Materials

17 pages, 3346 KiB

Open AccessEditor’s ChoiceArticle

The Use of 3D Printing Filaments to Build Moisture Sensors in Porous Materials

by Magdalena Paśnikowska-Łukaszuk, Joanna Szulżyk-Cieplak, Magda Wlazło, Jarosław Zubrzycki, Ewa Łazuka, Arkadiusz Urzędowski and Zbigniew Suchorab

Materials 2025, 18(1), 115; https://doi.org/10.3390/ma18010115 - 30 Dec 2024

Viewed by 461

Abstract

This study explores the application of materials used in 3D printing to manufacture the housings of non-invasive sensors employed in measurements using a TDR (Time Domain Reflectometry) meter. The research investigates whether sensors designed with 3D printing technology can serve as viable alternatives [...] Read more.

This study explores the application of materials used in 3D printing to manufacture the housings of non-invasive sensors employed in measurements using a TDR (Time Domain Reflectometry) meter. The research investigates whether sensors designed with 3D printing technology can serve as viable alternatives to conventional invasive and non-invasive sensors. This study focuses on innovative approaches to designing humidity sensors, utilizing Fused Deposition Modeling (FDM) technology to create housings for non-invasive sensors compatible with TDR devices. The paper discusses the use of 3D modeling technology in sensor design, with particular emphasis on materials used in 3D printing, notably polylactic acid (PLA). Environmental factors, such as moisture in building materials, are characterized, and the need for dedicated sensor designs is highlighted. The software utilized in the 3D modeling and printing processes is also described. The Materials and Methods Section provides a detailed account of the construction process for the non-invasive sensor housing and the preparation for moisture measurement in silicate materials using the designed sensor. A prototype sensor was successfully fabricated through 3D printing. Using the designed sensor, measurements were conducted on silicate samples soaked in aqueous solutions with water absorption levels ranging from 0% to 10%. Experimental validation involved testing silicate samples with the prototype sensor to evaluate its effectiveness. The electrical permittivity of the material was calculated, and the root-mean-square error (RMSE) was determined using classical computational methods and machine learning techniques. The RMSE obtained using the classical method was 0.70. The results obtained were further analyzed using machine learning models, including Gaussian Process Regression (GPR) and Support Vector Machine (SVM). The GPR model achieved an RMSE of 0.15, while the SVM model yielded an RMSE of 0.25. These findings confirm the sensor’s effectiveness and its potential for further research and practical applications. Full article

(This article belongs to the Special Issue 3D-Printed Composite Structures: Design, Properties and Application)

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26 pages, 14474 KiB

Open AccessEditor’s ChoiceArticle

Development of a Stable Process for Wire Embedding in Fused Filament Fabrication Printing Using a Geometric Correction Model

by Valentin Wilhelm Mauersberger, Fabian Ziervogel, Linda Weisheit, Lukas Boxberger and Welf-Guntram Drossel

Materials 2025, 18(1), 41; https://doi.org/10.3390/ma18010041 - 26 Dec 2024

Viewed by 345

Abstract

Using a newly developed tool head with an additional rotational axis and a wire feed, wires can be directly processed in the fused filament fabrication (FFF) process. Thus, electrical structures such as conductive paths, coils, heating elements, or sensors can be integrated into [...] Read more.

Using a newly developed tool head with an additional rotational axis and a wire feed, wires can be directly processed in the fused filament fabrication (FFF) process. Thus, electrical structures such as conductive paths, coils, heating elements, or sensors can be integrated into polymer parts. However, the accuracy of the wire deposition in curved sections of the print track is insufficient. To improve the wire position, a geometric correction model was set up, converted into G-code, and validated using test prints for different wire parameters. For this, a sample of printed arcs was evaluated regarding wire position and embedding quality using various visual methods. This also determined the optimal cooling time for the model. The process parameters extrusion coefficient and feed were then varied to identify optimal process parameters for a stable and at the same time efficient process. By varying the wire (copper, constantan) and polymer material (PLA, PETG), the model was checked for general validity. It was found that the position of the ø 0.2 mm wire can be improved with the correction model. Different sets of parameters can be found that enable good quality of embedding and wire position. Full article

(This article belongs to the Special Issue Current and Future Trends in Additive Manufacturing)

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15 pages, 11668 KiB

Open AccessEditor’s ChoiceArticle

Analysis of the Properties of Anticorrosion Systems Used for Structural Component Protection in Truck Trailers

by Wojciech Skotnicki and Dariusz Jędrzejczyk

Materials 2024, 17(24), 6303; https://doi.org/10.3390/ma17246303 - 23 Dec 2024

Viewed by 493

Abstract

The article compares the properties of coatings (cataphoretic, hot-dip zinc, and thermo-diffusion zinc) applied to steel components used in the automotive industry. The research focused on the analysis of corrosion resistance, hardness measurements, and tribological properties conducted on steel guides used in trailer [...] Read more.

The article compares the properties of coatings (cataphoretic, hot-dip zinc, and thermo-diffusion zinc) applied to steel components used in the automotive industry. The research focused on the analysis of corrosion resistance, hardness measurements, and tribological properties conducted on steel guides used in trailer and truck body structures as well as fasteners (M12 × 40 bolts). The base surfaces were cleaned chemically. Corrosion resistance was tested in a salt chamber, while coating thickness was measured using the magnetic induction method. Coating hardness (HV 0.02) was assessed with a microhardness tester, and tribological properties were tested under dry friction conditions. The results showed that the zinc coatings demonstrated corrosion resistance far superior to paint coatings. Full article

(This article belongs to the Special Issue Metal Coatings for Wear and Corrosion Applications (Second Edition))

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19 pages, 8834 KiB

Open AccessEditor’s ChoiceArticle

Protective Properties of Silane Composite Coatings Modified with Poly(3,4-ethylenedioxythiophene) with Heteropolyacid on X20Cr13 and 41Cr4 Steel

by Aleksandra Kucharczyk-Kotlewska, Lidia Adamczyk, Krzysztof Miecznikowski and Agata Dudek

Materials 2024, 17(24), 6177; https://doi.org/10.3390/ma17246177 - 18 Dec 2024

Viewed by 396

Abstract

This paper describes the methodology of the preparation and analyses of the structure and anticorrosion properties of silane coatings modified with poly(3,4-ethylenedioxythiophene) (PEDOT) with phosphododecamolybdic acid (PMo₁₂). Protective coatings, consisting of vinyltrimethoxysilane (VTMS), PEDOT powder with PMo₁₂ admixture (at different [...] Read more.

This paper describes the methodology of the preparation and analyses of the structure and anticorrosion properties of silane coatings modified with poly(3,4-ethylenedioxythiophene) (PEDOT) with phosphododecamolybdic acid (PMo₁₂). Protective coatings, consisting of vinyltrimethoxysilane (VTMS), PEDOT powder with PMo₁₂ admixture (at different concentrations), and ethanol, were deposited on X20Cr13 and 41Cr4 steels by immersion. The physicochemical properties of these silane coatings (e.g., surface morphology, thickness, roughness, and adhesion to the substrate) were elucidated using a digital microscope, a Fourier transform infrared spectrophotometer with attenuated total reflectance, and various electrochemical diagnostic techniques. Protective properties were assessed in acidified sulfate solutions with and without chloride ions (pH 2). Experimental results have shown that this coating displayed the effective protection of steel against general and pitting corrosion, stabilized the corrosion potential in the passive state, and provided barrier protection. Full article

(This article belongs to the Special Issue Fabrication and Properties of Functional Coatings Under Extreme Conditions)

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14 pages, 2706 KiB

Open AccessEditor’s ChoiceArticle

Evolution of Chemical, Structural, and Mechanical Properties of Titanium Nitride Films with Different Thicknesses Fabricated Using Pulsed DC Magnetron Sputtering

by Wei Mao, Runze Qi, Jiali Wu, Zhe Zhang and Zhanshan Wang

Materials 2024, 17(24), 6067; https://doi.org/10.3390/ma17246067 - 12 Dec 2024

Viewed by 474

Abstract

Considering the application of titanium nitride (TiN) films as a release layer in producing Wolter-I X-ray telescope mirror shells by the electroformed nickel replication (ENR) technique, this research pays attention to the influence of nanometer-scale thickness variation in the microstructure and physical properties [...] Read more.

Considering the application of titanium nitride (TiN) films as a release layer in producing Wolter-I X-ray telescope mirror shells by the electroformed nickel replication (ENR) technique, this research pays attention to the influence of nanometer-scale thickness variation in the microstructure and physical properties of TiN films deposited by the pulsed direct current (DC) magnetron sputtering method. This topic has received limited attention in the existing literature. TiN films (9.8 nm to 42.9 nm) were fabricated to comprehensively analyze the evolution in microstructure, depth distribution of elements, surface morphology, and intrinsic stress. With increasing thickness, TiN transitioned from amorphous to (200) and (111)–(200) mixed-oriented crystallization, explaining inflection points in the increasing roughness curve. Elements (C, N, O, Si, and Ti) and chemical bond proportions (Ti-N, Ti-N-O, and Ti-O) varied with film depth, and the fitting of film density can be optimized according to these variations. Crystallite size increased with thickness, which led to a reduction in intrinsic stress. It is evident that as film thickness increases, TiN forms a stable crystal structure, thereby reducing intrinsic stress, but resulting in increased roughness. Considering the impact of changes in thin film thickness on physical properties such as roughness, crystallinity, and intrinsic stress, a TiN film with a thickness of approximately 25 nm is deemed suitable for application as a release layer. Full article

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

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34 pages, 1503 KiB

Open AccessEditor’s ChoiceArticle

The Generalized Phase Rule, the Extended Definition of the Degree of Freedom, the Component Rule and the Seven Independent Non-Compositional State Variables: To the 150th Anniversary of the Phase Rule of Gibbs

by George Kaptay

Materials 2024, 17(24), 6048; https://doi.org/10.3390/ma17246048 - 10 Dec 2024

Viewed by 933

Abstract

The phase rule of Gibbs is one of the basic equations in phase equilibria. Although it has been with us for 150 years, discussions, interpretations and extensions have been published. Here, the following new content is provided: (i). the choice of independent components [...] Read more.

The phase rule of Gibbs is one of the basic equations in phase equilibria. Although it has been with us for 150 years, discussions, interpretations and extensions have been published. Here, the following new content is provided: (i). the choice of independent components is discussed, and the component rule is introduced, (ii). independent state variables are divided into compositional and non-compositional ones, (iii). the generalized phase rule is derived replacing number two in the original phase rule by the number of independent non-compositional state variables introduced above, (iv). the degree of freedom is decreased by the number of compositional constraints in special points (azeotrope and congruent melting) of phase diagrams, (v). a rule is derived connecting the maximum number of coexisting phases with the dimensions of the phase diagram, (vi). examples show how to apply the phase rule to unary, binary and ternary phase diagrams and their sections, (vii). the same is extended with the discussion of calculable and not calculable phase fractions, (viii). it is shown that the current definition of the degree of freedom is not sufficient in the number of cases, (ix). the current definition of the degree of freedom is extended, (x). the application of the generalized phase rule is demonstrated when other non-compositional state variables are applied for nano-phase diagrams, and/or for phase diagrams under the influence of electric potential difference, external magnetic field, mechanical strain or the gravitational field. Full article

(This article belongs to the Section Materials Chemistry)

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30 pages, 7774 KiB

Open AccessEditor’s ChoiceReview

Perovskite in Triboelectric Nanogenerator and the Hybrid Energy Collection System

by Tong Wu, Zequan Zhao, Yin Lu, Hanzhang Yang, Xiaoning Liu, Xia Cao and Ning Wang

Materials 2024, 17(23), 6019; https://doi.org/10.3390/ma17236019 - 9 Dec 2024

Viewed by 727

Abstract

In the context of escalating energy demands and environmental sustainability, the paradigm of global energy systems is undergoing a transformative shift to innovative and reliable energy-harvesting techniques ranging from solar cells to triboelectric nanogenerators (TENGs) to hybrid energy systems, where a fever in [...] Read more.

In the context of escalating energy demands and environmental sustainability, the paradigm of global energy systems is undergoing a transformative shift to innovative and reliable energy-harvesting techniques ranging from solar cells to triboelectric nanogenerators (TENGs) to hybrid energy systems, where a fever in the study of perovskite materials has been set off due to the excellent optoelectronic properties and defect tolerance features. This review begins with the basic properties of perovskite materials and the fundamentals of TENGs, including their working principles and general developing strategy, then delves into the key role of perovskite materials in promoting TENG-based hybrid technologies in terms of energy conversion. While spotlighting the coupling of triboelectric–optoelectronic effects in harnessing energy from a variety of sources, thereby transcending the limitations inherent to single-source energy systems, this review pays special attention to the strategic incorporation of perovskite materials into TENGs and TENG-based energy converting systems, which heralds a new frontier in enhancing efficiency, stability, and adaptability. At the end, this review highlights the remaining challenges such as stability, efficiency, and functionality for applications in TENG-based energy-harvesting systems, aiming to provide a comprehensive overview of the current landscape and the prospective trajectory of the role of perovskite materials in TENG-based energy-harvesting technologies within the renewable energy sector. Full article

(This article belongs to the Special Issue Featured Papers and Reviews of Advanced Materials for Sensing, Energy Conversion and Storage)

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18 pages, 9431 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Wear Resistance and Thermal Dissipation of Copper–Graphene Composite Coatings via Pulsed Electrodeposition for Circuit Breaker Applications

by Daniele Almonti, Daniel Salvi, Nadia Ucciardello and Silvia Vesco

Materials 2024, 17(23), 6017; https://doi.org/10.3390/ma17236017 - 9 Dec 2024

Viewed by 692

Abstract

Copper, though highly conductive, requires improved wear resistance and thermal dissipation in applications that involve continuous movement and current-induced vibrations, such as power breakers. Conventional solutions, such as copper–tungsten alloys or lubricant use, face limitations in durability, friction, or environmental impact. This study [...] Read more.

Copper, though highly conductive, requires improved wear resistance and thermal dissipation in applications that involve continuous movement and current-induced vibrations, such as power breakers. Conventional solutions, such as copper–tungsten alloys or lubricant use, face limitations in durability, friction, or environmental impact. This study explores the development of copper–graphene (Cu-GNPs) composite coatings using pulsed electrodeposition to enhance the tribological, thermal, and mechanical properties of circuit breaker components by adopting an industrially scalable technique. The influence of deposition bath temperature, duty cycle, and frequency on coating morphology, hardness, wear resistance, and heat dissipation was systematically evaluated using a 2³ full factorial design and an Analysis of Variance (ANOVA). The results revealed that optimized pulsed electrodeposition significantly improved coating performance: hardness increased by 76%, wear volume decreased by more than 99%, and friction coefficient stabilized at 0.2, reflecting effective graphene integration. The addition of graphene further improved thermal diffusivity by 19.5%, supporting superior heat dissipation. These findings suggest that pulsed copper–graphene composite coatings offer a promising alternative to traditional copper alloys, enhancing the lifespan and reliability of electronic components through improved wear resistance, lower friction, and superior heat transfer. Full article

(This article belongs to the Special Issue Advanced Coating Research for Metal Surface Protection)

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15 pages, 7639 KiB

Open AccessEditor’s ChoiceArticle

Superhydrophobic Surfaces as a Potential Skin Coating to Prevent Jellyfish Stings: Inhibition and Anti-Tentacle Adhesion in Nematocysts of Jellyfish Nemopilema nomurai

by Yichen Xie, Yuanyuan Sun, Rongfeng Li, Song Liu, Ronge Xing, Pengcheng Li and Huahua Yu

Materials 2024, 17(23), 5983; https://doi.org/10.3390/ma17235983 - 6 Dec 2024

Viewed by 620

Abstract

The development of skin-protective materials that prevent the adhesion of cnidarian nematocysts and enhance the mechanical strength of these materials is crucial for addressing the issue of jellyfish stings. This study aimed to construct superhydrophobic nanomaterials capable of creating a surface that inhibits [...] Read more.

The development of skin-protective materials that prevent the adhesion of cnidarian nematocysts and enhance the mechanical strength of these materials is crucial for addressing the issue of jellyfish stings. This study aimed to construct superhydrophobic nanomaterials capable of creating a surface that inhibits nematocyst adhesion, therefore preventing jellyfish stings. We investigated wettability and nematocyst adhesion on four different surfaces: gelatin, polydimethylsiloxane (PDMS), dodecyl trichlorosilane (DTS)-modified SiO₂, and perfluorooctane triethoxysilane (PFOTS)-modified TiO₂. Our findings revealed that an increase in hydrophobicity significantly inhibited nematocyst adhesion. Furthermore, DTS-modified sprayed SiO₂ and PFOTS-modified sprated TiO₂ were further enhanced with low-surface-energy substances—cellulose nanofibers (CNF) and chitin nanocrystals (ChNCs)—to improve both hydrophobicity and mechanical strength. After incorporating CNF and ChNCs, the surface of s-TiO₂-ChNCs exhibited a contact angle of 153.49° even after undergoing abrasion and impact tests, and it maintained its hydrophobic properties with a contact angle of 115.21°. These results indicate that s-TiO₂-ChNCs can serve as an effective skin coating to resist tentacle friction. In conclusion, this study underscores the importance of utilizing hydrophobic skin materials to inhibit the adhesion of tentacle nematocysts, providing a novel perspective for protection against jellyfish stings. Full article

(This article belongs to the Special Issue Superhydrophobic Coating Materials: Preparation, Strategy and Application)

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9 pages, 4243 KiB

Open AccessEditor’s ChoiceArticle

Phase Evolution in Mn_1.6Zn_0.2Ni_0.6Mg_0.2Al_0.4O₄ High-Entropy Oxide Films by Heat Treatment

by Wei Ren, Xianhai Liu, Wenting Wu and Weili Wang

Materials 2024, 17(23), 5967; https://doi.org/10.3390/ma17235967 - 5 Dec 2024

Viewed by 473

Abstract

In this work, Mn-Zn-Ni-Mg-Al multi-layer films were annealed in air at different temperatures to form spinel-structured Mn_1.6Zn_0.2Ni_0.6Mg_0.2Al_0.4O₄ high-entropy oxide films. X-ray diffraction results demonstrate that the films possess a polycrystalline spinel phase [...] Read more.

In this work, Mn-Zn-Ni-Mg-Al multi-layer films were annealed in air at different temperatures to form spinel-structured Mn_1.6Zn_0.2Ni_0.6Mg_0.2Al_0.4O₄ high-entropy oxide films. X-ray diffraction results demonstrate that the films possess a polycrystalline spinel phase as well as impurity phases: when annealed at 650 °C and 750 °C, MnO₂ and Al₂O₃ impurity phases exist; at 950 °C, an Al₂O₃ impurity phase exists. Only at 850 °C does a pure spinel phase exist. However, the film at 750 °C exhibits the best conductive behavior, which indicates that the impurity phases may not have to be removed to maintain the best electrical properties of the film. Full article

(This article belongs to the Special Issue New Technique for Preparing Thin Film: Characteristic and Further Development)

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14 pages, 5465 KiB

Open AccessEditor’s ChoiceArticle

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 712

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, 11006 KiB

Open AccessEditor’s ChoiceArticle

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

Viewed by 597

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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18 pages, 4444 KiB

Open AccessEditor’s ChoiceArticle

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

Viewed by 691

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 KiB

Open AccessEditor’s ChoiceArticle

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 652

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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18 pages, 4439 KiB

Open AccessEditor’s ChoiceArticle

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

Viewed by 584

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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18 pages, 5642 KiB

Open AccessEditor’s ChoiceArticle

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 665

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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16 pages, 2999 KiB

Open AccessEditor’s ChoiceArticle

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

Viewed by 709

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 KiB

Open AccessEditor’s ChoiceArticle

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

Viewed by 725

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, 3418 KiB

Open AccessEditor’s ChoiceArticle

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

Viewed by 745

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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12 pages, 2780 KiB

Open AccessEditor’s ChoiceArticle

Fabrication and Characterization of Flexible CuI-Based Photodetectors on Mica Substrates by a Low-Temperature Solution Process

by Chien-Yie Tsay, Yun-Chi Chen, Hsuan-Meng Tsai and Kai-Hsiang Liao

Materials 2024, 17(20), 5011; https://doi.org/10.3390/ma17205011 - 14 Oct 2024

Viewed by 804

Abstract

Both CuI and CuI:Zn semiconductor thin films, along with MSM-structured UV photodetectors, were prepared on flexible mica substrates at low temperature (150 °C) by a wet chemical method. The two CuI-based films exhibited a polycrystalline phase with an optical bandgap energy close to [...] Read more.

Both CuI and CuI:Zn semiconductor thin films, along with MSM-structured UV photodetectors, were prepared on flexible mica substrates at low temperature (150 °C) by a wet chemical method. The two CuI-based films exhibited a polycrystalline phase with an optical bandgap energy close to 3.0 eV. Hall effect measurements indicated that the CuI thin film sample had p-type conductivity, while the CuI:Zn thin film sample exhibited n-type conductivity, with the latter showing a higher carrier mobility of 14.78 cm²/Vs compared to 7.67 cm²/Vs for the former. The I-V curves of both types of photodetectors showed asymmetric rectification characteristics with rectification ratios at ±3 V of 5.23 and 14.3 for the CuI and CuI:Zn devices, respectively. Flexible CuI:Zn devices exhibited significantly better sensitivity, responsivity, and specific detectivity than CuI devices both before and after static bending tests. It was found that, while the optoelectronic performance of flexible CuI-based photodetectors degraded under tensile stress during static bending tests, they still exhibited good reproducibility and repeatability in their photoresponses. Full article

(This article belongs to the Special Issue Current Research in Thin-Film Deposition: From Principles and Technologies to Film Properties and Applications)

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15 pages, 4643 KiB

Open AccessEditor’s ChoiceArticle

Composites Based on Electrodeposited WO₃ and TiO₂ Nanoparticles for Photoelectrochemical Water Splitting

by Ramunas Levinas, Elizabeth Podlaha, Natalia Tsyntsaru and Henrikas Cesiulis

Materials 2024, 17(19), 4914; https://doi.org/10.3390/ma17194914 - 8 Oct 2024

Viewed by 1020

Abstract

Photoelectrochemically active WO₃ films were fabricated by electrodeposition from an acidic (pH 2), hydrogen-peroxide-containing electrolyte at −0.5 V vs. SCE. WO₃-TiO₂ composites were then synthesized under the same conditions, but with 0.2 g/L of anatase TiO₂ nanoparticles (⌀ [...] Read more.

Photoelectrochemically active WO₃ films were fabricated by electrodeposition from an acidic (pH 2), hydrogen-peroxide-containing electrolyte at −0.5 V vs. SCE. WO₃-TiO₂ composites were then synthesized under the same conditions, but with 0.2 g/L of anatase TiO₂ nanoparticles (⌀ 36 nm), mechanically suspended in the solution by stirring. After synthesis, the films were annealed at 400 °C. Structural characterization by XRD showed that the WO₃ films exhibit the crystalline structure of a non-stoichiometric hydrate, whereas, in WO₃-TiO₂, the WO₃ phase was monoclinic. The oxidation of tungsten, as revealed by XPS, was W⁶⁺ for both materials. Ti was found to exist mainly as Ti⁴⁺ in the composite, with a weak Ti³⁺ signal. The efficiency of the WO₃ films and composites as an oxygen evolution reaction (OER) photo-electrocatalyst was examined. The composite would generate approximately three times larger steady-state photocurrents at 1.2 V vs. SCE in a neutral 0.5 M Na₂SO₄ electrolyte compared to WO₃ alone. The surface recombination of photogenerated electron–hole pairs was characterized by intensity-modulated photocurrent spectroscopy (IMPS). Photogenerated charge transfer efficiencies were calculated from the spectra, and at 1.2 V vs. SCE, were 86.6% for WO₃ and 62% for WO₃-TiO₂. Therefore, the composite films suffered from relatively more surface recombination but generated larger photocurrents, which resulted in overall improved photoactivity. Full article

(This article belongs to the Special Issue Electrochemical Material Science and Electrode Processes)

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26 pages, 9412 KiB

Open AccessEditor’s ChoiceArticle

Mechanisms of Chemically Promoted Material Removal Examined for Molybdenum and Copper CMP in Weakly Alkaline Citrate-Based Slurries

by K. U. Gamagedara and D. Roy

Materials 2024, 17(19), 4905; https://doi.org/10.3390/ma17194905 - 7 Oct 2024

Cited by 1 | Viewed by 1585

Abstract

Chemical mechanical planarization (CMP) of metal components is an essential step in the fabrication of integrated circuits. Metal CMP is a complex process where strategically activated (electro)chemical reactions serve to structurally weaken the surface layers of the material being processed, and the resulting [...] Read more.

Chemical mechanical planarization (CMP) of metal components is an essential step in the fabrication of integrated circuits. Metal CMP is a complex process where strategically activated (electro)chemical reactions serve to structurally weaken the surface layers of the material being processed, and the resulting overburdens are removed under low-force abrasion. Understanding the tribo-electrochemical mechanisms of this process is crucial to successfully designing the consumable materials for advanced CMP slurries that are needed for the new technology nodes. Using a model CMP system involving copper (wiring material in interconnect structures) and molybdenum (a new diffusion barrier material for copper), the present work illustrates a tribo-electroanalytical scheme for studying various mechanistic details of metal CMP. Electroanalytical probes are employed both in the absence and in the presence of surface polishing to quantify the interplay between mechanical abrasion and chemical surface modification. Weakly alkaline slurry formulations are tested with variable concentrations of silica abrasives and a complexing agent, citric acid. The results serve to examine the link between material removal and tribo-corrosion and to identify the functions of the active slurry additives in governing the rates and selectivity of material removal for CMP. Full article

(This article belongs to the Section Materials Chemistry)

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35 pages, 4084 KiB

Open AccessEditor’s ChoiceArticle

Electrostatically Interacting Wannier Qubits in Curved Space

by Krzysztof Pomorski

Materials 2024, 17(19), 4846; https://doi.org/10.3390/ma17194846 - 30 Sep 2024

Cited by 2 | Viewed by 1084

Abstract

A derivation of a tight-binding model from Schrödinger formalism for various topologies of position-based semiconductor qubits is presented in the case of static and time-dependent electric fields. The simplistic tight-binding model enables the description of single-electron devices at a large integration scale. The [...] Read more.

A derivation of a tight-binding model from Schrödinger formalism for various topologies of position-based semiconductor qubits is presented in the case of static and time-dependent electric fields. The simplistic tight-binding model enables the description of single-electron devices at a large integration scale. The case of two electrostatically Wannier qubits (also known as position-based qubits) in a Schrödinger model is presented with omission of spin degrees of freedom. The concept of programmable quantum matter can be implemented in the chain of coupled semiconductor quantum dots. Highly integrated and developed cryogenic CMOS nanostructures can be mapped to coupled quantum dots, the connectivity of which can be controlled by a voltage applied across the transistor gates as well as using an external magnetic field. Using the anti-correlation principle arising from the Coulomb repulsion interaction between electrons, one can implement classical and quantum inverters (Classical/Quantum Swap Gate) and many other logical gates. The anti-correlation will be weakened due to the fact that the quantumness of the physical process brings about the coexistence of correlation and anti-correlation at the same time. One of the central results presented in this work relies on the appearance of dissipation-like processes and effective potential renormalization building effective barriers in both semiconductors and in superconductors between not bended nanowire regions both in classical and in quantum regimes. The presence of non-straight wire regions is also expressed by the geometrical dissipative quantum Aharonov–Bohm effect in superconductors/semiconductors when one obtains a complex value vector potential-like field. The existence of a Coulomb interaction provides a base for the physical description of an electrostatic Q-Swap gate with any topology using open-loop nanowires, with programmable functionality. We observe strong localization of the wavepacket due to nanowire bending. Therefore, it is not always necessary to build a barrier between two nanowires to obtain two quantum dot systems. On the other hand, the results can be mapped to the problem of an electron in curved space, so they can be expressed with a programmable position-dependent metric embedded in Schrödinger’s equation. The semiconductor quantum dot system is capable of mimicking curved space, providing a bridge between fundamental and applied science in the implementation of single-electron devices. Full article

(This article belongs to the Section Quantum Materials)

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9 pages, 1716 KiB

Open AccessEditor’s ChoiceArticle

Adsorption and Catalytic Reduction of Nitrogen Oxides (NO, N₂O) on Disulfide Cluster Complexes of Cobalt and Iron—A Density Functional Study

by Ellie L. Uzunova and Ivelina M. Georgieva

Materials 2024, 17(19), 4764; https://doi.org/10.3390/ma17194764 - 28 Sep 2024

Viewed by 734

Abstract

The reactivity of nitrogen oxide, NO, as a ligand in complexes with [Fe2-S2] and [Co2-S2] non-planar rhombic cores is examined by density functional theory (DFT). The cobalt-containing nitrosyl complexes are less stable than the iron complexes because the Co-S bonds in the [Co2-S2] [...] Read more.

The reactivity of nitrogen oxide, NO, as a ligand in complexes with [Fe2-S2] and [Co2-S2] non-planar rhombic cores is examined by density functional theory (DFT). The cobalt-containing nitrosyl complexes are less stable than the iron complexes because the Co-S bonds in the [Co2-S2] core are weakened upon NO coordination. Various positions of NO were examined, including its binding to sulfur centers. The release of NO molecules can be monitored photochemically. The ability of NO to form a (NO)₂ dimer provides a favorable route of electrochemical reduction, as protonation significantly stabilizes the dimeric species over the monomers. The quasilinear dimer ONNO, with trans-orientation of oxygen atoms, gains higher stability under protonation and reduction via proton–electron transfer. The first two reduction steps lead to an N₂O intermediate, whose reduction is more energy demanding: in the two latter reaction steps the highest energy barrier for Co₂S₂(CO)₆ is 109 kJ mol⁻¹, and for Fe₂S₂(CO)₆, it is 133 kJ mol⁻¹. Again, the presence of favorable light absorption bands allows for a photochemical route to overcome these energy barriers. All elementary steps are exothermic, and the final products are molecular nitrogen and water. Full article

(This article belongs to the Special Issue Transition Metal Nanomaterials: Synthesis and Photo/Electrocatalytic Performance)

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30 pages, 13814 KiB

Open AccessEditor’s ChoiceReview

Advances in Resistance Welding of Fiber-Reinforced Thermoplastics

by Zhanyi Geng, Shibao Yu, Shiyuan Wang, Zengtai Tian, Zhonglin Gao, Kaifeng Wang and Yang Li

Materials 2024, 17(19), 4693; https://doi.org/10.3390/ma17194693 - 24 Sep 2024

Viewed by 1263

Abstract

Fiber-reinforced thermoplastics (FRTPs) have become a new generation of lightweight materials due to their superior mechanical properties, good weldability and environmental resistance, potential for recycling, etc. The market for FRTPs is expected to grow at a compound annual growth rate (CAGR) of 7.8% [...] Read more.

Fiber-reinforced thermoplastics (FRTPs) have become a new generation of lightweight materials due to their superior mechanical properties, good weldability and environmental resistance, potential for recycling, etc. The market for FRTPs is expected to grow at a compound annual growth rate (CAGR) of 7.8% from 2022 to 2030. Many researchers have been trying to solve the problems in their processing and joining process, and gradually expand their application. Resistance welding is one of the most suitable techniques to join FRTPs. This paper summarizes the research progress of FRTP resistance welding in terms of the basic process of FRTP resistance welding, factors affecting joint performance, joint failure behavior, numerical simulation, weld quality control, and resistance welding of thermoplastic/thermoset composites. The objective of this paper is to provide a deeper insight into the knowledge of FRTP resistance welding and provide reference for the further development and application of FRTP resistance welding. Full article

(This article belongs to the Special Issue Advanced Welding in Alloys and Composites)

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13 pages, 5692 KiB

Open AccessEditor’s ChoiceArticle

Experimental Investigation of the Impact of Loading Conditions on the Change in Thin NiTi Wire Resistance during Cyclic Stretching

by Jonasz Hartwich, Sławomir Duda, Sebastian Sławski, Marek Kciuk, Anna Woźniak and Grzegorz Gembalczyk

Materials 2024, 17(18), 4577; https://doi.org/10.3390/ma17184577 - 18 Sep 2024

Viewed by 765

Abstract

This paper presents the results of an experimental study designed to evaluate the effect of repeated stretching cycles on the electrical resistance change in a NiTi alloy wire. In particular, tests were carried out to determine the effect of the type of loading [...] Read more.

This paper presents the results of an experimental study designed to evaluate the effect of repeated stretching cycles on the electrical resistance change in a NiTi alloy wire. In particular, tests were carried out to determine the effect of the type of loading on resistance change in the investigated wires. Wires with a diameter of 100 μm were used in the research. The experiment was carried out on a dedicated test stand designed for this purpose. During the test, the samples were subjected to 40 identical tensile cycles. The electrical resistance, sample elongation, and tensile force during successive stretching cycles were measured. The conducted research demonstrated the impact of elongation and reorientation of the structure on the resistance change in NiTi alloy thin wires. The research included a comparison of the effect of two different types of loading on the electrical resistance change in the sample. During cyclic stretching of a NiTi alloy sample with constant displacement, a decrease in electrical resistance was observed after each successive stretching cycle. Alternatively, when stretching with a constant force, the value of electrical resistance increased. In both types of loads, the greatest change in resistance value was observed at the initial cycles. Full article

(This article belongs to the Special Issue Technology and Applications of Shape Memory Materials)

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20 pages, 7162 KiB

Open AccessEditor’s ChoiceArticle

Homogenization of Thermal Properties in Metaplates

by David Faraci and Claudia Comi

Materials 2024, 17(18), 4557; https://doi.org/10.3390/ma17184557 - 17 Sep 2024

Cited by 1 | Viewed by 758

Abstract

Three-dimensional metamaterials endowed with two-dimensional in-plane periodicity exhibit peculiar thermoelastic behaviour when heated or cooled. By proper design of the unit cell, the equivalent thermal expansion coefficient can be programmed and can also reach negative values. The heterogeneity in the third direction of [...] Read more.

Three-dimensional metamaterials endowed with two-dimensional in-plane periodicity exhibit peculiar thermoelastic behaviour when heated or cooled. By proper design of the unit cell, the equivalent thermal expansion coefficient can be programmed and can also reach negative values. The heterogeneity in the third direction of such metamaterials also causes, in general, a thermal-induced deflection. The prediction of the equivalent thermal properties is important to design the metamaterial suitable for a specific application. Under the hypothesis of small thickness with respect to the global in-plane dimensions, we make use of asymptotic homogenization to describe the thermoelastic behaviour of these metamaterials as that of an equivalent homogenous plate. The method provides explicit expressions for the effective thermal properties, which allow for a cost-effective prediction of the thermoelastic response of these metaplates. Full article

(This article belongs to the Special Issue Advanced Mechanical Design and Applications of Metamaterials)

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147 pages, 22809 KiB

Open AccessEditor’s ChoiceReview

Thin Conducting Films: Preparation Methods, Optical and Electrical Properties, and Emerging Trends, Challenges, and Opportunities

by Razia Khan Sharme, Manuel Quijada, Mauricio Terrones and Mukti M. Rana

Materials 2024, 17(18), 4559; https://doi.org/10.3390/ma17184559 - 17 Sep 2024

Cited by 4 | Viewed by 1953

Abstract

Thin conducting films are distinct from bulk materials and have become prevalent over the past decades as they possess unique physical, electrical, optical, and mechanical characteristics. Comprehending these essential properties for developing novel materials with tailored features for various applications is very important. [...] Read more.

Thin conducting films are distinct from bulk materials and have become prevalent over the past decades as they possess unique physical, electrical, optical, and mechanical characteristics. Comprehending these essential properties for developing novel materials with tailored features for various applications is very important. Research on these conductive thin films provides us insights into the fundamental principles, behavior at different dimensions, interface phenomena, etc. This study comprehensively analyzes the intricacies of numerous commonly used thin conducting films, covering from the fundamentals to their advanced preparation methods. Moreover, the article discusses the impact of different parameters on those thin conducting films’ electronic and optical properties. Finally, the recent future trends along with challenges are also highlighted to address the direction the field is heading towards. It is imperative to review the study to gain insight into the future development and advancing materials science, thus extending innovation and addressing vital challenges in diverse technological domains. Full article

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

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12 pages, 4585 KiB

Open AccessEditor’s ChoiceArticle

Thin-Layer TiO₂ Membrane Fabrication by Condensed Layer Deposition

by Mohammed M. Numaan, Ahmed M. Jasim, Yangchuan Xing and Maria M. Fidalgo

Materials 2024, 17(17), 4436; https://doi.org/10.3390/ma17174436 - 9 Sep 2024

Viewed by 814

Abstract

A novel approach to the fabrication of thin-film supported metal oxide membranes was investigated. Nanocoatings were obtained by the condensed layer deposition of TiO₂ on tubular microporous supports, applying multiple consecutive layers of TiO₂/polyaniline. The surface, cross-sectional structure, and morphology [...] Read more.

A novel approach to the fabrication of thin-film supported metal oxide membranes was investigated. Nanocoatings were obtained by the condensed layer deposition of TiO₂ on tubular microporous supports, applying multiple consecutive layers of TiO₂/polyaniline. The surface, cross-sectional structure, and morphology of the materials were investigated by electron microscopy. Their membrane-related properties were explored by permeability measurements, rejection, and fouling analysis, using polyethylene glycol (PEG) as test molecules. The SEM images showed that TiO₂ was successfully deposited on the surface, creating a layer with partial coverage of the support after each layer was deposited; consequently, the permeability of the membranes decreased gradually. Overall, the results of the flux and permeability of the membranes confirmed the coating. The transmembrane pressure (TMP) increased with each coating layer, while the rejection of the membrane showed gradual improvement. Full article

(This article belongs to the Special Issue Advancements in Thin Film Deposition Technologies)

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13 pages, 4622 KiB

Open AccessEditor’s ChoiceArticle

Diphenylamino-Modified Neutral Pt(II) Complexes: Their Aggregation-Induced Phosphorescent Emission and Picric Acid-Sensing Properties

by Qinglong Zhang, Yingying Yan, Rui Cai, Xiao-Na Li and Chun Liu

Materials 2024, 17(17), 4366; https://doi.org/10.3390/ma17174366 - 3 Sep 2024

Cited by 1 | Viewed by 891

Abstract

Three neutral Pt(II) complexes with diphenylamino-modified 2-phenylpyridine derivatives as cyclometalating ligands and acetylacetone as the ancillary ligand exhibit aggregation-induced phosphorescent emission (AIPE) properties in THF/H₂O. The crystal structures of the complexes highlight the contributions of non-covalent Pt···Pt interactions and hydrogen bonds [...] Read more.

Three neutral Pt(II) complexes with diphenylamino-modified 2-phenylpyridine derivatives as cyclometalating ligands and acetylacetone as the ancillary ligand exhibit aggregation-induced phosphorescent emission (AIPE) properties in THF/H₂O. The crystal structures of the complexes highlight the contributions of non-covalent Pt···Pt interactions and hydrogen bonds to the AIPE properties. These AIPE-active Pt(II) complexes 1–3 have been successfully applied to detect picric acid (PA) in aqueous media, affording the lowest limit of detection at 70 nM. Furthermore, three Pt(II) complexes are able to detect PA in common water samples. The quenching of luminescence in the detection can be attributed to photo-induced electron transfer. Full article

(This article belongs to the Special Issue Advanced Materials for Luminescent Applications)

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18 pages, 3736 KiB

Open AccessEditor’s ChoiceArticle

New Bipolar Host Materials Based on Indolocarbazole for Red Phosphorescent OLEDs

by Sunwoo Park, Hyukmin Kwon, Sangwook Park, Saeyoung Oh, Kiho Lee, Hayoon Lee, Seokwoo Kang, Dongmin Park and Jongwook Park

Materials 2024, 17(17), 4347; https://doi.org/10.3390/ma17174347 - 2 Sep 2024

Viewed by 1223

Abstract

We designed and synthesized new indolocarbazole-triazine derivatives, 9-di-tert-butyl-5,7-bis(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5,7-dihydroindolo[2,3-b]carbazole (2TRZ-P-ICz) and 3,9-di-tert-butyl-5,7-bis(5′-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1′:3′,1″-terphenyl]-2′-yl)-5,7-dihydroindolo[2,3-b]carbazole (2TRZ-TP-ICz), as new bipolar host materials for red phosphorescent OLEDs. In the film state, 2TRZ-P-ICz and 2TRZ-TP-ICz exhibited photoluminescence maxima at 480 nm and 488 nm, respectively. The dipole moment characteristics of [...] Read more.

We designed and synthesized new indolocarbazole-triazine derivatives, 9-di-tert-butyl-5,7-bis(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5,7-dihydroindolo[2,3-b]carbazole (2TRZ-P-ICz) and 3,9-di-tert-butyl-5,7-bis(5′-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1′:3′,1″-terphenyl]-2′-yl)-5,7-dihydroindolo[2,3-b]carbazole (2TRZ-TP-ICz), as new bipolar host materials for red phosphorescent OLEDs. In the film state, 2TRZ-P-ICz and 2TRZ-TP-ICz exhibited photoluminescence maxima at 480 nm and 488 nm, respectively. The dipole moment characteristics of the new compounds under various solvent conditions were investigated using the Lippert–Mataga equation. The results showed that the dipole moment of 2TRZ-P-ICz is 26.9D, while that of 2TRZ-TP-ICz is 21.3D. The delayed fluorescence lifetimes were 0.188 μs for 2TRZ-P-ICz and 2.080 μs for 2TRZ-TP-ICz, with 2TRZ-TP-ICz showing TADF characteristics. Additionally, 2TRZ-TP-ICz was found to have a ΔEST of less than 0.2 eV. The triplet energy levels of the newly synthesized bipolar host materials were found to be 2.72 and 2.75 eV, confirming their suitability for use in red phosphorescent OLEDs. To investigate the carrier mobility of the synthesized materials, hole-only devices and electron-only devices were fabricated and tested. The hole mobility value at 1V was found to be 3.43 × 10⁻³ cm²/Vs for 2TRZ-P-ICz and 2.16 × 10⁻³ cm²/Vs for 2TRZ-TP-ICz. For electron mobility at 1V, 2TRZ-P-ICz showed a value of 4.41 × 10⁻⁹ cm²/Vs, while 2TRZ-TP-ICz exhibited a value of 9.13 × 10⁻⁹ cm²/Vs. As a result, when the new material was used as a host in red phosphorescent OLEDs, 2TRZ-TP-ICz achieved a current efficiency of 9.92 cd/A, an external quantum efficiency of 13.7%, CIE coordinates of (0.679, 0.319), and an electroluminescence maximum wavelength of 626 nm. Full article

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

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14 pages, 5955 KiB

Open AccessEditor’s ChoiceArticle

Prediction of the Interface Behavior of a Steel/CFRP Hybrid Part Manufactured by Stamping

by Jae-Chang Ryu, Chan-Joo Lee, Do-Hoon Shin and Dae-Cheol Ko

Materials 2024, 17(17), 4291; https://doi.org/10.3390/ma17174291 - 30 Aug 2024

Cited by 1 | Viewed by 584

Abstract

Carbon fiber-reinforced plastic (CFRP) is a lightweight material. The automotive industry has focused on producing a steel/CFRP hybrid part to reduce overall weight. After manufacturing, delamination can occur at the interface between the CFRP and steel owing to the hybrid part constituting dissimilar [...] Read more.

Carbon fiber-reinforced plastic (CFRP) is a lightweight material. The automotive industry has focused on producing a steel/CFRP hybrid part to reduce overall weight. After manufacturing, delamination can occur at the interface between the CFRP and steel owing to the hybrid part constituting dissimilar materials. However, most studies have focused only on designing the manufacturing processes for the hybrid part or evaluating the adhesive used at the interface. Therefore, it is necessary to predict the behavior of the interface after demolding the hybrid part. This study aimed to predict the interface behavior of a steel/CFRP hybrid part by considering its forming and cohesive properties. First, double cantilever beam (DCB) and end-notched flexure (ENF) tests were performed to obtain cohesive parameters, such as energy release rate of modes I and II (G_I, G_II). The experimentally obtained properties were applied to the bonding area of the hybrid part. Subsequently, a forming simulation was performed to obtain the stress of the steel blank in the hybrid part. The stress distribution after forming was utilized as the initial condition for spring-back simulation. Finally, the interface behavior of the hybrid part was predicted by a spring-back simulation. The simulation was conducted using the residual stress of steel outer and the cohesive properties on the interface, without the application of any external forces. The cases of spring-back simulation were divided as delamination occurrence and attached state. The simulation results for prediction of delamination occurrence and bonding showed good agreement in both cases with experimental ones. The proposed method would contribute to expanding the manufacturing of the hybrid part by stamping and reducing the manufacturing cost by prediction of delamination occurrence. Full article

(This article belongs to the Special Issue Advances in Hybrid Structure Manufacturing Technology)

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62 pages, 16763 KiB

Open AccessEditor’s ChoiceReview

Epitaxial Growth of Ga₂O₃: A Review

by Imteaz Rahaman, Hunter D. Ellis, Cheng Chang, Dinusha Herath Mudiyanselage, Mingfei Xu, Bingcheng Da, Houqiang Fu, Yuji Zhao and Kai Fu

Materials 2024, 17(17), 4261; https://doi.org/10.3390/ma17174261 - 28 Aug 2024

Cited by 1 | Viewed by 2509

Abstract

Beta-phase gallium oxide (β-Ga₂O₃) is a cutting-edge ultrawide bandgap (UWBG) semiconductor, featuring a bandgap energy of around 4.8 eV and a highly critical electric field strength of about 8 MV/cm. These properties make it highly suitable for next-generation power [...] Read more.

Beta-phase gallium oxide (β-Ga₂O₃) is a cutting-edge ultrawide bandgap (UWBG) semiconductor, featuring a bandgap energy of around 4.8 eV and a highly critical electric field strength of about 8 MV/cm. These properties make it highly suitable for next-generation power electronics and deep ultraviolet optoelectronics. Key advantages of β-Ga₂O₃ include the availability of large-size single-crystal bulk native substrates produced from melt and the precise control of n-type doping during both bulk growth and thin-film epitaxy. A comprehensive understanding of the fundamental growth processes, control parameters, and underlying mechanisms is essential to enable scalable manufacturing of high-performance epitaxial structures. This review highlights recent advancements in the epitaxial growth of β-Ga₂O₃ through various techniques, including Molecular Beam Epitaxy (MBE), Metal-Organic Chemical Vapor Deposition (MOCVD), Hydride Vapor Phase Epitaxy (HVPE), Mist Chemical Vapor Deposition (Mist CVD), Pulsed Laser Deposition (PLD), and Low-Pressure Chemical Vapor Deposition (LPCVD). This review concentrates on the progress of Ga₂O₃ growth in achieving high growth rates, low defect densities, excellent crystalline quality, and high carrier mobilities through different approaches. It aims to advance the development of device-grade epitaxial Ga₂O₃ thin films and serves as a crucial resource for researchers and engineers focused on UWBG semiconductors and the future of power electronics. Full article

(This article belongs to the Section Electronic Materials)

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17 pages, 5827 KiB

Open AccessEditor’s ChoiceArticle

Hydrogen Embrittlement Detection Technology Using Nondestructive Testing for Realizing a Hydrogen Society

by Yamato Abiru, Hiroshi Nishiguchi, Masato Maekawa, Takara Nagata, Toshiya Itaya, Michie Koga and Toshiomi Nishi

Materials 2024, 17(17), 4237; https://doi.org/10.3390/ma17174237 - 27 Aug 2024

Cited by 2 | Viewed by 882

Abstract

Crack detection in high-pressure hydrogen gas components, such as pipes, is crucial for ensuring the safety and reliability of hydrogen infrastructure. This study conducts the nondestructive testing of crack propagation in steel piping under cyclic compressive loads in the presence of hydrogen in [...] Read more.

Crack detection in high-pressure hydrogen gas components, such as pipes, is crucial for ensuring the safety and reliability of hydrogen infrastructure. This study conducts the nondestructive testing of crack propagation in steel piping under cyclic compressive loads in the presence of hydrogen in the material. The specimens were hydrogen-precharged through immersion in a 20 mass% ammonium thiocyanate solution at 40 °C for 72 h. The crack growth rate in hydrogen-precharged specimens was approximately 10 times faster than that in uncharged specimens, with cracks propagating from the inner to outer surfaces of the pipe. The fracture surface morphology differed significantly, with flat surfaces in hydrogen-precharged materials and convex or concave surfaces in uncharged materials. Eddy current and hammering tests revealed differences in the presence of large cracks between the two materials. By contrast, hammering tests revealed differences in the presence of a half size crack between the two materials. These findings highlight the effect of hydrogen precharging on crack propagation in steel piping and underscore the importance of early detection methods. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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11 pages, 4251 KiB

Open AccessEditor’s ChoiceArticle

Evaluating Optical Properties of Mixed-Phase 2D MoSe₂/Poly(vinyl alcohol) Nanocomposite Film

by Suman Chhetri, Anh Tuan Nguyen, Nicolas Gaillard and Woochul Lee

Materials 2024, 17(17), 4178; https://doi.org/10.3390/ma17174178 - 23 Aug 2024

Viewed by 784

Abstract

Highly solar light-absorbing poly(vinyl alcohol) (PVA) nanocomposite films have garnered wide attention in fields such as flexible optoelectronics, solar energy harvesting, and photothermal therapy. However, fabricating PVA nanocomposite films with a broad spectrum of solar absorption using cost-effective and non-toxic nanofillers remains challenging. [...] Read more.

Highly solar light-absorbing poly(vinyl alcohol) (PVA) nanocomposite films have garnered wide attention in fields such as flexible optoelectronics, solar energy harvesting, and photothermal therapy. However, fabricating PVA nanocomposite films with a broad spectrum of solar absorption using cost-effective and non-toxic nanofillers remains challenging. Herein, nanocomposite films of PVA incorporating various concentrations of mixed-phase 2D MoSe₂ nanosheets (i.e., a combination of the 2H and 1T phase) were prepared using a solution casting technique. Scanning electron microscopy (SEM) shows homogenous dispersion of MoSe₂ nanosheets in the PVA matrix even at higher concentrations, while atomic force microscopy (AFM) reveals increasing surface roughness with increasing MoSe₂ content, reaching a plateau after 20 wt%. With the increase in the concentration of MoSe₂, the nanocomposite films exhibit interesting light absorption characteristics reaching their highest absorption (average 94.9%) at 40 wt% MoSe₂. The incorporated mixed-phase MoSe₂ nanosheets induce a significant change in the energy levels of the PVA matrix, which is reflected in the reduced optical band gap energy (2.63 eV) at 40 wt% MoSe₂ against pure PVA (5.28 eV). The excellent light absorption of PVA nanocomposite films across the entire range from 250 nm to 2500 nm is attributed to the thin 2D structure of MoSe₂ and the presence of its mixed phase. Full article

(This article belongs to the Special Issue New Insight into Design and Properties of Nanomaterials (Second Edition))

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11 pages, 1960 KiB

Open AccessEditor’s ChoiceArticle

Silicon Carbide Nanowire Based Integrated Electrode for High Temperature Supercapacitors

by Shiyu Sha, Chang Liang, Songyang Lv, Lin Xu, Defu Sun, Jiayue Yang, Lei Zhang and Shouzhi Wang

Materials 2024, 17(16), 4161; https://doi.org/10.3390/ma17164161 - 22 Aug 2024

Cited by 1 | Viewed by 1227

Abstract

Silicon carbide (SiC) single crystals have great prospects for high-temperature energy storage due to their robust structural stability, ultrahigh power output, and superior temperature stability. However, energy density is an essential challenge for SiC-based devices. Herein, a facile two-step strategy is proposed for [...] Read more.

Silicon carbide (SiC) single crystals have great prospects for high-temperature energy storage due to their robust structural stability, ultrahigh power output, and superior temperature stability. However, energy density is an essential challenge for SiC-based devices. Herein, a facile two-step strategy is proposed for the large-scale synthesis of a unique architecture of SiC nanowires incorporating MnO₂ for enhanced supercapacitors (SCs), arising from the synergy effect between the SiC nanowires as a highly conductive skeleton and the MnO₂ with numerous active sites. The SiC@MnO₂ integrated electrode-based SCs with ionic liquid (IL) electrolytes were assembled and delivered outstanding energy and power density, as well as a great lifespan at 150 °C. This impressive work offers a novel avenue for the practical application of SiC-based electrochemical energy storage devices with high energy density under high temperatures. Full article

(This article belongs to the Special Issue Research Progress of Advanced Crystals: Growth and Doping)

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15 pages, 6460 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of the Properties of 3D-Printed Onyx–Fiberglass Composites

by Jong-Hwan Yun, Gun-Woong Yoon, Yu-Jae Jeon and Min-Soo Kang

Materials 2024, 17(16), 4140; https://doi.org/10.3390/ma17164140 - 21 Aug 2024

Viewed by 1241

Abstract

This study evaluated the properties of 3D-printed Onyx–fiberglass composites. These composites were 3D-printed with zero, one, two, three, and four layers of fiberglass. Ten samples of each configuration were printed for the tensile and flexural tests. The average tensile strength of the Onyx [...] Read more.

This study evaluated the properties of 3D-printed Onyx–fiberglass composites. These composites were 3D-printed with zero, one, two, three, and four layers of fiberglass. Ten samples of each configuration were printed for the tensile and flexural tests. The average tensile strength of the Onyx specimens was calculated to be 44.79 MPa, which increased linearly by approximately 20–25 MPa with each additional fiberglass layer. The elastic moduli calculated from the micromechanics models were compared with the experimental values obtained from the tensile tests. The experimental elastic modulus increased more significantly than the model prediction when more fiberglass layers were added. The flexural modulus of Onyx was 17.6 GPa, which increased with each additional fiberglass layer. This quantitative analysis of composites fabricated using 3D printing highlights their potential for commercialization and industrial applications. Full article

(This article belongs to the Section Advanced Composites)

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24 pages, 13126 KiB

Open AccessEditor’s ChoiceArticle

Forced-Vibration Characteristics of Bowtie-Shaped Honeycomb Composite Sandwich Panel with Viscoelastic Damping Layer

by Siqi Miao, Yifeng Zhong, Mingtao Zhang and Rong Liu

Materials 2024, 17(16), 4067; https://doi.org/10.3390/ma17164067 - 16 Aug 2024

Viewed by 939

Abstract

The incorporation of viscoelastic layers in laminates can markedly enhance the damped dynamic characteristics. This study focuses on integrating viscoelastic layers into the composite facesheet of the bowtie-shaped honeycomb core composite sandwich panel (BHC-CSP). The homogenization of the damped BHC-CSP is performed by [...] Read more.

The incorporation of viscoelastic layers in laminates can markedly enhance the damped dynamic characteristics. This study focuses on integrating viscoelastic layers into the composite facesheet of the bowtie-shaped honeycomb core composite sandwich panel (BHC-CSP). The homogenization of the damped BHC-CSP is performed by employing the variational asymptotic method. Based on the generalized total energy equation, the energy functional of the representative unit cell of the damped BHC-CSP is asymptotically analyzed. The warping function, derived following the principle of minimum potential energy, provides a basis for obtaining the corresponding Euler–Lagrange equation to ascertain the equivalent elastic properties of the damped BHC-CSP. Utilizing the developed two-dimensional equivalent model, the free-vibration characteristics of the damped BHC-CSP are examined across diverse boundary conditions while delving into the impact of an external viscous damping layer on the natural frequency of the damped BHC-CSP. The results reveal that intensified boundary constraints effectively diminish the effective vibration region of the damped BHC-CSP, thereby enhancing its overall stability. The introduction of a PMI foam layer proves effective in adjusting the stiffness and mass distribution of the damped BHC-CSP. Resonance characteristics are explored through frequency and time-domain analyses, highlighting the pivotal roles of the excitation position and receiver point in influencing the displacement and velocity responses. Although the stiffness is improved by incorporating a PMI foam layer, its effect on the damping performance of the damped BHC-CSP is minimal when compared to the T-SW308 foam layer. Full article

(This article belongs to the Section Advanced Composites)

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19 pages, 5935 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Towards the Reuse of Fire Retarded Polyamide 12 for Laser Sintering

by Dylan Seigler, Marcos Batistella and José-Marie Lopez-Cuesta

Materials 2024, 17(16), 4064; https://doi.org/10.3390/ma17164064 - 15 Aug 2024

Viewed by 816

Abstract

The control of powder aging during Selective Laser Sintering (SLS) processing is one of the challenges to be overcome for the implementation of this technique in serial production. Aging phenomena, because of the elevated temperatures and long processing times, need to be considered [...] Read more.

The control of powder aging during Selective Laser Sintering (SLS) processing is one of the challenges to be overcome for the implementation of this technique in serial production. Aging phenomena, because of the elevated temperatures and long processing times, need to be considered when a fraction of the polymer powders present in the build chamber and not used to manufacture the parts are reused at various times. The aim of this study was to investigate the influence of successive reuse of blends of pure Polyamide 12 and its blends with two types of flame retardants (FR): ammonium polyphosphate (APP) and zinc borate (ZB). The composition of the blends was 70/30 (wt/wt) PA 12/FR. Four successive processing stages have been carried out by collecting the remaining powder blend each time. The powders were re-used using the same processing parameters after sieving. DSC measurements showed that the incorporation of FRs entailed a reduction in the processing window up to 4 °C; nevertheless, no further reduction was noted after aging. The TGA curves of aged blends of powders were also similar for pure PA 12 and PA 12 with FR. In addition, initial and reused powders presented a higher degree of crystallinity than the specimens processed from the powders. The heterogeneous character of the PA 12 after LS processing or reprocessing was shown through Pyrolysis Combustion Flow Calorimetry (PCFC) and cone calorimeter (CC) tests. FTIR analysis also showed that post-condensation reactions have occurred. The mode of action of the flame retardants was clearly seen on HRR curves at both tests. The first reuses of PA 12 powders entailed a significant reduction in time to ignition at the cone calorimeter (150 for the initial material to around 90 s for the reused material), indicating the formation of short polymer chains. Only in the case of zinc borate was it noticed that re-used powder was detrimental to the fire performance because of a strong increase in the value of pHRR (between 163 and 220 kW/m² for reused material instead of 125 kW/m² for the initial one). Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing-3rd Edition)

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27 pages, 6259 KiB

Open AccessEditor’s ChoiceArticle

Real-Time Spectroscopic Ellipsometry for Flux Calibrations in Multi-Source Co-Evaporation of Thin Films: Application to Rate Variations in CuInSe₂ Deposition

by Dhurba R. Sapkota, Balaji Ramanujam, Puja Pradhan, Mohammed A. Razooqi Alaani, Ambalanath Shan, Michael J. Heben, Sylvain Marsillac, Nikolas J. Podraza and Robert W. Collins

Materials 2024, 17(16), 4048; https://doi.org/10.3390/ma17164048 - 14 Aug 2024

Viewed by 822

Abstract

Flux calibrations in multi-source thermal co-evaporation of thin films have been developed based on real-time spectroscopic ellipsometry (RTSE) measurements. This methodology has been applied to fabricate CuInSe₂ (CIS) thin film photovoltaic (PV) absorbers, as an illustrative example, and their properties as functions [...] Read more.

Flux calibrations in multi-source thermal co-evaporation of thin films have been developed based on real-time spectroscopic ellipsometry (RTSE) measurements. This methodology has been applied to fabricate CuInSe₂ (CIS) thin film photovoltaic (PV) absorbers, as an illustrative example, and their properties as functions of deposition rate have been studied. In this example, multiple Cu layers are deposited step-wise onto the same Si wafer substrate at different Cu evaporation source temperatures (T_Cu). Multiple In₂Se₃ layers are deposited similarly at different In source temperatures (T_In). Using RTSE, the Cu and In₂Se₃ deposition rates are determined as functions of T_Cu and T_In. These rates, denoted R_eff, are measured in terms of effective thickness which is the volume per planar substrate area and accounts for surface roughness variations with deposition time. By assuming that all incident metal atoms are incorporated into the films and that the atomic concentrations in the deposited material components are the same as in single crystals, initial estimates of the Cu and In atom fluxes can be made versus T_Cu and T_In. Applying these estimates to the co-evaporation of a set of CIS films from individual Cu, In, and Se sources, atomic concentration corrections can be assigned to the Cu and In₂Se₃ calibration films. The corrections enable generation of a novel calibration diagram predicting the atomic ratio y = [Cu]/[In] and rate R_eff within the T_Cu-T_In plane. Using this diagram, optimization of the CIS properties as a PV absorber can be achieved versus both y and R_eff. Full article

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

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17 pages, 5617 KiB

Open AccessEditor’s ChoiceArticle

Impact of Thermochemical Treatments on Electrical Conductivity of Donor-Doped Strontium Titanate Sr(Ln)TiO₃ Ceramics

by Aleksandr Bamburov, Ekaterina Kravchenko and Aleksey A. Yaremchenko

Materials 2024, 17(15), 3876; https://doi.org/10.3390/ma17153876 - 5 Aug 2024

Viewed by 1034

Abstract

The remarkable stability, suitable thermomechanical characteristics, and acceptable electrical properties of donor-doped strontium titanates make them attractive materials for fuel electrodes, interconnects, and supports of solid oxide fuel and electrolysis cells (SOFC/SOEC). The present study addresses the impact of processing and thermochemical treatment [...] Read more.

The remarkable stability, suitable thermomechanical characteristics, and acceptable electrical properties of donor-doped strontium titanates make them attractive materials for fuel electrodes, interconnects, and supports of solid oxide fuel and electrolysis cells (SOFC/SOEC). The present study addresses the impact of processing and thermochemical treatment conditions on the electrical conductivity of SrTiO₃-derived ceramics with moderate acceptor-type substitution in a strontium sublattice. A-site-deficient Sr_0.85La_0.10TiO_3−δ and cation-stoichiometric Sr_0.85Pr_0.15TiO_3+δ ceramics with varying microstructures and levels of reduction have been prepared and characterized by XRD, SEM, TGA, and electrical conductivity measurements under reducing conditions. The analysis of the collected data suggested that the reduction process of dense donor-doped SrTiO₃ ceramics is limited by sluggish oxygen diffusion in the crystal lattice even at temperatures as high as 1300 °C. A higher degree of reduction and higher electrical conductivity can be obtained for porous structures under similar thermochemical treatment conditions. Metallic-like conductivity in dense reduced Sr_0.85La_0.10TiO_3−δ corresponds to the state quenched from the processing temperature and is proportional to the concentration of Ti³⁺ in the lattice. Due to poor oxygen diffusivity in the bulk, dense Sr_0.85La_0.10TiO_3−δ ceramics remain redox inactive and maintain a high level of conductivity under reducing conditions at temperatures below 1000 °C. While the behavior and properties of dense reduced Sr_0.85Pr_0.15TiO_3+δ ceramics with a large grain size (10–40 µm) were found to be similar, decreasing grain size down to 1–3 µm results in an increasing role of resistive grain boundaries which, regardless of the degree of reduction, determine the semiconducting behavior and lower total electrical conductivity of fine-grained Sr_0.85Pr_0.15TiO_3+δ ceramics. Oxidized porous Sr_0.85Pr_0.15TiO_3+δ ceramics exhibit faster kinetics of reduction compared to the Sr_0.85La_0.10TiO_3−δ counterpart at temperatures below 1000 °C, whereas equilibration kinetics of porous Sr_0.85La_0.10TiO_3−δ structures can be facilitated by reductive pre-treatments at elevated temperatures. Full article

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

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28 pages, 16553 KiB

Open AccessEditor’s ChoiceReview

Progress in Additive Manufacturing of Magnesium Alloys: A Review

by Jiayu Chen and Bin Chen

Materials 2024, 17(15), 3851; https://doi.org/10.3390/ma17153851 - 3 Aug 2024

Cited by 6 | Viewed by 2919

Abstract

Magnesium alloys, renowned for their lightweight yet high-strength characteristics, with exceptional mechanical properties, are highly coveted for numerous applications. The emergence of magnesium alloy additive manufacturing (Mg AM) has further propelled their popularity, offering advantages such as unparalleled precision, swift production rates, enhanced [...] Read more.

Magnesium alloys, renowned for their lightweight yet high-strength characteristics, with exceptional mechanical properties, are highly coveted for numerous applications. The emergence of magnesium alloy additive manufacturing (Mg AM) has further propelled their popularity, offering advantages such as unparalleled precision, swift production rates, enhanced design freedom, and optimized material utilization. This technology holds immense potential in fabricating intricate geometries, complex internal structures, and performance-tailored microstructures, enabling groundbreaking applications. In this paper, we delve into the core processes and pivotal influencing factors of the current techniques employed in Mg AM, including selective laser melting (SLM), electron beam melting (EBM), wire arc additive manufacturing (WAAM), binder jetting (BJ), friction stir additive manufacturing (FSAM), and indirect additive manufacturing (I-AM). Laser powder bed fusion (LPBF) excels in precision but is limited by a low deposition rate and chamber size; WAAM offers cost-effectiveness, high efficiency, and scalability for large components; BJ enables precise material deposition for customized parts with environmental benefits; FSAM achieves fine grain sizes, low defect rates, and potential for precision products; and I-AM boasts a high build rate and industrial adaptability but is less studied recently. This paper attempts to explore the possibilities and challenges for future research in AM. Among them, two issues are how to mix different AM applications and how to use the integration of Internet technologies, machine learning, and process modeling with AM, which are innovative breakthroughs in AM. Full article

(This article belongs to the Special Issue 3D Printing Technology with Metal Materials)

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12 pages, 3470 KiB

Open AccessEditor’s ChoiceArticle

Facilely Promoting the Concentration of Baicalin in Polylactic Acid Fiber for UV Shielding and Antibacterial Functions: A Customized and Sustainable Approach

by Yuyang Zhou, Peng Deng and Wei Chen

Materials 2024, 17(15), 3734; https://doi.org/10.3390/ma17153734 - 28 Jul 2024

Cited by 1 | Viewed by 921

Abstract

There is a significant trend towards the integration of natural substances with bio-polymers for fully bio-based functional composites. Polylactic acid is regarded as a promising biodegradable polymer for replacing synthetic polymers. Differing from the case of natural fiber, the incompatibility of polylactic acid [...] Read more.

There is a significant trend towards the integration of natural substances with bio-polymers for fully bio-based functional composites. Polylactic acid is regarded as a promising biodegradable polymer for replacing synthetic polymers. Differing from the case of natural fiber, the incompatibility of polylactic acid with bio-based molecules prevents it from being used to fabricate high-quality sustainable composites. This work presents a simultaneous ultraviolet shielding and antibacterial finishing process of polylactic acid combined with bioactive baicalin and an eco-friendly ester, which is highlighted for (a) the lack of synthetic chemicals involved in such process, (b) adsorption enhancement achieved at a mild temperature, and (c) marginal color change on treated polylactic acid. A response surface methodology was adopted to analyze the impacts of various factors on the baicalin quantity in polylactic acid, and to optimize the treatment condition. The uptake ratio of baicalin in polylactic acid was drastically promoted from 8.5 mg/g to 21.1 mg/g using methyl cinnamate. The response surface methodology based on a central composite design experiment indicated that the usage of baicalin was the most significant factor followed by methyl cinnamate and temperature. After optimization, a very faint color depth of 1.2 was apparent, but UPF 50+ and 92% bacterial reduction could be achieved. In all, the success in strengthening of the functionalities of polylactic acid extends the applications of polylactic acid products. Full article

(This article belongs to the Special Issue Advances in the Sustainable Fabrication of Smart and Functional Textiles)

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21 pages, 1925 KiB

Open AccessEditor’s ChoiceReview

Machine Learning for Additive Manufacturing of Functionally Graded Materials

by Mohammad Karimzadeh, Deekshith Basvoju, Aleksandar Vakanski, Indrajit Charit, Fei Xu and Xinchang Zhang

Materials 2024, 17(15), 3673; https://doi.org/10.3390/ma17153673 - 25 Jul 2024

Cited by 8 | Viewed by 1822

Abstract

Additive Manufacturing (AM) is a transformative manufacturing technology enabling direct fabrication of complex parts layer-by-layer from 3D modeling data. Among AM applications, the fabrication of Functionally Graded Materials (FGMs) has significant importance due to the potential to enhance component performance across several industries. [...] Read more.

Additive Manufacturing (AM) is a transformative manufacturing technology enabling direct fabrication of complex parts layer-by-layer from 3D modeling data. Among AM applications, the fabrication of Functionally Graded Materials (FGMs) has significant importance due to the potential to enhance component performance across several industries. FGMs are manufactured with a gradient composition transition between dissimilar materials, enabling the design of new materials with location-dependent mechanical and physical properties. This study presents a comprehensive review of published literature pertaining to the implementation of Machine Learning (ML) techniques in AM, with an emphasis on ML-based methods for optimizing FGMs fabrication processes. Through an extensive survey of the literature, this review article explores the role of ML in addressing the inherent challenges in FGMs fabrication and encompasses parameter optimization, defect detection, and real-time monitoring. The article also provides a discussion of future research directions and challenges in employing ML-based methods in the AM fabrication of FGMs. Full article

(This article belongs to the Special Issue Artificial Intelligence in Materials Science and Engineering)

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15 pages, 3035 KiB

Open AccessEditor’s ChoiceArticle

Fiber-Reinforced Equibiaxial Dielectric Elastomer Actuator for Out-of-Plane Displacement

by Simon Holzer, Stefania Konstantinidi, Markus Koenigsdorff, Thomas Martinez, Yoan Civet, Gerald Gerlach and Yves Perriard

Materials 2024, 17(15), 3672; https://doi.org/10.3390/ma17153672 - 25 Jul 2024

Cited by 1 | Viewed by 1073

Abstract

Dielectric elastomer actuators (DEAs) have gained significant attention due to their potential in soft robotics and adaptive structures. However, their performance is often limited by their in-plane strain distribution and limited mechanical stability. We introduce a novel design utilizing fiber reinforcement to address [...] Read more.

Dielectric elastomer actuators (DEAs) have gained significant attention due to their potential in soft robotics and adaptive structures. However, their performance is often limited by their in-plane strain distribution and limited mechanical stability. We introduce a novel design utilizing fiber reinforcement to address these challenges. The fiber reinforcement provides enhanced mechanical integrity and improved strain distribution, enabling efficient energy conversion and out-of-plane displacement. We discuss an analytical model and the fabrication process, including material selection, to realize fiber-reinforced DEAs. Numerical simulations and experimental results demonstrate the performance of the fiber-reinforced equibiaxial DEAs and characterize their displacement and force capabilities. Actuators with four and eight fibers are fabricated with 100

μ

m and 200

μ

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

μ

m is reached, with a force of 0.18 N, showing promise for the development of haptic devices. Full article

(This article belongs to the Special Issue Interactive Fiber Rubber Composites—Volume II)

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22 pages, 6905 KiB

Open AccessEditor’s ChoiceArticle

Dimensional Accuracy of Different Three-Dimensional Printing Models as a Function of Varying the Printing Parameters

by Christin Arnold, Lea Riß, Jeremias Hey and Ramona Schweyen

Materials 2024, 17(14), 3616; https://doi.org/10.3390/ma17143616 - 22 Jul 2024

Viewed by 1135

Abstract

Even in digital workflows, models are required for fitting during the fabrication of dental prostheses. This study examined the influence of different parameters on the dimensional accuracy of three-dimensionally printed models. A stereolithographic data record was generated from a master model (SOLL). With [...] Read more.

Even in digital workflows, models are required for fitting during the fabrication of dental prostheses. This study examined the influence of different parameters on the dimensional accuracy of three-dimensionally printed models. A stereolithographic data record was generated from a master model (SOLL). With digital light processing (DLP) and stereolithography (SLA) printing systems, 126 models were produced in several printing runs—SolFlex350 (S) (DLP, n = 24), CaraPrint 4.0 (C) (DLP, n = 48) and Form2 (F) (SLA, n = 54)—and their accuracy was compared with plaster and milled polyurethane models. In addition to the positioning on the build platform, a distinction was made between parallel and across arrangement of the models to the printer’s front, solid and hollow models, and printing with and without support structures. For accuracy assessment, five measurement sections were defined on the model (A–E) and measured using a calibrated digital calliper and digital scans in combination with the GOM Inspect Professional software 2021. The mean deviation between the measurement methods for all distances was 79 µm. The mean deviation of the models from the digital SOLL model were 207.1 µm for the S series, 25.1 µm for the C series and 141.8 µm for the F series. While positioning did not have an influence, there were clinically relevant differences mainly regarding the choice of printer, but also individually in alignment, model structure and support structures. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing and Application)

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12 pages, 14655 KiB

Open AccessEditor’s ChoiceArticle

Configurational Isomerism in Bimetallic Decametalates

by Aleksandar Kondinski

Materials 2024, 17(14), 3624; https://doi.org/10.3390/ma17143624 - 22 Jul 2024

Viewed by 705

Abstract

In this work, we report on the development of a computational algorithm that explores the configurational isomer space of bimetallic decametalates with general formula

{[M_{x} M_{10 - x}^{'} O_{28}]}^{q}

. For x being a natural number in the [...] Read more.

In this work, we report on the development of a computational algorithm that explores the configurational isomer space of bimetallic decametalates with general formula

{[M_{x} M_{10 - x}^{'} O_{28}]}^{q}

. For x being a natural number in the range of 0 to 10, the algorithm identifies 318 unique configurational isomers. The algorithm is used to generate mixed molybdenum(VI)–vanadium(V) systems

{[{Mo}_{x} V_{10 - x} O_{28}]}^{8 -}

for

x = 0, 1, 2,

and 3 that are of experimental relevance. The application of the density functional theory (DFT) effectively predicts stability trends that correspond well with empirical observations. In dimolybdenum-substituted decavanadate systems, we discover that a two-electron reduction preferentially stabilizes a configurational isomer due to the formation of metal–metal bonding. The particular polyoxometalate structure is of interest for further experimental studies. Full article

(This article belongs to the Special Issue From Molecular to Supramolecular Materials)

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15 pages, 10388 KiB

Open AccessEditor’s ChoiceArticle

Shear Thickening Fluid and Sponge-Hybrid Triboelectric Nanogenerator for a Motion Sensor Array-Based Lying State Detection System

by Youngsu Kim, Inkyum Kim, Maesoon Im and Daewon Kim

Materials 2024, 17(14), 3536; https://doi.org/10.3390/ma17143536 - 17 Jul 2024

Cited by 2 | Viewed by 1322

Abstract

Issues of size and power consumption in IoT devices can be addressed through triboelectricity-driven energy harvesting technology, which generates electrical signals without external power sources or batteries. This technology significantly reduces the complexity of devices, enhances installation flexibility, and minimizes power consumption. By [...] Read more.

Issues of size and power consumption in IoT devices can be addressed through triboelectricity-driven energy harvesting technology, which generates electrical signals without external power sources or batteries. This technology significantly reduces the complexity of devices, enhances installation flexibility, and minimizes power consumption. By utilizing shear thickening fluid (STF), which exhibits variable viscosity upon external impact, the sensitivity of triboelectric nanogenerator (TENG)-based sensors can be adjusted. For this study, the highest electrical outputs of STF and sponge-hybrid TENG (SSH-TENG) devices under various input forces and frequencies were generated with an open-circuit voltage (V_OC) of 98 V and a short-circuit current (I_SC) of 4.5 µA. The maximum power density was confirmed to be 0.853 mW/m² at a load resistance of 30 MΩ. Additionally, a lying state detection system for use in medical settings was implemented using SSH-TENG as a hybrid triboelectric motion sensor (HTMS). Each unit of a 3 × 2 HTMS array, connected to a half-wave rectifier and 1 MΩ parallel resistor, was interfaced with an MCU. Real-time detection of the patient’s condition through the HTMS array could enable the early identification of hazardous situations and alerts. The proposed HTMS continuously monitors the patient’s movements, promptly identifying areas prone to pressure ulcers, thus effectively contributing to pressure ulcer prevention. Full article

(This article belongs to the Special Issue Nanoarchitectonics in Materials Science)

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16 pages, 2959 KiB

Open AccessEditor’s ChoiceArticle

Novel Collagen Membrane Formulations with Irinotecan or Minocycline for Potential Application in Brain Cancer

by Andreea-Anamaria Idu, Mădălina Georgiana Albu Kaya, Ileana Rău, Nicoleta Radu, Cristina-Elena Dinu-Pîrvu and Mihaela Violeta Ghica

Materials 2024, 17(14), 3510; https://doi.org/10.3390/ma17143510 - 15 Jul 2024

Viewed by 1113

Abstract

Our study explores the development of collagen membranes with integrated minocycline or irinotecan, targeting applications in tissue engineering and drug delivery systems. Type I collagen, extracted from bovine skin using advanced fibril-forming technology, was crosslinked with glutaraldehyde to create membranes. These membranes incorporated [...] Read more.

Our study explores the development of collagen membranes with integrated minocycline or irinotecan, targeting applications in tissue engineering and drug delivery systems. Type I collagen, extracted from bovine skin using advanced fibril-forming technology, was crosslinked with glutaraldehyde to create membranes. These membranes incorporated minocycline, an antibiotic, or irinotecan, a chemotherapeutic agent, in various concentrations. The membranes, varying in drug concentration, were studied by water absorption and enzymatic degradation tests, demonstrating a degree of permeability. We emphasize the advantages of local drug delivery for treating high-grade gliomas, highlighting the targeted approach’s efficacy in reducing systemic adverse effects and enhancing drug bioavailability at the tumor site. The utilization of collagen membranes is proposed as a viable method for local drug delivery. Irinotecan’s mechanism, a topoisomerase I inhibitor, and minocycline’s broad antibacterial spectrum and inhibition of glial cell-induced membrane degradation are discussed. We critically examine the challenges posed by the systemic administration of chemotherapeutic agents, mainly due to the blood–brain barrier’s restrictive nature, advocating for local delivery methods as a more effective alternative for glioblastoma treatment. These local delivery strategies, including collagen membranes, are posited as significant advancements in enhancing therapeutic outcomes for glioblastoma patients. Full article

(This article belongs to the Special Issue Novel Green Nanotechnologies Applied in Environmental Protection and Health)

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15 pages, 2643 KiB

Open AccessEditor’s ChoiceArticle

Mechanical and Antimicrobial Properties of the Graphene-Polyamide 6 Composite

by Paweł Głuchowski, Marta Macieja, Robert Tomala, Mariusz Stefanski, Wiesław Stręk, Maciej Ptak, Damian Szymański, Konrad Szustakiewicz, Adam Junka and Bartłomiej Dudek

Materials 2024, 17(14), 3465; https://doi.org/10.3390/ma17143465 - 12 Jul 2024

Cited by 1 | Viewed by 1010

Abstract

This paper presents the synthesis and characterization of graphene–polymer composites, focusing on their mechanical and antibacterial properties. Graphene flakes were obtained via an electrochemical method and integrated into polyamide 6 (PA6) matrices using melt intercalation. Various characterization techniques confirmed the quality of the [...] Read more.

This paper presents the synthesis and characterization of graphene–polymer composites, focusing on their mechanical and antibacterial properties. Graphene flakes were obtained via an electrochemical method and integrated into polyamide 6 (PA6) matrices using melt intercalation. Various characterization techniques confirmed the quality of the graphene flakes, including X-ray diffraction (XRD), Raman spectroscopy, and infrared (IR) spectroscopy, as well as scanning and transmission electron microscopy (SEM and TEM) imaging. Mechanical tests showed an increase in the elastic modulus with graphene incorporation, while the impact strength decreased. The SEM analysis highlighted the dispersion of the graphene flakes within the composites and their impact on fracture behavior. Antimicrobial tests demonstrated significant antibacterial properties of the composites, attributed to both oxidative stress and mechanical damage induced by the graphene flakes. The results suggest promising applications for graphene–polymer composites in advanced antimicrobial materials. Full article

(This article belongs to the Special Issue Advances in Polymer Matrix Composites for High Performance Applications)

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