegas, Clemens Dransfeld and Axel Herrmann
Materials 2024, 17(21), 5282; https://doi.org/10.3390/ma17215282 - 30 Oct 2024
Cited by 3 | Viewed by 1541
Abstract
Ultrasonic welding of fibre-reinforced thermoplastics is a joining technology with high potential for short welding times and low energy consumption. While the majority of the current studies on continuous ultrasonic welding have so far focused on woven reinforcements, unidirectional materials are preferred for [...] Read more.
Ultrasonic welding of fibre-reinforced thermoplastics is a joining technology with high potential for short welding times and low energy consumption. While the majority of the current studies on continuous ultrasonic welding have so far focused on woven reinforcements, unidirectional materials are preferred for highly loaded aerospace components due to their better mechanical performance. Therefore, this paper investigates the influence and interdependence of the welding speed, amplitude, and energy director thickness on the weld quality of adherends made of unidirectional composites. The quality of the welded joints is assessed by a single-lap shear strength and fracture surface analysis complemented by the microscopic analysis of cross-sections and comparison to a co-consolidated reference. The results showed that the welding process is highly affected by changing welding speeds for a given amplitude. Furthermore, while lower amplitudes lead to significant scatter in the welding quality, higher amplitudes result in increased heating rates and a fully molten energy director even for high welding speeds. Nevertheless, insufficient consolidation at high welding speeds results in porosity in the weld line. Finally, it was observed that thicker, and therefore more compliant, energy directors lead to more uniform melting of the energy director and less deviation in the weld quality for a wider range of welding speeds. Full article
(This article belongs to the Special Issue Ultrasound for Material Characterization and Processing (3rd Edition))
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11 pages, 9506 KB  
Article
Multiscale Analysis of Surface Topography for Engineering Applications in the Casting Industry
by Damian Gogolewski, Tomasz Kozior and Paweł Zmarzły
Materials 2024, 17(21), 5272; https://doi.org/10.3390/ma17215272 - 30 Oct 2024
Cited by 1 | Viewed by 886
Abstract
This paper presents the results of studies aimed at assessing the impact of the molding process on the variability of surface irregularities of casting models. This research was conducted using a selected multiscale method, i.e., wavelet transformation, in both discrete and continuous perspective. [...] Read more.
This paper presents the results of studies aimed at assessing the impact of the molding process on the variability of surface irregularities of casting models. This research was conducted using a selected multiscale method, i.e., wavelet transformation, in both discrete and continuous perspective. The test samples were made both based on traditional methods of manufacturing casting models, i.e., machining of aluminum and wood, as well as using three additive technologies. The impact of the forming process on the variability of the topography of the produced models was evaluated. This research comprehensively relates to the assessment of the applicability of additive technologies, which are increasingly used in various industrial areas, as well as the impact of the process on surface topography in relation to scale. The statistical assessment based on the ANOVA analysis demonstrated that it is possible to distinguish between the surfaces before and after a specific number of forming cycles. Studies have shown that the impact of the forming process is relatively small, mainly affecting the long-term irregularity components, and there are no functional dependencies in terms of the impact of the forming process on the variation in surface topography in relation to the manufacturing method or its parameters. Full article
(This article belongs to the Special Issue Recent Trends in Roughness Measurement and Data Analysis of Machined Surfaces (2nd Edition))
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12 pages, 4520 KB  
Article
Magnetic CuFe2O4 Spinel–Polypyrrole Pseudocapacitive Composites for Energy Storage
by Mahmoud Awad and Igor Zhitomirsky
Materials 2024, 17(21), 5249; https://doi.org/10.3390/ma17215249 - 28 Oct 2024
Cited by 1 | Viewed by 1363
Abstract
This investigation focused on the fabrication of ceramic ferrimagnetic CuFe2O4–conductive polypyrrole (PPy) composites for energy storage. CuFe2O4 with a crystal size of 20–30 nm and saturation magnetization of 31.4 emu g−1 was prepared by hydrothermal [...] Read more.
This investigation focused on the fabrication of ceramic ferrimagnetic CuFe2O4–conductive polypyrrole (PPy) composites for energy storage. CuFe2O4 with a crystal size of 20–30 nm and saturation magnetization of 31.4 emu g−1 was prepared by hydrothermal synthesis, and PPy was prepared by chemical polymerization. High-active-mass composite electrodes were fabricated for energy storage in supercapacitors for operation in a sodium sulfate electrolyte. The addition of PPy to CuFe2O4 resulted in a decrease in charge transfer resistance and an increase in capacitance in the range from 1.20 F cm−2 (31 F g−1) to 4.52 F cm−2 (117.4 F g−1) at a 1 mV s−1 sweep rate and from 1.17 F cm−2 (29.9 F g−1) to 4.60 F cm−2 (120.1 F g−1) at a 3 mA cm−2 current density. The composites showed higher capacitance than other magnetic ceramic composites of the same mass containing PPy in the same potential range and exhibited improved cyclic stability. The magnetic behavior of the composites was influenced by the magnetic properties of ferrimagnetic CuFe2O4 and paramagnetic PPy. The composites showed a valuable combination of capacitive and magnetic properties and enriched materials science of magnetic supercapacitors for novel applications based on magnetoelectric and magnetocapacitive properties. Full article
(This article belongs to the Special Issue Processing, Characterization and Applications of Ceramic Matrix Composites)
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16 pages, 5871 KB  
Article
Effect of Natural Inhibitors on the Corrosion Properties of Grade 2 Titanium Alloy
by Mehrdad Faraji, Luca Pezzato, Arshad Yazdanpanah, Giacomo Nardi, Mojtaba Esmailzadeh and Irene Calliari
Materials 2024, 17(21), 5202; https://doi.org/10.3390/ma17215202 - 25 Oct 2024
Cited by 4 | Viewed by 1484
Abstract
This study investigates the effects of natural inhibitors (pomegranate, algae, and tomato extracts) on the corrosion resistance of titanium (grade 2). To deepen understanding the inhibition mechanism, Molecular Dynamic (MD) and Monte Carlo (MC) simulations were employed to analyze adsorption behaviors and identify [...] Read more.
This study investigates the effects of natural inhibitors (pomegranate, algae, and tomato extracts) on the corrosion resistance of titanium (grade 2). To deepen understanding the inhibition mechanism, Molecular Dynamic (MD) and Monte Carlo (MC) simulations were employed to analyze adsorption behaviors and identify optimal adsorption sites on titanium oxide (TiO2) surfaces for compounds within the inhibitors. Results indicate non-flat adsorption orientations, with pomegranate peel extract components showing superior inhibition capabilities, attributed to the formation of strong O-H chemical bonds with the TiO2 surface. In the experimental part of the study Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) were conducted. Two electrolytes were tested: a solution 3.5% NaCl and a solution 0.5 M NaOH. All the tests were performed with 5% of inhibitor and with the reference solution. Also, inhibition efficiency was calculated on the base of PDP tests. The study found that pomegranate extract can act as a good corrosion inhibitor for titanium alloy in aqueous solutions 0.5 M NaOH. This was demonstrated by the increase in the corrosion potential and impedance modulus and decrease in the corrosion current density after the addition of pomegranate extract to the solution. However, in a 3.5% NaCl solution, the efficacy of pomegranate extract was less pronounced, probably due to the high aggressivity of the electrolyte. Tomato and algae extract have instead shown very low inhibition effects in all the tested conditions. Full article
(This article belongs to the Special Issue Corrosion Behavior and Mechanical Properties of Metallic Materials)
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15 pages, 4658 KB  
Article
The Impact of the Final Sintering Temperature on the Microstructure and Dielectric Properties of Ba0.75Ca0.25TiO3 Perovskite Ceramics
by Kamil Feliksik, Małgorzata Adamczyk-Habrajska, Jolanta Makowska, Joanna A. Bartkowska, Tomasz Pikula, Rafał Panek and Oliwia Starczewska
Materials 2024, 17(21), 5210; https://doi.org/10.3390/ma17215210 - 25 Oct 2024
Cited by 1 | Viewed by 1141
Abstract
Ba0.75Ca0.25TiO3 ceramics were successfully synthesized by a simple solid-state reaction method. This study examined the influence of sintering temperature on the structure, microstructure, dielectric properties and electrical behavior of the material. The XRD analysis reveals that the tetragonal [...] Read more.
Ba0.75Ca0.25TiO3 ceramics were successfully synthesized by a simple solid-state reaction method. This study examined the influence of sintering temperature on the structure, microstructure, dielectric properties and electrical behavior of the material. The XRD analysis reveals that the tetragonal phase (P4mm) is dominant in all the synthesized materials, with those sintered at T = 1400 °C and T = 1450 °C being single-phase, while others exhibit a minor orthorhombic phase (Pbnm). Higher sintering temperatures promoted better grain boundary formation and larger grain sizes. The electric permittivity increased with temperature up to T = 1400 °C, followed by a sharp decline at T = 1450 °C. Additionally, the Curie temperature decreased with increasing sintering temperature, indicating changes in phase transition characteristics. Thermal analysis showed that higher sintering temperatures led to sharper heat capacity peaks, while pyroelectric and thermally stimulated depolarization currents were maximized at T = 1400 °C due to oxygen vacancies. These findings highlight the significant impact of sintering temperature on the material’s structural and functional properties. Full article
(This article belongs to the Special Issue Synergy in Polyphase Materials: Harnessing the Power of Glass and Ceramics)
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