Materials

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

Cited by 1 | Viewed by 1628

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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12 pages, 2749 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Fracture Strength of Milled and 3D-Printed Crown Materials According to Occlusal Thickness

by Yeseul Park, Jimin Kim, You-Jung Kang, Eun-Young Shim and Jee-Hwan Kim

Materials 2024, 17(18), 4645; https://doi.org/10.3390/ma17184645 - 22 Sep 2024

Cited by 3 | Viewed by 2125

Abstract

This study aimed to measure the fracture strengths and hardness of final restorative milled and 3D-printed materials and evaluate the appropriate crown thickness for their clinical use for permanent prosthesis. One type of milled material (group M) and two types of 3D-printed materials [...] Read more.

This study aimed to measure the fracture strengths and hardness of final restorative milled and 3D-printed materials and evaluate the appropriate crown thickness for their clinical use for permanent prosthesis. One type of milled material (group M) and two types of 3D-printed materials (groups P1 and P2) were used. Their crown thickness was set to 0.5, 1.0, and 1.5 mm for each group, and the fracture strength was measured. Vickers hardness was measured and analyzed to confirm the hardness of each material. Scanning electron microscopy was taken to observe the surface changes of the 3D-printed materials under loads of 900 and 1500 N. With increased thickness, the fracture strength significantly increased for group M but significantly decreased for group P1. For group P2, the fracture strengths for the thicknesses of 0.5 mm and 1.5 mm significantly differed, but that for 1.0 mm did not differ from those for other thicknesses. The hardness of group M was significantly higher than that of groups P1 and P2. For all thicknesses, the fracture strength was higher than the average occlusal force for all materials; however, an appropriate crown thickness is required depending on the material and component. Full article

(This article belongs to the Special Issue Advances in New Alloys, Polymers and Composites for Biomedical Applications)

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11 pages, 4905 KiB

Open AccessEditor’s ChoiceArticle

Hierarchically Graphitic Carbon Structure Derived from Metal Ions Impregnated Harmful Inedible Seaweed as Energy-Related Material

by Yun-Mi Song, Hui Gyeong Park and Jung-Soo Lee

Materials 2024, 17(18), 4643; https://doi.org/10.3390/ma17184643 - 21 Sep 2024

Cited by 1 | Viewed by 1435

Abstract

This study explored the development of hierarchical graphitic carbon structures (HGCs) from harmful inedible seaweed waste harvested in the summer. Elevated sea temperatures during the summer increase the cellulose content of seaweeds, making them unsuitable for consumption. By utilizing seaweed biomass, this study [...] Read more.

This study explored the development of hierarchical graphitic carbon structures (HGCs) from harmful inedible seaweed waste harvested in the summer. Elevated sea temperatures during the summer increase the cellulose content of seaweeds, making them unsuitable for consumption. By utilizing seaweed biomass, this study addresses critical marine environmental issues and provides a sustainable solution for promising electrode materials for energy storage devices. The fabrication process involved impregnating seaweed with Ni ions, followed by annealing to create a highly crystalline carbon structure. Subsequent etching produced numerous nano-sized pores and a large surface area (806 m²/g), significantly enhancing the number of electrically active sites. The resulting HGCs exhibited a high capacitance and maintained their capacity even after 10,000 cycles in fast-current systems. This innovative approach not only mitigates the environmental burden of seaweed waste but also offers a sustainable method for converting it into efficient energy storage materials. Full article

(This article belongs to the Special Issue Synthesis and Characterization Techniques for Nanomaterials)

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14 pages, 3909 KiB

Open AccessEditor’s ChoiceArticle

Impact of Annealing in Various Atmospheres on Characteristics of Tin-Doped Indium Oxide Layers towards Thermoelectric Applications

by Anna Kaźmierczak-Bałata, Jerzy Bodzenta, Piotr Szperlich, Marcin Jesionek, Anna Michalewicz, Alina Domanowska, Jeyanthinath Mayandi, Vishnukanthan Venkatachalapathy and Andrej Kuznetsov

Materials 2024, 17(18), 4606; https://doi.org/10.3390/ma17184606 - 20 Sep 2024

Cited by 1 | Viewed by 1219

Abstract

The aim of this work was to investigate the possibility of modifying the physical properties of indium tin oxide (ITO) layers by annealing them in different atmospheres and temperatures. Samples were annealed in vacuum, air, oxygen, nitrogen, carbon dioxide and a mixture of [...] Read more.

The aim of this work was to investigate the possibility of modifying the physical properties of indium tin oxide (ITO) layers by annealing them in different atmospheres and temperatures. Samples were annealed in vacuum, air, oxygen, nitrogen, carbon dioxide and a mixture of nitrogen with hydrogen (NHM) at temperatures from 200 °C to 400 °C. Annealing impact on the crystal structure, optical, electrical, thermal and thermoelectric properties was examined. It has been found from XRD measurements that for samples annealed in air, nitrogen and NHM at 400 °C, the In₂O₃/In₄Sn₃O₁₂ share ratio decreased, resulting in a significant increase of the In₄Sn₃O₁₂ phase. The annealing at the highest temperature in air and nitrogen resulted in larger grains and the mean grain size increase, while vacuum, NHM and carbon dioxide atmospheres caused the decrease in the mean grain size. The post-processing in vacuum and oxidizing atmospheres effected in a drop in optical bandgap and poor electrical properties. The carbon dioxide seems to be an optimal atmosphere to obtain good TE generator parameters—high ZT. The general conclusion is that annealing in different atmospheres allows for controlled changes in the structure and physical properties of ITO layers. Full article

(This article belongs to the Special Issue Disorder-Driven Structure-Property Functionality in Materials: From Material Discovery to Device Development)

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21 pages, 3366 KiB

Open AccessEditor’s ChoiceReview

A Review of the Development of Titanium-Based and Magnesium-Based Metallic Glasses in the Field of Biomedical Materials

by Zeyun Cai, Peng Du, Kun Li, Lina Chen and Guoqiang Xie

Materials 2024, 17(18), 4587; https://doi.org/10.3390/ma17184587 - 19 Sep 2024

Cited by 5 | Viewed by 1974

Abstract

This article reviews the research and development focus of metallic glasses in the field of biomedical applications. Metallic glasses exhibit a short-range ordered and long-range disordered glassy structure at the microscopic level, devoid of structural defects such as dislocations and grain boundaries. Therefore, [...] Read more.

This article reviews the research and development focus of metallic glasses in the field of biomedical applications. Metallic glasses exhibit a short-range ordered and long-range disordered glassy structure at the microscopic level, devoid of structural defects such as dislocations and grain boundaries. Therefore, they possess advantages such as high strength, toughness, and corrosion resistance, combining characteristics of both metals and glasses. This novel alloy system has found applications in the field of biomedical materials due to its excellent comprehensive performance. This review discusses the applications of Ti-based bulk metallic glasses in load-bearing implants such as bone plates and screws for long-term implantation. On the other hand, Mg-based metallic glasses, owing to their degradability, are primarily used in degradable bone nails, plates, and vascular stents. However, metallic glasses as biomaterials still face certain challenges. The Young’s modulus value of Ti-based metallic glasses is higher than that of human bones, leading to stress-shielding effects. Meanwhile, Mg-based metallic glasses degrade too quickly, resulting in the premature loss of mechanical properties and the formation of numerous bubbles, which hinder tissue healing. To address these issues, we propose the following development directions: (1) Introducing porous structures into titanium-based metallic glasses is an important research direction for reducing Young’s modulus; (2) To enhance the bioactivity of implant material surfaces, the surface modification of titanium-based metallic glasses is essential. (3) Developing antibacterial coatings and incorporating antibacterial metal elements into the alloys is essential to maintain the long-term effective antibacterial properties of metallic biomaterials. (4) Corrosion resistance must be further improved through the preparation of composite materials, while ensuring biocompatibility and safety, to achieve controllable degradation rates and degradation modes. Full article

(This article belongs to the Special Issue Liquid Metals: From Fundamentals to Applications)

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11 pages, 2511 KiB

Open AccessEditor’s ChoiceArticle

Parameters Tailoring on the Deposition of Hydroxyapatite by Pulsed Electrical Discharge

by Stefan Alexandru Laptoiu, Mihai Ovidiu Cojocaru, Marian Miculescu and Mihai Branzei

Materials 2024, 17(18), 4583; https://doi.org/10.3390/ma17184583 - 18 Sep 2024

Cited by 1 | Viewed by 782

Abstract

The creation of strong adhesive layers of hydroxyapatite-based bioceramics (with or without bioinert metals, such as Ta, Ag, and Ti) on biocompatible metallic supports enhances the local biofunctionalization of surfaces. The processing of electroconductive materials using electrical impulse discharges is versatile, enabling precise [...] Read more.

The creation of strong adhesive layers of hydroxyapatite-based bioceramics (with or without bioinert metals, such as Ta, Ag, and Ti) on biocompatible metallic supports enhances the local biofunctionalization of surfaces. The processing of electroconductive materials using electrical impulse discharges is versatile, enabling precise coating of selected areas with perfectly adherent layers of varying thicknesses. This study aims to quantify the effects of varying the electrical power from the source generating the impulse discharge and the specific processing time per unit area of the cathode (made of titanium alloy) on the relative mass increase of the cathode. The anode comprised a mixture of hydroxyapatite powder and a self-polymerizing electroconductive acrylic resin in a tantalum sheath. The effects of the parameter adjustments on single-layer deposition adherence were quantified using a central composite design to build a second-order orthogonal model. The most significant difference in relative mass was observed with a low-power source (5 W) ensuring the electrical discharge impulse, combined with the longest specified surface treatment time (17.5 s/cm² on a 4 cm² surface) for a single layer presenting the largest mass increase of 0.153% of the original mass. This study aimed to enhance the performance of medical implants by optimizing surface biofunctionalization through robust hydroxyapatite-based bioceramic adhesive layers on metallic supports, determining the optimal electrical power and processing time for cathode mass increase during deposition processes, and analyzing parameter adjustments using second-order statistical orthogonal central composite programming, with a focus on single-layer deposition to identify significant differences in relative mass under specific conditions. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))

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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 922

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 982

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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17 pages, 6700 KiB

Open AccessEditor’s ChoiceArticle

Detecting the Sigma Phase in Duplex Stainless Steel by Magnetic Noise and First Harmonic Analysis

by João Silva, Edgard Silva, Augusto Sampaio, Rayssa Lins, Josinaldo Leite, Victor Albuquerque Silva and João Manuel R. S. Tavares

Materials 2024, 17(18), 4561; https://doi.org/10.3390/ma17184561 - 17 Sep 2024

Viewed by 1055

Abstract

Non-destructive electromagnetic tests based on magnetic noise analysis have been developed to study, among others, residual stress, heat treatment outcomes, and harmful microstructures in terms of toughness. When subjected to thermal cycles above 550 °C, duplex stainless steels form an extremely hard and [...] Read more.

Non-destructive electromagnetic tests based on magnetic noise analysis have been developed to study, among others, residual stress, heat treatment outcomes, and harmful microstructures in terms of toughness. When subjected to thermal cycles above 550 °C, duplex stainless steels form an extremely hard and chromium-rich constituent that, if it is superior to 5%, compromises the steel’s corrosion resistance and toughness. In the present work, a study was carried out concerning the interaction of excitation waves with duplex stainless steel. Hence, by analyzing the magnetic noise and variations in the amplitude of the first harmonic of the excitation waves, the detection of the deleterious sigma phase in SAF 2205 steel is studied. To simplify the test, a Hall effect sensor replaced the pick-up coil placed on the opposite surface of the excitation coil. Sinusoidal excitation waves of 5 Hz and 25 Hz with amplitudes ranging from 0.25 V to 9 V were applied to samples with different amounts of the sigma phase, and the microstructures were characterized by scanning electron microscopy. The results show that the best testing condition consists of applying waves with amplitudes from 1 V to 2 V and using the first harmonic amplitude. Thus, the test proved effective for detecting the formation of the deleterious sigma phase and can follow the ability to absorb energy by impact and, thus, the material embrittlement. Full article

(This article belongs to the Special Issue Non-Destructive Testing of Materials and Parts: Techniques, Case Studies and Practical Applications)

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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 6 | Viewed by 2995

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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13 pages, 946 KiB

Open AccessEditor’s ChoiceArticle

Supercurrent and Superconducting Diode Effect in Parallel Double Quantum Dots with Rashba Spin–Orbit Interaction

by Feng Chi, Yaohong Shen, Yumei Gao, Jia Liu, Zhenguo Fu, Zichuan Yi and Liming Liu

Materials 2024, 17(18), 4497; https://doi.org/10.3390/ma17184497 - 13 Sep 2024

Viewed by 1211

Abstract

We study theoretically the supercurrent and the superconducting diode effect (SDE) in a structure comprising parallel-coupled double quantum dots (DQDs) sandwiched between two superconductor leads in the presence of a magnetic flux. The influence of the Rashba spin–orbit interaction (RSOI), which induces a [...] Read more.

We study theoretically the supercurrent and the superconducting diode effect (SDE) in a structure comprising parallel-coupled double quantum dots (DQDs) sandwiched between two superconductor leads in the presence of a magnetic flux. The influence of the Rashba spin–orbit interaction (RSOI), which induces a spin-dependent phase factor in the dot–superconductor coupling strength, is taken into account by adopting the nonequilibrium Green’s function technique. This RSOI-induced phase factor serves as a driving force for the supercurrent in addition to the usual superconducting phase difference, and it leads to the system’s left/right asymmetry. Correspondingly, the magnitude of the positive and negative critical currents become different from each other: the so-called SDE. Our results show that the period, magnitude, and direction of the supercurrents depend strongly on the RSOI-induced phase factor, dots’ energy levels, interdot coupling strengths, and the magnetic flux. In the absence of magnetic flux, the diode efficiency is negative and may approach

- 2

, which indicates the perfect diode effect with only negative flowing supercurrent in the absence of a positive one. Interestingly enough, both the sign and magnitude of the diode efficiency can be efficiently adjusted with the help of magnetic flux, the dots’ energy levels and the interdot coupling strength and thus provide a controllable SDE by rich means, such as gate voltage or host materials of the system. Full article

(This article belongs to the Special Issue Electronic, Optical and Magnetic Properties of Low-Dimensional Materials)

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12 pages, 550 KiB

Open AccessEditor’s ChoiceArticle

Crystal Structures and Piezoelectric Properties of Quenched and Slowly-Cooled BiFeO₃-BaTiO₃ Ceramics

by Su Hwan Go, Kang San Kim, Ye Rok Choi, Jeong-Seog Kim and Chae Il Cheon

Materials 2024, 17(18), 4492; https://doi.org/10.3390/ma17184492 - 13 Sep 2024

Viewed by 1084

Abstract

The BiFeO₃-BaTiO₃ (BF-BT) ceramics were here prepared through the solid-state reaction of Bi₂O₃, Fe₂O₃ and nano-sized BT powders. The crystal structures and piezoelectric properties were investigated in both quenched (AQ) and slowly cooled [...] Read more.

The BiFeO₃-BaTiO₃ (BF-BT) ceramics were here prepared through the solid-state reaction of Bi₂O₃, Fe₂O₃ and nano-sized BT powders. The crystal structures and piezoelectric properties were investigated in both quenched (AQ) and slowly cooled (SC) 0.7BF-0.3BT ceramics. Prior work has shown that rhombohedral and pseudo-cubic phases coexist in 0.7BF-0.3BT ceramics. In this work, the crystal structure of the pseudo-cubic phase was refined as a non-polar orthorhombic Pbnm phase in the SC sample and as a polar orthorhombic Pmc2₁ phase in the AQ sample. In addition to a sharp dielectric peak at about 620 °C, corresponding to the Curie temperature of the rhombohedral phase, a broad dielectric peak with strong frequency dispersion and a sharp frequency-independent dielectric peak were observed at around 500 °C in the SC and AQ samples, respectively. We determine that the dielectric anomalies around 500 °C were caused by a relaxor phase transition of the non-polar orthorhombic phase in the SC sample and a ferroelectric–paraelectric phase transition of the polar orthorhombic phase in the AQ sample. The AQ sample showed better ferroelectric and piezoelectric properties than the SC sample. The 0.7BF-0.3BT ceramic slowly cooled in a nitrogen atmosphere showed a well-saturated P-E curve and a similar temperature-dependent dielectric constant as the AQ sample. Our results indicate that large concentrations of oxygen vacancies produce a more distorted polar orthorhombic phase and better piezoelectric properties in the AQ sample than in the SC sample. Full article

(This article belongs to the Special Issue Design and Processing of Piezoelectric/Ferroelectric Ceramics)

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21 pages, 5094 KiB

Open AccessEditor’s ChoiceArticle

Parameter Optimization of a Surface Mechanical Rolling Treatment Process to Improve the Surface Integrity and Fatigue Property of FV520B Steel by Machine Learning

by Yongxin Zhou, Zheng Xing, Qianduo Zhuang, Jiao Sun and Xingrong Chu

Materials 2024, 17(18), 4505; https://doi.org/10.3390/ma17184505 - 13 Sep 2024

Cited by 3 | Viewed by 1681

Abstract

Surface integrity is a critical factor that affects the fatigue resistance of materials. A surface mechanical rolling treatment (SMRT) process can effectively improve the surface integrity of the material, thus enhancing the fatigue property. In this paper, an analysis of variance (ANOVA) and [...] Read more.

Surface integrity is a critical factor that affects the fatigue resistance of materials. A surface mechanical rolling treatment (SMRT) process can effectively improve the surface integrity of the material, thus enhancing the fatigue property. In this paper, an analysis of variance (ANOVA) and signal-to-noise ratio (SNR) are performed by orthogonal experimental design with SMRT parameters as variables and surface integrity indicators as optimization objectives, and the support vector machine-active learning (SVM-AL) model is proposed based on machine learning theory. The entire model includes three rounds of AL processes. In each round of the AL process, the SMRT parameters with relative average deviation and high output values from cross-validation are selected for the additional experimental supplement. The results show that the prediction accuracy and generalization ability of the SVM-AL model are significantly improved compared to the support vector machine (SVM) model. A fatigue test was also carried out, and the fatigue property of the SMRT specimens predicted by the SVM-AL model is also higher than that of the other specimens. Full article

(This article belongs to the Special Issue Mechanics, Fatigue and Fracture of Metallic Materials (Second Edition))

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17 pages, 12952 KiB

Open AccessEditor’s ChoiceArticle

Assessment of Changes in Selected Features of Pine and Birch Wood after Impregnation with Graphene Oxide

by Izabela Betlej, Sławomir Borysiak, Katarzyna Rybak, Barbara Nasiłowska, Aneta Bombalska, Zygmunt Mierczyk, Karolina Lipska, Piotr Borysiuk, Bogusław Andres, Małgorzata Nowacka and Piotr Boruszewski

Materials 2024, 17(18), 4464; https://doi.org/10.3390/ma17184464 - 11 Sep 2024

Cited by 1 | Viewed by 927

Abstract

In this work, pine and birch wood were modified by graphene oxide using a single vacuum impregnation method. The research results indicate that the impregnation of wood with graphene oxide increases the crystallinity of cellulose in both pine and birch wood, and the [...] Read more.

In this work, pine and birch wood were modified by graphene oxide using a single vacuum impregnation method. The research results indicate that the impregnation of wood with graphene oxide increases the crystallinity of cellulose in both pine and birch wood, and the increase in crystallinity observed in the case of birch was more significant than in the case of pine. FT-IR analyses of pine samples impregnated with graphene oxide showed changes in intensity in the absorption bands of 400–600, 700–1500 cm⁻¹, and 3200–3500 cm⁻¹ and a peak separation of 1102 cm⁻¹, which may indicate new C-O-C connections. In the case of birch, only some differences were noticed related to the vibrations of the OH group. The proposed modification also affects changes in the color of the wood surface, with earlywood containing more graphene oxide than latewood. Analysis of scanning electron microscope images revealed that graphene oxide adheres flat to the cell wall. Considering the differences in the anatomical structure of both wood species, the research showed a statistically significant difference in water absorption and retention of graphene oxide in wood cells. Graphene oxide does not block the flow of water in the wood, as evidenced by the absorbability of the working liquid at the level of 580–602 kg/m³, which corresponds to the value of pure water absorption by wood in the impregnation method using a single negative pressure. In this case, higher graphene oxide retention values were obtained for pine wood. Full article

(This article belongs to the Section Advanced Materials Characterization)

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17 pages, 23305 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

In Situ Investigation of Tensile Response for Inconel 718 Micro-Architected Materials Fabricated by Selective Laser Melting

by Ioannis Filippos Kyriakidis, Nikolaos Kladovasilakis, Eleftheria Maria Pechlivani, Apostolos Korlos, Constantine David and Konstantinos Tsongas

Materials 2024, 17(17), 4433; https://doi.org/10.3390/ma17174433 - 9 Sep 2024

Cited by 2 | Viewed by 1342

Abstract

Topology optimization enables the design of advanced architected materials with tailored mechanical properties and optimal material distribution. This method can result in the production of parts with uniform mechanical properties, reducing anisotropy effects and addressing a critical challenge in metal additive manufacturing (AM). [...] Read more.

Topology optimization enables the design of advanced architected materials with tailored mechanical properties and optimal material distribution. This method can result in the production of parts with uniform mechanical properties, reducing anisotropy effects and addressing a critical challenge in metal additive manufacturing (AM). The current study aims to examine the micro-tensile response of Inconel 718 architected materials utilizing the Selective Laser Melting Technique. In this context, three novel architected materials, i.e., Octet, Schwarz Diamond (SD), and hybrid Schwarz Diamond and Face Centered Cubic (FCC), were tested in three different relative densities. The specimens were then subjected to uniaxial quasi-static tensile tests to determine their key mechanical properties, including elastic modulus, yield strength, and ultimate tensile strength (UTS), as well as the scaling laws describing the tensile response of each architected material. In situ Scanning Electron Microscopy (SEM) has been performed to observe the structure and grain morphology of the 3D printed specimens along with the phase transitions (elastic, plastic), the crack propagation, and the overall failure mechanisms. The results highlight the effect of the lattice type and the relative density on the mechanical properties of architected materials. Topologically optimized structures presented a 70–80% reduction in overall strength, while the SD and SD&FCC structures presented higher stretching dominated behavior, which was also verified by the n-value range (1–2) extracted from the identification of the scaling laws. Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Metal and Non-Metallic Materials)

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13 pages, 7271 KiB

Open AccessEditor’s ChoiceArticle

In Situ Analysis of Binder Degradation during Catalyst-Accelerated Stress Test of Polymer Electrolyte Membrane Fuel Cells

by Donggeun Yoo, Sujung Park, Sohyeong Oh, Minsoo P. Kim and Kwonpil Park

Materials 2024, 17(17), 4425; https://doi.org/10.3390/ma17174425 - 9 Sep 2024

Cited by 3 | Viewed by 1361

Abstract

High-oxygen-permeability ionomers (HOPIs) are being actively developed to enhance the performance and durability of high-power polymer electrolyte membrane fuel cells (PEMFCs). While methods for evaluating binder performance are well-established, techniques for assessing binder durability and measuring its degradation in situ during the AST [...] Read more.

High-oxygen-permeability ionomers (HOPIs) are being actively developed to enhance the performance and durability of high-power polymer electrolyte membrane fuel cells (PEMFCs). While methods for evaluating binder performance are well-established, techniques for assessing binder durability and measuring its degradation in situ during the AST process remain limited. This study examines the distribution of relaxation times (DRT) and Warburg-like response (WLR) methods as in situ analysis techniques during the catalyst-accelerated stress test (AST) process. We conducted catalyst-ASTs (0.6–0.95 V cycling) for 20,000 cycles, monitoring changes using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). Contrary to expectations, during the catalyst-AST, the ion transport resistance of the binder decreased, indicating no binder degradation. Scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) analysis revealed that the degradation rate of the catalyst and the support was relatively higher than that of the binder, leading to a reduction in catalyst layer thickness and improved binder network formation. By applying the DRT method during the catalyst-AST process, we were able to measure the increase in oxygen reduction reaction (ORR) resistance and the decrease in proton transport resistance in situ. This allowed for the real-time detection of the reduction in catalyst layer thickness and improvements in ionomer networks due to catalyst and support degradation. These findings provide new insights into the complex interplay between catalyst degradation and binder performance, contributing to the development of more durable PEMFC components. Full article

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

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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 993

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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25 pages, 14228 KiB

Open AccessEditor’s ChoiceReview

A Review on Metallurgical Issues in the Production and Welding Processes of Clad Steels

by Fabio Giudice, Severino Missori, Cristina Scolaro and Andrea Sili

Materials 2024, 17(17), 4420; https://doi.org/10.3390/ma17174420 - 8 Sep 2024

Cited by 6 | Viewed by 1988

Abstract

Carbon and low-alloy steel plates clad with stainless steel or other metals are a good choice to meet the demand for cost-effective materials to be used in many corrosive environments. Numerous technical solutions are developed for the production of clad steel plates, as [...] Read more.

Carbon and low-alloy steel plates clad with stainless steel or other metals are a good choice to meet the demand for cost-effective materials to be used in many corrosive environments. Numerous technical solutions are developed for the production of clad steel plates, as well as for their joining by fusion welding. For thick plates, a careful strategy is required in carrying out the multiple passes and in choosing the most suitable filler metals, having to take into account the composition of the base metal and the cladding layer. The specificity of the different processes and materials involved requires an adequate approach in the study of the metallurgical characteristics of clad steel, thus arousing the interest of researchers. Focusing mainly on ferritic steel plates clad with austenitic steel, this article aims to review the scientific literature of recent years which deals with both the production and the fusion welding processes. The metallurgical issues concerning the interfaces and the effects of microstructural characteristics on mechanical behaviour and corrosion resistance will be addressed; in particular, the effects on the fusion and thermally affected zones that form during the fusion welding and weld overlay processes will be analysed and discussed. Full article

(This article belongs to the Special Issue New Perspectives in Welding and Joining Processes of Metallic Materials)

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13 pages, 1547 KiB

Open AccessEditor’s ChoiceArticle

Predicting Yield Strength and Plastic Elongation in Body-Centered Cubic High-Entropy Alloys

by Diego Ibarra Hoyos, Quentin Simmons and Joseph Poon

Materials 2024, 17(17), 4422; https://doi.org/10.3390/ma17174422 - 8 Sep 2024

Viewed by 1820

Abstract

We employ machine learning (ML) to predict the yield stress and plastic strain of body-centered cubic (BCC) high-entropy alloys (HEAs) in the compression test. Our machine learning model leverages currently available databases of BCC and BCC+B2 entropy alloys, using feature engineering to capture [...] Read more.

We employ machine learning (ML) to predict the yield stress and plastic strain of body-centered cubic (BCC) high-entropy alloys (HEAs) in the compression test. Our machine learning model leverages currently available databases of BCC and BCC+B2 entropy alloys, using feature engineering to capture electronic factors, atomic ordering from mixing enthalpy, and the D parameter related to stacking fault energy. The model achieves low Root Mean Square Errors (RMSE). Utilizing Random Forest Regression (RFR) and Genetic Algorithms for feature selection, our model excels in both predictive accuracy and interpretability. Rigorous 10-fold cross-validation ensures robust generalization. Our discussion delves into feature importance, highlighting key predictors and their impact on mechanical properties. This work provides an important step toward designing high-performance structural high-entropy alloys, providing a powerful tool for predicting mechanical properties and identifying new alloys with superior strength and ductility. Full article

(This article belongs to the Special Issue Advances in High Entropy Alloys and High Entropy Carbides: Microstructural and Mechanical Properties and Modeling)

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13 pages, 4081 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Raman Scattering in CVD-Grown MoS₂/Ag Nanoparticle Hybrids

by Dionysios M. Maratos, Antonios Michail, Alkeos Stamatelatos, Spyridon Grammatikopoulos, Dimitris Anestopoulos, Vassilis Tangoulis, Konstantinos Papagelis, John Parthenios and Panagiotis Poulopoulos

Materials 2024, 17(17), 4396; https://doi.org/10.3390/ma17174396 - 6 Sep 2024

Cited by 2 | Viewed by 1714

Abstract

Surface-Enhanced Raman Spectroscopy (SERS) is a powerful, non-destructive technique for enhancing molecular spectra, first discovered in 1974. This study investigates the enhancement of Raman signals from single- and few-layer molybdenum disulfide (MoS₂) when interacting with silver nanoparticles. We synthesized a MoS [...] Read more.

Surface-Enhanced Raman Spectroscopy (SERS) is a powerful, non-destructive technique for enhancing molecular spectra, first discovered in 1974. This study investigates the enhancement of Raman signals from single- and few-layer molybdenum disulfide (MoS₂) when interacting with silver nanoparticles. We synthesized a MoS₂ membrane primarily consisting of monolayers and bilayers through a wet chemical vapor deposition method using metal salts. The silver nanoparticles were either directly grown on the MoS₂ membrane or placed beneath it. Raman measurements revealed a significant increase in signal intensity from the MoS₂ membrane on the silver nanoparticles, attributed to localized surface plasmon resonances that facilitate SERS. Our results indicate that dichalcogenide/plasmonic systems have promising applications in the semiconductor industry. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

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13 pages, 10499 KiB

Open AccessEditor’s ChoiceArticle

High Milling Time Influence on the Phase Stability and Electrical Properties of Fe₅₀Mn₃₅Sn₁₅ Heusler Alloy Obtained by Mechanical Alloying

by Florin Popa, Traian Florin Marinca, Niculina Argentina Sechel, Dan Ioan Frunză and Ionel Chicinaș

Materials 2024, 17(17), 4355; https://doi.org/10.3390/ma17174355 - 3 Sep 2024

Viewed by 749

Abstract

Fe₅₀Mn₃₅Sn₁₅ Heusler alloy, obtained by mechanical alloying, was subjected to larger milling times in the range of 30–50 h to study the phase stability and morphology. X-ray diffraction studies have shown that the milled samples crystallise in a [...] Read more.

Fe₅₀Mn₃₅Sn₁₅ Heusler alloy, obtained by mechanical alloying, was subjected to larger milling times in the range of 30–50 h to study the phase stability and morphology. X-ray diffraction studies have shown that the milled samples crystallise in a disordered A₂ structure. The A₂ structure was found to be stable in the milling range studied, contrary to the computation studies performed on this composition. Using Rietveld refinements, the lattice parameter, mean crystallite size, and lattice strain were computed. The nature of the obtained phases by milling was found to be nanocrystalline with values below 50 nm. A linear increase rate of 0.00713 (h⁻¹) was computed for lattice strain as the milling time increased. As the milling time increases, the lattice parameter of the cubic Heusler was found to have a decreasing behaviour, reaching 2.9517 Å at 50 h of milling. The morphological and elemental distribution—characterised by scanning electron microscopy and energy-dispersive X-ray spectroscopy—evidenced Mn and Sn phase clustering. As the milling time increased, the morphology of the sample was found to change. The Mn and Sn cluster size was quantified by elemental line profile. Electrical resistivity evolution with milling time was analysed, showing a peak for 40 h of milling time. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))

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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 2 | Viewed by 1072

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

Cited by 1 | Viewed by 1545

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 771

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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13 pages, 17420 KiB

Open AccessEditor’s ChoiceArticle

Electrospun Polymeric Fiber Systems Inoculated with Cyanoacrylate Tissue Adhesive: A Novel Hemostatic Alternative during Open Surgery

by Victor P. Tosa, Alexandru Ilie-Ene, Septimiu C. Tripon, Amalia Mesaros, Radu Fechete, Nicoleta Tosa, Alexandra Csapai, George C. Dindelegan and Catalin O. Popa

Materials 2024, 17(17), 4318; https://doi.org/10.3390/ma17174318 - 30 Aug 2024

Cited by 2 | Viewed by 1246

Abstract

Natural-based and synthetic tissue adhesives have attracted extensive attention in the last two decades for their ability to stabilize uncontrolled bleeding instances. However; these materials present several drawbacks during use that scientists have tried to minimize in order to optimize their usage. This [...] Read more.

Natural-based and synthetic tissue adhesives have attracted extensive attention in the last two decades for their ability to stabilize uncontrolled bleeding instances. However; these materials present several drawbacks during use that scientists have tried to minimize in order to optimize their usage. This study comprises the development of a novel wound dressing, combining the excellent properties of polylactic acid (PLA) non-woven textile, as substrate, obtained through electrospinning, and a cyanoacrylate-based (CA) tissue adhesive, for rapid hemostatic action. Thus, the fabrication of electrospun PLA membranes at three different PLA concentrations, the design and manufacturing of the support system and the production of surgical patches were carried out. SEM and FT-IR methods were employed for analyzing the morphology as well as the indicative markers for the shelf life evolution of the obtained patches. PLA fibers with well-defined structures and a mean diameter varying between 4.6 and 7.24 μm were obtained with the increase of the concentration of the PLA solutions. In vivo tests on a rat model as well as peeling tests for good patch adhesion on liver fragments harvested from the test animals, with a limit for the strength of the liver tissue of 1.5 N, were carried out. The devices exhibited excellent adhesion to the parenchymal tissue and a long enough shelf life to be used with success in surgical procedures, also facilitating prompt hemostatic action. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))

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16 pages, 11171 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of Macro- and Micro-Geometry of Models Made of Photopolymer Resins Using the PolyJet Method

by Paweł Turek, Anna Bazan, Grzegorz Budzik, Tomasz Dziubek and Łukasz Przeszłowski

Materials 2024, 17(17), 4315; https://doi.org/10.3390/ma17174315 - 30 Aug 2024

Cited by 1 | Viewed by 1073

Abstract

Additive manufacturing (AM) techniques are among the fastest-growing technologies for producing even the most geometrically complex models. Unfortunately, the lack of development of metrology guidelines for these methods, related to dimensional and geometry accuracy and surface roughness, significantly limits the commercialization of finished [...] Read more.

Additive manufacturing (AM) techniques are among the fastest-growing technologies for producing even the most geometrically complex models. Unfortunately, the lack of development of metrology guidelines for these methods, related to dimensional and geometry accuracy and surface roughness, significantly limits the commercialization of finished products manufactured using these methods. This paper aims to evaluate the macro- and micro-geometry of models manufactured using the PolyJet method from three types of photopolymer resins: Digital ABS Plus, RGD 720, and Vero Clear. For this purpose, test parts were designed and then manufactured on an Object 350 Connex3 3D printer. The Atos II Triple Scan optical system and the InfiniteFocusG4 microscope were used to evaluate macro- and micro-geometry, respectively. For both systems, measurement procedures were developed to obtain statistical results for evaluating geometric accuracy and surface roughness parameters. In the case of macro-geometry, for Digital ABS Plus and Vero Clear materials, 50% of the central deviations (between first quartile Q1 and third quartile Q3) lie within the range (−0.06, 0.03 mm) and for RGD 720 material within the range (−0.08, 0.01 mm). For micro-geometry, the arithmetic mean height (Sa) values for the Digital ABS Plus and Vero Clear samples were approximately 1.6 and 2.0 µm, respectively, while for RGD 720, it was 15.9 µm. The total roughness height expressed by reduced peak height (Spk) + core height (Sk) + reduced dale depth (Svk) for the Digital ABS Plus and Vero Clear samples was approximately 9.1 and 10.5 µm, respectively, while for the RGD 720, it was 101.9 µm. Full article

(This article belongs to the Special Issue Material Surface Topography Measurement, Analysis and Characterization)

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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 3 | Viewed by 4015

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 1173

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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23 pages, 4717 KiB

Open AccessEditor’s ChoiceReview

Polysaccharide-Based Composite Systems in Bone Tissue Engineering: A Review

by Karina Niziołek, Dagmara Słota and Agnieszka Sobczak-Kupiec

Materials 2024, 17(17), 4220; https://doi.org/10.3390/ma17174220 - 27 Aug 2024

Cited by 5 | Viewed by 2327

Abstract

In recent years, a growing demand for biomaterials has been observed, particularly for applications in bone regenerative medicine. Bone tissue engineering (BTE) aims to develop innovative materials and strategies for repairing and regenerating bone defects and injuries. Polysaccharides, due to their biocompatibility, biodegradability [...] Read more.

In recent years, a growing demand for biomaterials has been observed, particularly for applications in bone regenerative medicine. Bone tissue engineering (BTE) aims to develop innovative materials and strategies for repairing and regenerating bone defects and injuries. Polysaccharides, due to their biocompatibility, biodegradability as well as bioactivity, have emerged as promising candidates for scaffolds or composite systems in BTE. Polymers combined with bioactive ceramics can support osteointegration. Calcium phosphate (CaP) ceramics can be a broad choice as an inorganic phase that stimulates the formation of new apatite layers. This review provides a comprehensive analysis of composite systems based on selected polysaccharides used in bone tissue engineering, highlighting their synthesis, properties and applications. Moreover, the applicability of the produced biocomposites has been analyzed, as well as new trends in modifying biomaterials and endowing them with new functionalizations. The effects of these composites on the mechanical properties, biocompatibility and osteoconductivity were critically analyzed. This article summarizes the latest manufacturing methods as well as new developments in polysaccharide-based biomaterials for bone and cartilage regeneration applications. Full article

(This article belongs to the Special Issue Bone Tissue Engineering Materials: From Preparation to Properties)

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12 pages, 3635 KiB

Open AccessEditor’s ChoiceArticle

Finite Element Analysis of the Structure and Working Principle of Solid-State Shear Milling (S3M) Equipment

by Lingfei Wei, Chao Wang, Ruoxuan Duan, Zehang Zhou and Canhui Lu

Materials 2024, 17(17), 4210; https://doi.org/10.3390/ma17174210 - 26 Aug 2024

Cited by 1 | Viewed by 969

Abstract

Solid-state shear milling (S3M) equipment is an evolution from traditional stone mills, enabling the processing of polymer materials and fillers through crushing, mixing, and mechanochemical reactions at ambient temperature. Due to the complex structure of the mill-pan, empirical data alone are insufficient to [...] Read more.

Solid-state shear milling (S3M) equipment is an evolution from traditional stone mills, enabling the processing of polymer materials and fillers through crushing, mixing, and mechanochemical reactions at ambient temperature. Due to the complex structure of the mill-pan, empirical data alone are insufficient to give a comprehensive understanding of the physicochemical interactions during the milling process. To provide an in-depth insight of the working effect and mechanism of S3M equipment, finite element method (FEM) analysis is employed to simulate the milling dynamics, which substantiates the correlation between numerical outcomes and experimental observations. A model simplification strategy is proposed to optimize calculation time without compromising accuracy. The findings in this work demonstrate the S-S bond breakage mechanism behind stress-induced devulcanization and suggest the structural optimizations for enhancing the devulcanization and pulverization efficiency of S3M equipment, thereby providing a theoretical foundation for its application in material processing. Full article

(This article belongs to the Special Issue Advances in Bio-Polymer and Polymer Composites)

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15 pages, 8923 KiB

Open AccessEditor’s ChoiceArticle

Bio-Inspired Curved-Elliptical Lattice Structures for Enhanced Mechanical Performance and Deformation Stability

by Zhengmiao Guo, Fan Yang, Lingbo Li and Jiacheng Wu

Materials 2024, 17(17), 4191; https://doi.org/10.3390/ma17174191 - 24 Aug 2024

Viewed by 2053

Abstract

Lattice structures, characterized by their lightweight nature, high specific mechanical properties, and high design flexibility, have found widespread applications in fields such as aerospace and automotive engineering. However, the lightweight design of lattice structures often presents a trade-off between strength and stiffness. To [...] Read more.

Lattice structures, characterized by their lightweight nature, high specific mechanical properties, and high design flexibility, have found widespread applications in fields such as aerospace and automotive engineering. However, the lightweight design of lattice structures often presents a trade-off between strength and stiffness. To tackle this issue, a bio-inspired curved-elliptical (BCE) lattice is proposed to enhance the mechanical performance and deformation stability of three-dimensional lattice structures. BCE lattice specimens with different parameters were fabricated using selective laser melting (SLM) technology, followed by quasi-static compression tests. Finite element (FE) numerical simulations were also carried out for validation. The results demonstrate that the proposed BCE lattice structures exhibit stronger mechanical performance and more stable deformation modes that can be adjusted through parameter tuning. Specifically, by adjusting the design parameters, the BCE lattice structure can exhibit a bending-dominated delocalized deformation mode, avoiding catastrophic collapse during deformation. The specific energy absorption (SEA) can reach 24.6 J/g at a relative density of only 8%, with enhancements of 48.5% and 297.6% compared with the traditional energy-absorbing lattices Octet and body-center cubic (BCC), respectively. Moreover, the crushing force efficiency (CFE) of the BCE lattice structure surpasses those of Octet and BCC by 34.9% and 15.8%, respectively. Through a parametric study of the influence of the number of peaks N and the curve amplitude A on the compression performance of the BCE lattice structure, the compression deformation mechanism is further analyzed. The results indicate that the curve amplitude A and the number of peaks N have significant impacts on the deformation mode of the BCE lattice. By adjusting the parameters N and A, a structure with a combination of high energy absorption, high stiffness, and strong fracture resistance can be obtained, integrating the advantages of tensile-dominated and bending-dominated lattice structures. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Structures: Process and Applications)

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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 964

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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19 pages, 2385 KiB

Open AccessEditor’s ChoiceArticle

Characterization and Modeling of Out-of-Plane Behavior of Fiber-Based Materials: Numerical Illustration of Wrinkle in Deep Drawing

by Cedric W. Sanjon, Yuchen Leng, Yi Yan, Peter Groche, Marek Hauptmann, Nicole Ludat and Jens-Peter Majschak

Materials 2024, 17(17), 4177; https://doi.org/10.3390/ma17174177 - 23 Aug 2024

Viewed by 835

Abstract

The characterization and modeling of the out-of-plane behavior of fiber-based materials is essential for understanding their mechanical properties and improving their performance in various applications, especially in the forming process. Despite this, research on paper and paperboard has mainly focused on its in-plane [...] Read more.

The characterization and modeling of the out-of-plane behavior of fiber-based materials is essential for understanding their mechanical properties and improving their performance in various applications, especially in the forming process. Despite this, research on paper and paperboard has mainly focused on its in-plane behavior rather than its out-of-plane behavior. However, for accurate material characterization and modeling, it is critical to consider the out-of-plane behavior. In particular, delamination occurs during forming processes such as creasing, folding, and deep drawing. In this study, three material models for paperboard are presented: a single all-material continuum model and two composite models using different cohesion methods. The two composite models decouple in-plane and out-of-plane behavior and consist of continuum models describing the behavior of individual layers and cohesive interface models connecting the layers. Material characterization experiments are performed to derive the model parameters and verify the models. The models are validated using three-point bending and bulge tests and show good agreement. A case study is also conducted on the application of the three models in the simulation of a deep drawing process with respect to wrinkle formation. By comparing the simulation results of wrinkle formation in the deep drawing process, the composite models, especially the cohesive interface composite model, show greater accuracy in replicating the experimental results, indicating that a single continuum model can also be used to represent wrinkles. Full article

(This article belongs to the Section Materials Simulation and Design)

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11 pages, 4618 KiB

Open AccessEditor’s ChoiceArticle

Modeling Study of Si₃N₄ Waveguides on a Sapphire Platform for Photonic Integration Applications

by Diandian Zhang, Shui-Qing Yu, Gregory J. Salamo, Richard A. Soref and Wei Du

Materials 2024, 17(16), 4148; https://doi.org/10.3390/ma17164148 - 22 Aug 2024

Cited by 9 | Viewed by 1830

Abstract

Sapphire has various applications in photonics due to its broadband transparency, high-contrast index, and chemical and physical stability. Photonics integration on the sapphire platform has been proposed, along with potentially high-performance lasers made of group III–V materials. In parallel with developing active devices [...] Read more.

Sapphire has various applications in photonics due to its broadband transparency, high-contrast index, and chemical and physical stability. Photonics integration on the sapphire platform has been proposed, along with potentially high-performance lasers made of group III–V materials. In parallel with developing active devices for photonics integration applications, in this work, silicon nitride optical waveguides on a sapphire substrate were analyzed using the commercial software Comsol Multiphysics in a spectral window of 800~2400 nm, covering the operating wavelengths of III–V lasers, which could be monolithically or hybridly integrated on the same substrate. A high confinement factor of ~90% near the single-mode limit was obtained, and a low bending loss of ~0.01 dB was effectively achieved with the bending radius reaching 90 μm, 70 μm, and 40 μm for wavelengths of 2000 nm, 1550 nm, and 850 nm, respectively. Furthermore, the use of a pedestal structure or a SiO₂ bottom cladding layer has shown potential to further reduce bending losses. The introduction of a SiO₂ bottom cladding layer effectively eliminates the influence of the substrate’s larger refractive index, resulting in further improvement in waveguide performance. The platform enables tightly built waveguides and small bending radii with high field confinement and low propagation losses, showcasing silicon nitride waveguides on sapphire as promising passive components for the development of high-performance and cost-effective PICs. Full article

(This article belongs to the Special Issue Thin Films, Nanostructures and Devices for Optoelectronics Applications)

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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 3 | Viewed by 1492

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

Cited by 1 | Viewed by 1557

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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18 pages, 10491 KiB

Open AccessEditor’s ChoiceArticle

In Situ Synthesis of (Mo,Cr)Si₂ Composites by Spark Plasma Sintering

by Yue-Yao Wang and Guo-Hua Zhang

Materials 2024, 17(16), 4105; https://doi.org/10.3390/ma17164105 - 19 Aug 2024

Cited by 1 | Viewed by 1000

Abstract

This research investigated the impact of Cr content on the properties of (Mo,Cr)Si₂ composites. Composites with CrSi₂ molar fractions ranging from 0% to 10% were fabricated using spark plasma sintering (SPS). The study undertook a systematic analysis of the surface morphology, [...] Read more.

This research investigated the impact of Cr content on the properties of (Mo,Cr)Si₂ composites. Composites with CrSi₂ molar fractions ranging from 0% to 10% were fabricated using spark plasma sintering (SPS). The study undertook a systematic analysis of the surface morphology, phase composition, mechanical properties, and high-temperature oxidation resistance of the sintered samples across different compositions. Notably, the (Mo₉₅,Cr₅)Si₂ composite sintered at 1400 °C exhibited enhanced properties, including a Vickers hardness of 11.6 GPa, a fracture toughness of 4.6 MPa·m^1/2, and a flexural strength of 397 MPa. Upon oxidation at 1500 °C, the (Mo,Cr)Si₂ composites formed a protective oxide layer comprised of SiO₂ and Cr₂O₃. It was found that the generation and thickening of the protective oxide layer was promoted by the addition of moderate amounts of Cr to MoSi₂. Full article

(This article belongs to the Special Issue Sintering of Ceramic Materials)

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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

Cited by 2 | Viewed by 1089

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

Cited by 1 | Viewed by 1001

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 991

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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11 pages, 3441 KiB

Open AccessEditor’s ChoiceArticle

Enhancing Energy Storage Performance of 0.85Bi_0.5Na_0.5TiO₃-0.15LaFeO₃ Lead-Free Ferroelectric Ceramics via Buried Sintering

by Yixiao Zhang, Yuchen Jia, Jian Yang, Zixuan Feng, Shuohan Sun, Xiaolong Zhu, Haotian Wang, Shiguang Yan and Ming Zheng

Materials 2024, 17(16), 4019; https://doi.org/10.3390/ma17164019 - 13 Aug 2024

Cited by 3 | Viewed by 1352

Abstract

Bismuth sodium titanate (Bi_0.5Na_0.5TiO₃, BNT) ceramics are expected to replace traditional lead-based materials because of their excellent ferroelectric and piezoelectric characteristics, and they are widely used in the industrial, military, and medical fields. However, BNT ceramics have [...] Read more.

Bismuth sodium titanate (Bi_0.5Na_0.5TiO₃, BNT) ceramics are expected to replace traditional lead-based materials because of their excellent ferroelectric and piezoelectric characteristics, and they are widely used in the industrial, military, and medical fields. However, BNT ceramics have a low breakdown field strength, which leads to unsatisfactory energy storage performance. In this work, 0.85Bi_0.5Na_0.5TiO₃-0.15LaFeO₃ ceramics are prepared by the traditional high-temperature solid-phase reaction method, and their energy storage performance is greatly enhanced by improving the process of buried sintering. The results show that the buried sintering method can inhibit the formation of oxygen vacancy, reduce the volatilization of Bi₂O₃, and greatly improve the breakdown field strength of the ceramics so that the energy storage performance can be significantly enhanced. The breakdown field strength increases from 210 kV/cm to 310 kV/cm, and the energy storage density increases from 1.759 J/cm³ to 4.923 J/cm³. In addition, the energy storage density and energy storage efficiency of these ceramics have good frequency stability and temperature stability. In this study, the excellent energy storage performance of the ceramics prepared by the buried sintering method provides an effective idea for the design of lead-free ferroelectric ceramics with high energy storage performance and greatly expands its application field. Full article

(This article belongs to the Special Issue Ferroelectric, Magnetic, and Multiferroic Materials and Applications)

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11 pages, 2224 KiB

Open AccessEditor’s ChoiceArticle

Color Stability of Various Orthodontic Clear Aligner Systems after Submersion in Different Staining Beverages

by Nicolae Daniel Olteanu, Ionut Taraboanta, Tinela Panaite, Carina Balcos, Sorana Nicoleta Rosu, Raluca Maria Vieriu, Stefania Dinu and Irina Nicoleta Zetu

Materials 2024, 17(16), 4009; https://doi.org/10.3390/ma17164009 - 12 Aug 2024

Cited by 4 | Viewed by 2379

Abstract

This study aimed to compare the color changes in two different orthodontic clear aligner systems after submersion in various beverages for 14 days. The tested aligner systems were Taglus Premium made of polyethylene terephthalate glycol (the TAG group) and CA^® Prodin+ made [...] Read more.

This study aimed to compare the color changes in two different orthodontic clear aligner systems after submersion in various beverages for 14 days. The tested aligner systems were Taglus Premium made of polyethylene terephthalate glycol (the TAG group) and CA^® Prodin+ made of a transparent copolyester and a thermoplastic elastomer (the PRO group). A total of 56 samples were firstly divided into two groups according to the tested system—TAG and PRO. Each group was subsequently divided in four subgroups according to immersion solution: A—artificial saliva, B—cola, C—coffee, D—red wine. Color measurements were performed on Days 1, 7 and 14 using a portable colorimeter and the CIE L*a*b* system. The obtained results showed significant color changes in both materials when exposed to coffee and red wine (p > 0.05). Samples in the PRO group showed a greater susceptibility to discoloration (higher ΔE values) when compared to the TAG group after submersion in cola (p = 0.025), coffee (p = 0.005) and red wine (p = 0.041) solutions. Statistical analysis revealed that all of the color parameters ΔL*, Δa*, Δb* and ΔE of both tested materials were affected by submersion in coffee solution for 14 days. In conclusion, the CA^® Pro+ aligner system is more prone to staining compared to the Taglus material after submersion for 14 days in cola, coffee and red wine solutions. Submersion for 14 days in coffee solution alters all of the color parameters (ΔL, Δa, Δb and ΔE) of both tested aligner materials. Full article

(This article belongs to the Special Issue Advanced Dental Materials: From Design to Application)

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29 pages, 16855 KiB

Open AccessEditor’s ChoiceArticle

Crashworthiness Performance and Multi-Objective Optimization of Bi-Directional Corrugated Tubes under Quasi-Static Axial Crushing

by Liuxiao Zou, Xin Wang, Ruojun Wang, Xin Huang, Menglei Li, Shuai Li, Zengyan Jiang and Weilong Yin

Materials 2024, 17(16), 3958; https://doi.org/10.3390/ma17163958 - 9 Aug 2024

Viewed by 1496

Abstract

Longitudinal corrugated tubes (LCTs) exhibit stable platform force under axial compression but have low specific energy absorption. Conversely, circumferential corrugated tubes (CCTs) offer higher specific energy absorption but with unstable platform force. To overcome these limitations, this paper introduces a novel bi-directional corrugated [...] Read more.

Longitudinal corrugated tubes (LCTs) exhibit stable platform force under axial compression but have low specific energy absorption. Conversely, circumferential corrugated tubes (CCTs) offer higher specific energy absorption but with unstable platform force. To overcome these limitations, this paper introduces a novel bi-directional corrugated tube (BCT) that amalgamates the strengths of both the CCT and LCT while mitigating their weaknesses. The BCT is formed by rolling a bi-directional corrugated structure into a circular tubular form. Numerical simulations of the BCT closely align with experimental results. The study further examines the influence of discrete parameters on the BCT’s performance through simulations and identifies the tube’s optimal design using the integral entropy TOPSIS method. A full factorial experimental approach is then employed to investigate the impact of radial amplitude, axial amplitude, and neutral surface diameter on the crushing behavior of the BCT, comparing it with the CCT and LCT. The results reveal that increasing

A_{i}

enhances the axial resistance of the structure, while increasing

A_{j}

reduces the buckling effect, resulting in a higher specific energy absorption and lower ultimate load capacity for the BCT compared to the CCT and LCT. A simultaneous multi-objective optimization of the CCT, LCT, and BCT confirms that the BCT offers superior specific energy absorption and ultimate load capacity. The optimal configuration parameters for the BCT have been determined, providing significant insights for practical applications in crashworthiness engineering. Full article

(This article belongs to the Special Issue Advances in Modelling and Simulation of Materials in Applied Sciences)

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30 pages, 3102 KiB

Open AccessEditor’s ChoiceReview

Current Progress in Research into Environmentally Friendly Rigid Polyurethane Foams

by Sylwia Makowska, Dawid Szymborski, Natalia Sienkiewicz and Agnė Kairytė

Materials 2024, 17(16), 3971; https://doi.org/10.3390/ma17163971 - 9 Aug 2024

Cited by 3 | Viewed by 2749

Abstract

Polyurethane foams are materials characterized by low density and thermal conductivity and can therefore be used as thermal insulation materials. They are synthesized from toxic and environmentally unfriendly petrochemicals called isocyanates and polyols, which react with each other to form a urethane group [...] Read more.

Polyurethane foams are materials characterized by low density and thermal conductivity and can therefore be used as thermal insulation materials. They are synthesized from toxic and environmentally unfriendly petrochemicals called isocyanates and polyols, which react with each other to form a urethane group via the displacement of the movable hydrogen atom of the −OH group of the alcohol to the nitrogen atom of the isocyanate group. The following work describes the synthesis of polyurethane foams, focusing on using environmentally friendly materials, such as polyols derived from plant sources or modifiers, to strengthen the foam interface derived from plant precipitation containing cellulose derived from paper waste. The polyurethane foam industry is looking for new sources of materials to replace the currently used petrochemical products. The solutions described are proving to be an innovative and promising area capable of changing the face of current PU foam synthesis. Full article

(This article belongs to the Special Issue Polymers, Processing and Sustainability)

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23 pages, 5371 KiB

Open AccessEditor’s ChoiceArticle

Low-Cycle Fatigue Properties of Bimetallic Steel Bar with Buckling: Energy-Based Numerical and Experimental Investigations

by Xuanyi Xue, Fei Wang, Neng Wang, Jianmin Hua and Wenjie Deng

Materials 2024, 17(16), 3974; https://doi.org/10.3390/ma17163974 - 9 Aug 2024

Cited by 2 | Viewed by 960

Abstract

A bimetallic steel bar (BSB) consisting of stainless-steel cladding and carbon steel substrate exhibits excellent corrosion resistance and good mechanical properties. The bimetallic structure of BSBs may affect their low-cycle fatigue performance, and current investigations on the above issue are limited. In this [...] Read more.

A bimetallic steel bar (BSB) consisting of stainless-steel cladding and carbon steel substrate exhibits excellent corrosion resistance and good mechanical properties. The bimetallic structure of BSBs may affect their low-cycle fatigue performance, and current investigations on the above issue are limited. In this study, the low-cycle fatigue properties of bimetallic steel bars (BSBs) with inelastic buckling were investigated. Experiments and numerical studies were conducted to investigate the low-cycle fatigue capacity for BSBs, considering buckling. The buckling mode of BSBs is discussed. The hysteretic loops and energy properties of BSBs with various slenderness ratios (L/D) and fatigue strain amplitudes (ε_a) are investigated. With increases in the L/D and ε_a, the original symmetry for hysteresis loops disappears gradually, which is caused by the buckling. A predictive equation revealing the relation between the ε_a and fatigue life is suggested, which considers the effects of the L/D. A numerical modelling method is suggested to predict the hysteretic curves of BSBs. The effect of buckling on the stress and energy properties of BSBs is discussed through the numerical analysis of 44 models including the effects of the L/D, ε_a, and cladding ratios. The numerical analysis results illustrate that the hysteresis loops of BSBs with various ε_a values exhibit similar shapes. The increase in the cladding ratio reduces the peak stress and the dissipated energy properties of BSBs. The hysteresis loop energy density decreases by about 3% with an increase of 0.1 in the cladding ratio. It is recommended that the proportion of stainless steel inBSBs should be minimized once the corrosion resistance requirements are met. Full article

(This article belongs to the Special Issue Research Progress of the Fatigue, Crack and Failure Mechanisms of Materials and Structures)

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47 pages, 4047 KiB

Open AccessEditor’s ChoiceReview

Polydopamine Applications in Biomedicine and Environmental Science

by Hossein Omidian and Renae L. Wilson

Materials 2024, 17(16), 3916; https://doi.org/10.3390/ma17163916 - 7 Aug 2024

Cited by 6 | Viewed by 2285

Abstract

This manuscript explores the multifaceted applications of polydopamine (PDA) across various scientific and industrial domains. It covers the chemical aspects of PDA and its potential in bone tissue engineering, implant enhancements, cancer treatment, and nanotechnology. The manuscript investigates PDA’s roles in tissue engineering, [...] Read more.

This manuscript explores the multifaceted applications of polydopamine (PDA) across various scientific and industrial domains. It covers the chemical aspects of PDA and its potential in bone tissue engineering, implant enhancements, cancer treatment, and nanotechnology. The manuscript investigates PDA’s roles in tissue engineering, cell culture technologies, surface modifications, drug delivery systems, and sensing techniques. Additionally, it highlights PDA’s contributions to microfabrication, nanoengineering, and environmental applications. Through detailed testing and assessment, the study identifies limitations in PDA-related research, such as synthesis complexity, incomplete mechanistic understanding, and biocompatibility variability. It also proposes future research directions aimed at improving synthesis techniques, expanding biomedical applications, and enhancing sensing technologies to optimize PDA’s efficacy and scalability. Full article

(This article belongs to the Special Issue Latest Advances in Functional Polymeric Materials for Environmental and Biomedical Applications)

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14 pages, 4592 KiB

Open AccessEditor’s ChoiceArticle

Compressive Properties and Energy Absorption Characteristics of Co-Continuous Interlocking PDMS/PLA Lattice Composites

by Han Wang, Kedi Wang, Jincheng Lei and Xueling Fan

Materials 2024, 17(16), 3894; https://doi.org/10.3390/ma17163894 - 6 Aug 2024

Cited by 1 | Viewed by 1162

Abstract

Co-continuous interlocking lattice structures usually present superior compressive properties and energy absorption characteristics. In this study, co-continuous interlocking polydimethylsiloxane/polylactic acid (PDMS/PLA) lattice composites were designed with different strut diameters, and successfully manufactured by combining the fused deposition modeling (FDM) technique and the infiltration [...] Read more.

Co-continuous interlocking lattice structures usually present superior compressive properties and energy absorption characteristics. In this study, co-continuous interlocking polydimethylsiloxane/polylactic acid (PDMS/PLA) lattice composites were designed with different strut diameters, and successfully manufactured by combining the fused deposition modeling (FDM) technique and the infiltration method. This fabrication method can realize the change and control of structure parameters. The effects of the strut diameter on the compressive properties and energy absorption behavior of PDMS/PLA lattice composites were investigated by using quasi-static compression tests. The compressive properties of the co-continuous interlocking PDMS/PLA lattice composites can be adjusted in a narrow density range by a linear correlation. The energy absorption density of the co-continuous interlocking PDMS/PLA lattice composites increases with the increase in the PLA strut diameter and presents a higher efficiency peak and wider plateau region. The PLA lattice acts as a skeleton and plays an important role in bearing the compressive load and in energy absorption. The indexes of the compressive properties/energy absorption characteristics and PLA volume fraction of co-continuous interlocking PDMS/PLA lattice composites show linear relationships in logarithmic coordinates. The effect of the PLA volume fraction increasing on the plateau stress is more sensitive than the compressive strength and energy absorption density. Full article

(This article belongs to the Special Issue Advances in Structural Design and Numerical Modelling of Composite Materials)

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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 1257

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 12 | Viewed by 4117

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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15 pages, 6045 KiB

Open AccessEditor’s ChoiceArticle

Rheological Changes in Bio-Based Filaments Induced by Extrusion-Based 3D Printing Process

by Antonella Patti and Stefano Acierno

Materials 2024, 17(15), 3839; https://doi.org/10.3390/ma17153839 - 2 Aug 2024

Cited by 2 | Viewed by 1293

Abstract

In this work, the authors investigated the impact of extrusion-based printing process on the structural characteristics of bio-based resins through rheological measurements. Two commercially available filaments made from unfilled and wood-filled polylactide (PLA) polymers were considered. Three-dimensional specimens were prepared by printing these [...] Read more.

In this work, the authors investigated the impact of extrusion-based printing process on the structural characteristics of bio-based resins through rheological measurements. Two commercially available filaments made from unfilled and wood-filled polylactide (PLA) polymers were considered. Three-dimensional specimens were prepared by printing these filaments under various operating conditions, i.e., changing the extruder temperature and printing rate, and examined using time sweep tests. Specific cycle rheological testing was conducted on pelletized filaments to simulate temperature changes in the printing process. The rheological characteristics of unprocessed materials, in terms of storage (G′) and loss (G″) moduli, were found to be slightly affected by temperature changes. For a pure polymer, the G′ slope at a low frequency decreased over time, showing that the polymer chains evolved from a higher to a lower molecular weight. For wood-filled materials, the G′ slope rose over the testing time, emphasizing the formation of a percolated network of structured filler within the matrix. On the other side, the rheological parameters of both materials were strongly impacted by the printing extrusion and the related conditions. At lower nozzle temperatures (200 °C), by decreasing the printing speed, the G′ and G″ curves became increasingly different with respect to unprocessed resin; whereas at higher nozzle temperatures (220 °C), the influence of the printing speed was insignificant, and all curves (albeit distant from those of unprocessed matrix) mainly overlapped. Considerations on degradation kinetics of both materials during the printing process were also provided by fitting experimental data of complex viscosity with linear correlation over time. Full article

(This article belongs to the Special Issue Polymers, Processing and Sustainability)

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