Materials

25 pages, 4500 KiB

Open AccessEditor’s ChoiceArticle

In Vivo Investigation of 3D-Printed Calcium Magnesium Phosphate Wedges in Partial Load Defects

by Elke Hemmerlein, Elke Vorndran, Anna-Maria Schmitt, Franziska Feichtner, Anja-Christina Waselau and Andrea Meyer-Lindenberg

Materials 2024, 17(9), 2136; https://doi.org/10.3390/ma17092136 - 2 May 2024

Viewed by 1192

Abstract

Bone substitutes are ideally biocompatible, osteoconductive, degradable and defect-specific and provide mechanical stability. Magnesium phosphate cements (MPCs) offer high initial stability and faster degradation compared to the well-researched calcium phosphate cements (CPCs). Calcium magnesium phosphate cements (CMPCs) should combine the properties of both [...] Read more.

Bone substitutes are ideally biocompatible, osteoconductive, degradable and defect-specific and provide mechanical stability. Magnesium phosphate cements (MPCs) offer high initial stability and faster degradation compared to the well-researched calcium phosphate cements (CPCs). Calcium magnesium phosphate cements (CMPCs) should combine the properties of both and have so far shown promising results. The present study aimed to investigate and compare the degradation and osseointegration behavior of 3D powder-printed wedges of CMPC and MPC in vivo. The wedges were post-treated with phosphoric acid (CMPC) and diammonium hydrogen phosphate (MPC) and implanted in a partially loaded defect model in the proximal rabbit tibia. The evaluation included clinical, in vivo µ-CT and X-ray examinations, histology, energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) for up to 30 weeks. SEM analysis revealed a zone of unreacted material in the MPC, indicating the need to optimize the manufacturing and post-treatment process. However, all materials showed excellent biocompatibility and mechanical stability. After 24 weeks, they were almost completely degraded. The slower degradation rate of the CMPC corresponded more favorably to the bone growth rate compared to the MPC. Due to the promising results of the CMPC in this study, it should be further investigated, for example in defect models with higher load. Full article

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

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16 pages, 19168 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Long-Term Corrosion Resistance of 316L Stainless Steel by Multilayer Amorphous Carbon Coatings

by Shuyu Li, Hao Li, Peng Guo, Xiaowei Li, Wei Yang, Guanshui Ma, Kazuhito Nishimura, Peiling Ke and Aiying Wang

Materials 2024, 17(9), 2129; https://doi.org/10.3390/ma17092129 - 1 May 2024

Cited by 1 | Viewed by 956

Abstract

Diamond-like carbon (DLC) coatings are effective in protecting the key components of marine equipment and can greatly improve their short-term performance (1.5~4.5 h). However, the lack of investigation into their long-term (more than 200 h) performance cannot meet the service life requirements of [...] Read more.

Diamond-like carbon (DLC) coatings are effective in protecting the key components of marine equipment and can greatly improve their short-term performance (1.5~4.5 h). However, the lack of investigation into their long-term (more than 200 h) performance cannot meet the service life requirements of marine equipment. Here, three multilayered DLC coatings, namely Ti/DLC, TiC_x/DLC, and Ti-TiC_x/DLC, were prepared, and their long-term corrosion resistance was investigated. Results showed that the corrosion current density of all DLC coatings was reduced by 1–2 orders of magnitude compared with bare 316L stainless steel (316Lss). Moreover, under long-term (63 days) immersion in a 3.5 wt.% NaCl solution, all DLC coatings could provide excellent long-term corrosion protection for 316Lss, and Ti-TiC_x/DLC depicted the best corrosion resistance; the polarization resistances remained at ~3.0 × 10⁷ Ω·cm² after immersion for 63 days, with more interfaces to hinder the penetration of the corrosive media. Meanwhile, during neutral salt spray (3000 h), the corrosion resistance of Ti/DLC and TiC_x/DLC coatings showed a certain degree of improvement because the insoluble corrosion products at the defects blocked the subsequent corrosion. This study can provide a route to designing amorphous carbon protective coatings for long-term marine applications in different environments. Full article

(This article belongs to the Special Issue Friction, Corrosion and Protection of Material Surfaces)

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14 pages, 2906 KiB

Open AccessEditor’s ChoiceArticle

First-Principles Study of Adsorption of CH₄ on a Fluorinated Model NiF₂ Surface

by Tilen Lindič and Beate Paulus

Materials 2024, 17(9), 2062; https://doi.org/10.3390/ma17092062 - 27 Apr 2024

Viewed by 1154

Abstract

Electrochemical fluorination on nickel anodes, also known as the Simons’ process, is an important fluorination method used on an industrial scale. Despite its success, the mechanism is still under debate. One of the proposed mechanisms involves higher valent nickel species formed on an [...] Read more.

Electrochemical fluorination on nickel anodes, also known as the Simons’ process, is an important fluorination method used on an industrial scale. Despite its success, the mechanism is still under debate. One of the proposed mechanisms involves higher valent nickel species formed on an anode acting as effective fluorinating agents. Here we report the first attempt to study fluorination by means of first principles investigation. We have identified a possible surface model from the simplest binary nickel fluoride (NiF₂). A twice oxidized NiF₂(F₂) (001) surface exhibits higher valent nickel centers and a fluorination source that can be best characterized as an [F₂]⁻ like unit, readily available to aid fluorination. We have studied the adsorption of CH₄ and the co-adsorption of CH₄ and HF on this surface by means of periodic density functional theory. By the adsorption of CH₄, we found two main outcomes on the surface. Unreactive physisorption of CH₄ and dissociative chemisorption resulting in the formation of CH₃F and HF. The co-adsorption with the HF gave rise to four main outcomes, namely the formation of CH₃F, CH₂F₂, CH₃ radical, and also physisorbed CH₄. Full article

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

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25 pages, 21186 KiB

Open AccessEditor’s ChoiceArticle

Profile Optimisation of a Solid Modular Hob in the Machining of Gears Made of Classic and Unusual, Innovative Materials

by Andrzej Piotrowski and Artur Tyliszczak

Materials 2024, 17(9), 2049; https://doi.org/10.3390/ma17092049 - 26 Apr 2024

Viewed by 964

Abstract

Modular hobs are tools with very complex geometry. Regardless of the material of the gear wheels, they determine the accuracy of the gears made in the hobbing machining process. Gears are made of various, often innovative materials depending on the requirements. Sometimes, the [...] Read more.

Modular hobs are tools with very complex geometry. Regardless of the material of the gear wheels, they determine the accuracy of the gears made in the hobbing machining process. Gears are made of various, often innovative materials depending on the requirements. Sometimes, the materials are characterised by very high hardness (over 65 HRC). The mathematical basis for describing the faces of a hob presented in the article allows for modifying the rack profile shaping the gear wheel’s teeth. The model’s universality makes it possible to perform numerical simulations of the influence of individual parameters of the hob creation process (geometry of the grinding wheels and their setting in the shaping process) on the profile of the rake and flank surfaces. The cutting edge (rack edge) is the locus of points belonging to both of these surfaces and thus directly impacts the accuracy of the gear wheel that is shaped in the hobbing process. The article summarises the authors’ long-term cooperation with the industry, resulting in a series of articles devoted to hobs. The issues presented in the article are significant to the machinery industry and hob manufacturers. Full article

(This article belongs to the Special Issue Modelling, Simulation and Optimisation of Non-Typical and Innovative Materials)

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18 pages, 6871 KiB

Open AccessEditor’s ChoiceArticle

The Use of Wind Turbine Blades to Build Road Noise Barriers as an Example of a Circular Economy Model

by Mirosław Broniewicz, Anna Halicka, Lidia Buda-Ożóg, Filip Broniewicz, Damian Nykiel and Łukasz Jabłoński

Materials 2024, 17(9), 2048; https://doi.org/10.3390/ma17092048 - 26 Apr 2024

Cited by 3 | Viewed by 1358

Abstract

This project’s objective was to create a circular economy in the composites sector by examining the possibility of using wind turbine blade composite materials to construct noise-absorbing barriers for roads. The possibility of constructing road noise barrier panels from components obtained from turbine [...] Read more.

This project’s objective was to create a circular economy in the composites sector by examining the possibility of using wind turbine blade composite materials to construct noise-absorbing barriers for roads. The possibility of constructing road noise barrier panels from components obtained from turbine blades was conceptually examined, and the geometry and construction of wind turbine blades were evaluated for their suitability as filler components for panels. The tensile strength parameters of two types of composites made from windmill blades—a solid composite and a sandwich type—were established based on material tests. The strength of the composite elements cut from a windmill propeller was analyzed, and a three-dimensional numerical model was created using the finite element method. The strength values of the composite used to construct the noise barriers were compared with the stresses resulting from loads operating on the road noise barriers, as determined in compliance with current standards. It was discovered that acoustic screens composed of composite materials derived from wind turbine blades may withstand loads associated with wind pressure and vehicle traffic with sufficient resistance. In order to evaluate the environmental benefits resulting from the use of composite material made from wind turbine blades to make noise barriers, this study presents the values of the embodied energy and embodied carbon for several types of road noise barriers using life cycle assessment. Full article

(This article belongs to the Special Issue Manufacturing of Porous Acoustic Structures and Metamaterials)

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14 pages, 2159 KiB

Open AccessEditor’s ChoiceArticle

A Bioactive Degradable Composite Bone Cement Based on Calcium Sulfate and Magnesium Polyphosphate

by Suping Peng, Xinyue Yang, Wangcai Zou, Xiaolu Chen, Hao Deng, Qiyi Zhang and Yonggang Yan

Materials 2024, 17(8), 1861; https://doi.org/10.3390/ma17081861 - 18 Apr 2024

Viewed by 1308

Abstract

Calcium sulfate bone cement (CSC) is extensively used as a bone repair material due to its ability to self-solidify, degradability, and osteogenic ability. However, the fast degradation, low mechanical strength, and insufficient biological activity limit its application. This study used magnesium polyphosphate (MPP) [...] Read more.

Calcium sulfate bone cement (CSC) is extensively used as a bone repair material due to its ability to self-solidify, degradability, and osteogenic ability. However, the fast degradation, low mechanical strength, and insufficient biological activity limit its application. This study used magnesium polyphosphate (MPP) and constructed a composite bone cement composed of calcium sulfate (CS), MPP, tricalcium silicate (C₃S), and plasticizer hydroxypropyl methylcellulose (HPMC). The optimized CS/MPP/C₃S composite bone cement has a suitable setting time of approximately 15.0 min, a compressive strength of 26.6 MPa, and an injectability of about 93%. The CS/MPP/C₃S composite bone cement has excellent biocompatibility and osteogenic capabilities; our results showed that cell proliferation is up to 114% compared with the control after 5 days. After 14 days, the expression levels of osteogenic-related genes, including Runx2, BMP2, OCN, OPN, and COL-1, are about 1.8, 2.8, 2.5, 2.2, and 2.2 times higher than those of the control, respectively, while the alkaline phosphatase activity is about 1.7 times higher. Therefore, the CS/MPP/C₃S composite bone cement overcomes the limitations of CSC and has more effective potential in bone repair. Full article

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

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16 pages, 2779 KiB

Open AccessEditor’s ChoiceArticle

Rheological and Functional Properties of Mechanically Recycled Post-Consumer Rigid Polyethylene Packaging Waste

by Ezgi Ceren Boz Noyan, Franziska Rehle and Antal Boldizar

Materials 2024, 17(8), 1855; https://doi.org/10.3390/ma17081855 - 17 Apr 2024

Cited by 2 | Viewed by 1699

Abstract

The properties of recycled post-consumer rigid polyethylene packaging waste were studied, using sorted waste washed in the laboratory with water alone and with added detergent, and compared with large-scale high-intensity washed flakes. The washed flakes were compounded using three different temperature profiles in [...] Read more.

The properties of recycled post-consumer rigid polyethylene packaging waste were studied, using sorted waste washed in the laboratory with water alone and with added detergent, and compared with large-scale high-intensity washed flakes. The washed flakes were compounded using three different temperature profiles in a twin-screw extruder and then injection molded. A higher compounding temperature reduced the thermo-oxidative stability, the average molecular mass, and the viscosity of the samples. Rheological measurements suggested that changes in chain branching occurred at different compounding temperatures. The strength and the elongation at break were also influenced by the compounding temperature in both the molten and solid states. Detergent washing maintained the thermo-oxidative stability in contrast to washing with water. The large-scale washed samples had a relatively high thermo-oxidative stability, a higher melt elasticity, and a lower elongation at break in both the molten and solid states than the laboratory-scale washed samples. The thermal properties, melt elasticity, Young’s modulus, yield stress, and yield strain of the samples were not, however, significantly affected by either the compounding temperature or the washing medium and intensity. The results indicated that recycled post-consumer rigid polyethylene packaging waste has properties that can support further applications in new products. Full article

(This article belongs to the Special Issue Polymers: From Waste to Potential Reuse)

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15 pages, 11880 KiB

Open AccessEditor’s ChoiceArticle

Medium- and High-Entropy Rare Earth Hexaborides with Enhanced Solar Energy Absorption and Infrared Emissivity

by Hongye Wang, Yanyu Pan, Jincheng Zhang, Kaixian Wang, Liyan Xue, Minzhong Huang, Yazhu Li, Fan Yang and Heng Chen

Materials 2024, 17(8), 1789; https://doi.org/10.3390/ma17081789 - 12 Apr 2024

Cited by 2 | Viewed by 1074

Abstract

The development of a new generation of solid particle solar receivers (SPSRs) with high solar absorptivity (0.28–2.5 μm) and high infrared emissivity (1–22 μm) is crucial and has attracted much attention for the attainment of the goals of “peak carbon” and “carbon neutrality”. [...] Read more.

The development of a new generation of solid particle solar receivers (SPSRs) with high solar absorptivity (0.28–2.5 μm) and high infrared emissivity (1–22 μm) is crucial and has attracted much attention for the attainment of the goals of “peak carbon” and “carbon neutrality”. To achieve the modulation of infrared emission and solar absorptivity, two types of medium- and high-entropy rare-earth hexaboride (ME/HEREB₆) ceramics, (La_0.25Sm_0.25Ce_0.25Eu_0.25)B₆ (MEREB₆) and (La_0.2Sm_0.2Ce_0.2Eu_0.2Ba_0.2)B₆ (HEREB₆), with severe lattice distortions were synthesized using a high-temperature solid-phase method. Compared to single-phase lanthanum hexaboride (LaB₆), HEREB₆ ceramics show an increase in solar absorptivity from 54.06% to 87.75% in the range of 0.28–2.5 μm and an increase in infrared emissivity from 76.19% to 89.96% in the 1–22 μm wavelength range. On the one hand, decreasing the free electron concentration and the plasma frequency reduces the reflection and ultimately increases the solar absorptivity. On the other hand, the lattice distortion induces changes in the B–B bond length, leading to significant changes in the Raman scattering spectrum, which affects the damping constant and ultimately increases the infrared emissivity. In conclusion, the multicomponent design can effectively improve the solar energy absorption and heat transfer capacity of ME/HEREB₆, thus providing a new avenue for the development of solid particles. Full article

(This article belongs to the Special Issue Design, Processing and Properties of High Entropy Ceramics)

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19 pages, 464 KiB

Open AccessEditor’s ChoiceReview

Nanostructured Medical Devices: Regulatory Perspective and Current Applications

by Giuseppe D’Avenio, Carla Daniele and Mauro Grigioni

Materials 2024, 17(8), 1787; https://doi.org/10.3390/ma17081787 - 12 Apr 2024

Cited by 2 | Viewed by 1573

Abstract

Nanomaterials (NMs) are having a huge impact in several domains, including the fabrication of medical devices (MDs). Hence, nanostructured MDs are becoming quite common; nevertheless, the associated risks must be carefully considered in order to demonstrate safety prior to their immission on the [...] Read more.

Nanomaterials (NMs) are having a huge impact in several domains, including the fabrication of medical devices (MDs). Hence, nanostructured MDs are becoming quite common; nevertheless, the associated risks must be carefully considered in order to demonstrate safety prior to their immission on the market. The biological effect of NMs requires the consideration of methodological issues since already established methods for, e.g., cytotoxicity can be subject to a loss of accuracy in the presence of certain NMs. The need for oversight of MDs containing NMs is reflected by the European Regulation 2017/745 on MDs, which states that MDs incorporating or consisting of NMs are in class III, at highest risk, unless the NM is encapsulated or bound in such a manner that the potential for its internal exposure is low or negligible (Rule 19). This study addresses the role of NMs in medical devices, highlighting the current applications and considering the regulatory requirements of such products. Full article

(This article belongs to the Special Issue Advanced Functional Nanomaterials for Biomedical Application)

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21 pages, 11311 KiB

Open AccessEditor’s ChoiceArticle

Investigating the Impact Behavior of Carbon Fiber/Polymethacrylimide (PMI) Foam Sandwich Composites for Personal Protective Equipment

by Xinyu Zhang, Miao Tian, Jun Li and Xinggang Chen

Materials 2024, 17(7), 1683; https://doi.org/10.3390/ma17071683 - 6 Apr 2024

Viewed by 1392

Abstract

To improve the shock resistance of personal protective equipment and reduce casualties due to shock wave accidents, this study prepared four types of carbon fiber/polymethacrylimide (PMI) foam sandwich panels with different face/back layer thicknesses and core layer densities and subjected them to quasi-static [...] Read more.

To improve the shock resistance of personal protective equipment and reduce casualties due to shock wave accidents, this study prepared four types of carbon fiber/polymethacrylimide (PMI) foam sandwich panels with different face/back layer thicknesses and core layer densities and subjected them to quasi-static compression, low-speed impact, high-speed impact, and non-destructive tests. The mechanical properties and energy absorption capacities of the impact-resistant panels, featuring ceramic/ultra-high molecular-weight polyethylene (UHMWPE) and carbon fiber/PMI foam structures, were evaluated and compared, and the feasibility of using the latter as a raw material for personal impact-resistant equipment was also evaluated. For the PMI sandwich panel with a constant total thickness, increasing the core layer density and face/back layer thickness enhanced the energy absorption capacity, and increased the peak stress of the face layer. Under a constant strain, the energy absorption value of all specimens increased with increasing impact speed. When a 10 kg hammer impacted the specimen surface at a speed of 1.5 m/s, the foam sandwich panels retained better integrity than the ceramic/UHMWPE panel. The results showed that the carbon fiber/PMI foam sandwich panels were suitable for applications that require the flexible movement of the wearer under shock waves, and provide an experimental basis for designing impact-resistant equipment with low weight, high strength, and high energy absorption capacities. Full article

(This article belongs to the Special Issue Recent Progress in Functional Materials and Their Applications)

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15 pages, 4319 KiB

Open AccessEditor’s ChoiceArticle

Machine Learning Prediction of Quantum Yields and Wavelengths of Aggregation-Induced Emission Molecules

by Hele Bi, Jiale Jiang, Junzhao Chen, Xiaojun Kuang and Jinxiao Zhang

Materials 2024, 17(7), 1664; https://doi.org/10.3390/ma17071664 - 4 Apr 2024

Viewed by 1422

Abstract

The aggregation-induced emission (AIE) effect exhibits a significant influence on the development of luminescent materials and has made remarkable progress over the past decades. The advancement of high-performance AIE materials requires fast and accurate predictions of their photophysical properties, which is impeded by [...] Read more.

The aggregation-induced emission (AIE) effect exhibits a significant influence on the development of luminescent materials and has made remarkable progress over the past decades. The advancement of high-performance AIE materials requires fast and accurate predictions of their photophysical properties, which is impeded by the inherent limitations of quantum chemical calculations. In this work, we present an accurate machine learning approach for the fast predictions of quantum yields and wavelengths to screen out AIE molecules. A database of about 563 organic luminescent molecules with quantum yields and wavelengths in the monomeric/aggregated states was established. Individual/combined molecular fingerprints were selected and compared elaborately to attain appropriate molecular descriptors. Different machine learning algorithms combined with favorable molecular fingerprints were further screened to achieve more accurate prediction models. The simulation results indicate that combined molecular fingerprints yield more accurate predictions in the aggregated states, and random forest and gradient boosting regression algorithms show the best predictions in quantum yields and wavelengths, respectively. Given the successful applications of machine learning in quantum yields and wavelengths, it is reasonable to anticipate that machine learning can serve as a complementary strategy to traditional experimental/theoretical methods in the investigation of aggregation-induced luminescent molecules to facilitate the discovery of luminescent materials. Full article

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

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Graphical abstract

7 pages, 1884 KiB

Open AccessEditor’s ChoiceCommunication

Three-Dimensional Epitaxy of Low-Defect 3C-SiC on a Geometrically Modified Silicon Substrate

by Gerard Colston, Kelly Turner, Arne Renz, Kushani Perera, Peter M. Gammon, Marina Antoniou and Vishal A. Shah

Materials 2024, 17(7), 1587; https://doi.org/10.3390/ma17071587 - 30 Mar 2024

Viewed by 993

Abstract

We demonstrate the growth of 3C-SiC with reduced planar defects on a micro-scale compliant substrate. Heteroepitaxial growth of 3C-SiC on trenches with a width and separation of 2 µm, etched into a Si(001) substrate, is found to suppress defect propagation through the epilayer. [...] Read more.

We demonstrate the growth of 3C-SiC with reduced planar defects on a micro-scale compliant substrate. Heteroepitaxial growth of 3C-SiC on trenches with a width and separation of 2 µm, etched into a Si(001) substrate, is found to suppress defect propagation through the epilayer. Stacking faults and other planar defects are channeled away from the center of the patterned structures, which are rounded through the use of H₂ annealing at 1100 °C. Void formation between the columns of 3C-SiC growth acts as a termination point for defects, and coalescence of these columns into a continuous epilayer is promoted through the addition of HCl in the growth phase. The process of fabricating these compliant substrates utilizes standard processing techniques found within the semiconductor industry and is independent of the substrate orientation and offcut. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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13 pages, 11887 KiB

Open AccessEditor’s ChoiceArticle

Degradation of Poly(ethylene terephthalate) Catalyzed by Nonmetallic Dibasic Ionic Liquids under UV Radiation

by Ruiqi Zhang, Xu Zheng, Xiujie Cheng, Junli Xu, Yi Li, Qing Zhou, Jiayu Xin, Dongxia Yan and Xingmei Lu

Materials 2024, 17(7), 1583; https://doi.org/10.3390/ma17071583 - 29 Mar 2024

Cited by 2 | Viewed by 1180

Abstract

Nonmetallic ionic liquids (ILs) exhibit unique advantages in catalyzing poly (ethylene terephthalate) (PET) glycolysis, but usually require longer reaction times. We found that exposure to UV radiation can accelerate the glycolysis reaction and significantly reduce the reaction time. In this work, we synthesized [...] Read more.

Nonmetallic ionic liquids (ILs) exhibit unique advantages in catalyzing poly (ethylene terephthalate) (PET) glycolysis, but usually require longer reaction times. We found that exposure to UV radiation can accelerate the glycolysis reaction and significantly reduce the reaction time. In this work, we synthesized five nonmetallic dibasic ILs, and their glycolysis catalytic activity was investigated. 1,8-diazabicyclo [5,4,0] undec-7-ene imidazole ([HDBU]Im) exhibited better catalytic performance. Meanwhile, UV radiation is used as a reinforcement method to improve the PET glycolysis efficiency. Under optimal conditions (5 g PET, 20 g ethylene glycol (EG), 0.25 g [HDBU]Im, 10,000 µW·cm⁻² UV radiation reacted for 90 min at 185 °C), the PET conversion and BHET yield were 100% and 88.9%, respectively. Based on the UV-visible spectrum, it was found that UV radiation can activate the C=O in PET. Hence, the incorporation of UV radiation can considerably diminish the activation energy of the reaction, shortening the reaction time of PET degradation. Finally, a possible reaction mechanism of [HDBU]Im-catalyzed PET glycolysis under UV radiation was proposed. Full article

(This article belongs to the Special Issue Recent Researches in Polymer and Plastic Processing)

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15 pages, 6948 KiB

Open AccessEditor’s ChoiceArticle

Enhancement of Strength–Ductility Synergy of Al-Li Cast Alloy via New Forming Processes and Sc Addition

by Shulin Lü, Zhaoxiang Yan, Yu Pan, Jianyu Li, Shusen Wu and Wei Guo

Materials 2024, 17(7), 1558; https://doi.org/10.3390/ma17071558 - 28 Mar 2024

Viewed by 1052

Abstract

In this study, concurrent enhancements in both strength and ductility of the Al-2Li-2Cu-0.5Mg-0.2Zr cast alloy (hereafter referred to as Al-Li) were achieved through an optimized forming process comprising ultrasonic treatment followed by squeeze casting, coupled with the incorporation of Sc. Initially, the variations [...] Read more.

In this study, concurrent enhancements in both strength and ductility of the Al-2Li-2Cu-0.5Mg-0.2Zr cast alloy (hereafter referred to as Al-Li) were achieved through an optimized forming process comprising ultrasonic treatment followed by squeeze casting, coupled with the incorporation of Sc. Initially, the variations in the microstructure and mechanical properties of the Sc-free Al-Li cast alloy (i.e., alloy A) during various forming processes were investigated. The results revealed that the grain size in the UT+SC (ultrasonic treatment + squeeze casting) alloy was reduced by 76.3% and 57.7%, respectively, compared to those of the GC (gravity casting) or SC alloys. Additionally, significant improvements were observed in its compositional segregation and porosity reduction. After UT+SC, the ultimate tensile strength (UTS), yield strength (YS), and elongation reached 235 MPa, 135 MPa, and 15%, respectively, which were 113.6%, 28.6%, and 1150% higher than those of the GC alloy. Subsequently, the Al-Li cast alloy containing 0.2 wt.% Sc (referred to as alloy B) exhibited even finer grains under the UT+SC process, resulting in simultaneous enhancements in its UTS, YS, and elongation. Interestingly, the product of ultimate tensile strength and elongation (i.e., UTS × EL) for both alloys reached 36 GPa•% and 42 GPa•%, respectively, which is much higher than that of other Al-Li cast alloys reported in the available literature. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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26 pages, 8501 KiB

Open AccessEditor’s ChoiceArticle

Process–Structure–Property Relationship Development in Large-Format Additive Manufacturing: Fiber Alignment and Ultimate Tensile Strength

by Lucinda K. Slattery, Zackery B. McClelland and Samuel T. Hess

Materials 2024, 17(7), 1526; https://doi.org/10.3390/ma17071526 - 27 Mar 2024

Cited by 1 | Viewed by 1236

Abstract

Parts made through additive manufacturing (AM) often exhibit mechanical anisotropy due to the time-based deposition of material and processing parameters. In polymer material extrusion (MEX), printed parts have weak points at layer interfaces, perpendicular to the direction of deposition. Poly(lactic acid) with chopped [...] Read more.

Parts made through additive manufacturing (AM) often exhibit mechanical anisotropy due to the time-based deposition of material and processing parameters. In polymer material extrusion (MEX), printed parts have weak points at layer interfaces, perpendicular to the direction of deposition. Poly(lactic acid) with chopped carbon fiber was printed on a large-format pellet printer at various extrusion rates with the same tool pathing to measure the fiber alignment with deposition via two methods and relate it to the ultimate tensile strength (UTS). Within a singular printed bead, an X-ray microscopy (XRM) scan was conducted to produce a reconstruction of the internal microstructure and 3D object data on the length and orientation of fibers. From the scan, discrete images were used in an image analysis technique to determine the fiber alignment to deposition without 3D object data on each fiber’s size. Both the object method and the discrete image method showed a negative relationship between the extrusion rate and fiber alignment, with −34.64% and −53.43% alignment per extrusion multiplier, respectively, as the slopes of the linear regression. Tensile testing was conducted to determine the correlation between the fiber alignment and UTS. For all extrusion rates tested, as the extrusion multiplier increased, the percent difference in the UTS decreased, to a minimum of 8.12 ± 14.40%. The use of image analysis for the determination of the fiber alignment provides a possible method for relating the microstructure to the meso-property of AM parts, and the relationship between the microstructure and the properties establishes process–structure–property relationships for large-format AM. Full article

(This article belongs to the Special Issue Additive Manufacturing of Polymer-Fiber Composites)

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11 pages, 2225 KiB

Open AccessEditor’s ChoiceArticle

In Vitro Study on the Influence of the Buccal Surface Convexity of the Tooth upon Enamel Loss after Bracket Removal

by Sandra Pallarés-Serrano, Alba Pallarés-Serrano, Antonio Pallarés-Serrano and Antonio Pallarés-Sabater

Materials 2024, 17(7), 1519; https://doi.org/10.3390/ma17071519 - 27 Mar 2024

Cited by 1 | Viewed by 915

Abstract

Polishing after the removal of brackets is the final step in orthodontic treatment. It is simple to perform, though some studies have reported that polishing causes damage to the enamel surface. An in vitro study was made of the influence of the buccal [...] Read more.

Polishing after the removal of brackets is the final step in orthodontic treatment. It is simple to perform, though some studies have reported that polishing causes damage to the enamel surface. An in vitro study was made of the influence of the buccal surface convexity of the tooth upon possible enamel loss when the remaining resin and adhesive are removed after bracket decementing using two different polishing modes: a tungsten carbide bur at low and high speeds. The convexity of the buccal surface was quantified in 30 incisors and 30 premolars. A stereoscopic microscope was used to obtain photographs of the profile of the crown, and Image J software was used to calculate convexity by dividing the length of a line from the cementoenamel junction to the incisal margin by another line from the mentioned junction to the maximum convexity of the buccal surface. Brackets were cemented on all the teeth and were decemented 24 h later. In both groups, the residual composite was removed with a tungsten carbide bur at a low speed in one-half of the teeth and at a high speed in the other half. The buccal surface of each tooth was then photographed again, and the convexity was calculated and compared against the baseline value. The difference between the two values were taken to represent the enamel loss. The convexity of the premolars was significantly greater than that of the incisors, but this did not result in greater enamel loss when the same polishing mode was used. However, the tungsten carbide bur at a high speed proved more aggressive, causing significantly greater enamel loss than when used at a low speed. Full article

(This article belongs to the Special Issue Latest Research on Advanced Materials and Technologies in Orthodontics)

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15 pages, 6758 KiB

Open AccessEditor’s ChoiceArticle

Modeling of Charge-to-Breakdown with an Electron Trapping Model for Analysis of Thermal Gate Oxide Failure Mechanism in SiC Power MOSFETs

by Jiashu Qian, Limeng Shi, Michael Jin, Monikuntala Bhattacharya, Atsushi Shimbori, Hengyu Yu, Shiva Houshmand, Marvin H. White and Anant K. Agarwal

Materials 2024, 17(7), 1455; https://doi.org/10.3390/ma17071455 - 22 Mar 2024

Cited by 3 | Viewed by 1383

Abstract

The failure mechanism of thermal gate oxide in silicon carbide (SiC) power metal oxide semiconductor field effect transistors (MOSFETs), whether it is field-driven breakdown or charge-driven breakdown, has always been a controversial topic. Previous studies have demonstrated that the failure time of thermally [...] Read more.

The failure mechanism of thermal gate oxide in silicon carbide (SiC) power metal oxide semiconductor field effect transistors (MOSFETs), whether it is field-driven breakdown or charge-driven breakdown, has always been a controversial topic. Previous studies have demonstrated that the failure time of thermally grown silicon dioxide (SiO₂) on SiC stressed with a constant voltage is indicated as charge driven rather than field driven through the observation of Weibull Slope β. Considering the importance of the accurate failure mechanism for the thermal gate oxide lifetime prediction model of time-dependent dielectric breakdown (TDDB), charge-driven breakdown needs to be further fundamentally justified. In this work, the charge-to-breakdown (

Q_{B D}

) of the thermal gate oxide in a type of commercial planar SiC power MOSFETs, under the constant current stress (CCS), constant voltage stress (CVS), and pulsed voltage stress (PVS) are extracted, respectively. A mathematical electron trapping model in thermal SiO₂ grown on single crystal silicon (Si) under CCS, which was proposed by M. Liang et al., is proven to work equally well with thermal SiO₂ grown on SiC and used to deduce the

Q_{B D}

model of the device under test (DUT). Compared with the

Q_{B D}

obtained under the three stress conditions, the charge-driven breakdown mechanism is validated in the thermal gate oxide of SiC power MOSFETs. Full article

(This article belongs to the Special Issue Silicon Carbide: Material Growth, Device Processing and Applications)

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14 pages, 6419 KiB

Open AccessEditor’s ChoiceArticle

Tailoring Iridium Valence States on ZSM-5 for Enhanced Catalytic Performance in CO Selective Catalytic Reduction of NO under Oxygen-Enriched Environments

by Yarong Bai, Chuhan Miao, Weilong Ouyang, Lang Wang, Haiqiang Wang and Zhongbiao Wu

Materials 2024, 17(6), 1440; https://doi.org/10.3390/ma17061440 - 21 Mar 2024

Viewed by 1071

Abstract

Barium and iridium supported on Zeolite Socony Mobil-5 (ZSM-5) are efficient catalysts for the selective catalytic reduction of nitric oxide by carbon monoxide (CO-SCR), with enhanced cyclic stability. The introduction of Ba hindered the oxidation of metallic Ir active species and enabled Ir [...] Read more.

Barium and iridium supported on Zeolite Socony Mobil-5 (ZSM-5) are efficient catalysts for the selective catalytic reduction of nitric oxide by carbon monoxide (CO-SCR), with enhanced cyclic stability. The introduction of Ba hindered the oxidation of metallic Ir active species and enabled Ir to maintain an active metallic state, thereby preventing a decrease in catalytic activity in the CO-SCR reaction. Moreover, the Ba modification increased the NO adsorption of the catalyst, further improving the catalytic activity. Owing to the better anti-oxidation ability of Ir⁰ in IrBa0.2/ZSM-5(27) than in Ir/ZSM-5(27), IrBa0.2/ZSM-5(27) showed better stability than Ir/ZSM-5(27). Considering that all samples in the present study were tested to simulate actual flue gases (such as sintering flue gas and coke oven flue gas), NH₃ was introduced into the reaction system to serve as an extra reductant for NO_x. The NO_x conversion to N₂ (77.1%) was substantially improved using the NH₃-CO-SCR system. The proposed catalysts and reaction systems are promising alternatives for treating flue gas, which contains considerable amounts of NO_x and CO in oxygen-enriched environments. Full article

(This article belongs to the Section Catalytic Materials)

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12 pages, 8092 KiB

Open AccessEditor’s ChoiceArticle

A Study of the Adsorption Properties of Individual Atoms on the Graphene Surface: Density Functional Theory Calculations Assisted by Machine Learning Techniques

by Jingtao Huang, Mo Chen, Jingteng Xue, Mingwei Li, Yuan Cheng, Zhonghong Lai, Jin Hu, Fei Zhou, Nan Qu, Yong Liu and Jingchuan Zhu

Materials 2024, 17(6), 1428; https://doi.org/10.3390/ma17061428 - 20 Mar 2024

Cited by 1 | Viewed by 1186

Abstract

In this research, the adsorption performance of individual atoms on the surface of monolayer graphene surface was systematically investigated using machine learning methods to accelerate density functional theory. The adsorption behaviors of over thirty different atoms on the graphene surface were computationally analyzed. [...] Read more.

In this research, the adsorption performance of individual atoms on the surface of monolayer graphene surface was systematically investigated using machine learning methods to accelerate density functional theory. The adsorption behaviors of over thirty different atoms on the graphene surface were computationally analyzed. The adsorption energy and distance were extracted as the research targets, and the basic information of atoms (such as atomic radius, ionic radius, etc.) were used as the feature values to establish the dataset. Through feature engineering selection, the corresponding input feature values for the input-output relationship were determined. By comparing different models on the dataset using five-fold cross-validation, the mathematical model that best fits the dataset was identified. The optimal model was further fine-tuned by adjusting of the best mathematical ML model. Subsequently, we verified the accuracy of the established machine learning model. Finally, the precision of the machine learning model forecasts was verified by the method of comparing and contrasting machine learning results with density functional theory. The results suggest that elements such as Zr, Ti, Sc, and Si possess some potential in controlling the interfacial reaction of graphene/aluminum composites. By using machine learning to accelerate first-principles calculations, we have further expanded our choice of research methods and accelerated the pace of studying element–graphene interactions. Full article

(This article belongs to the Special Issue Adsorption Materials and Their Applications)

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23 pages, 30993 KiB

Open AccessEditor’s ChoiceArticle

Numerical Simulation and Machine Learning Prediction of the Direct Chill Casting Process of Large-Scale Aluminum Ingots

by Guanhua Guo, Ting Yao, Wensheng Liu, Sai Tang, Daihong Xiao, Lanping Huang, Lei Wu, Zhaohui Feng and Xiaobing Gao

Materials 2024, 17(6), 1409; https://doi.org/10.3390/ma17061409 - 19 Mar 2024

Viewed by 1828

Abstract

The large-scale ingot of the 7xxx-series aluminum alloys fabricated by direct chill (DC) casting often suffers from foundry defects such as cracks and cold shut due to the formidable challenges in the precise controlling of casting parameters. In this manuscript, by using the [...] Read more.

The large-scale ingot of the 7xxx-series aluminum alloys fabricated by direct chill (DC) casting often suffers from foundry defects such as cracks and cold shut due to the formidable challenges in the precise controlling of casting parameters. In this manuscript, by using the integrated computational method combining numerical simulations with machine learning, we systematically estimated the evolution of multi-physical fields and grain structures during the solidification processes. The numerical simulation results quantified the influences of key casting parameters including pouring temperature, casting speed, primary cooling intensity, and secondary cooling water flow rate on the shape of the mushy zone, heat transport, residual stress, and grain structure of DC casting ingots. Then, based on the data of numerical simulations, we established a novel model for the relationship between casting parameters and solidification characteristics through machine learning. By comparing it with experimental measurements, the model showed reasonable accuracy in predicting the sump profile, microstructure evolution, and solidification kinetics under the complicated influences of casting parameters. The integrated computational method and predicting model could be used to efficiently and accurately determine the DC casting parameters to decrease the casting defects. Full article

(This article belongs to the Section Metals and Alloys)

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13 pages, 4191 KiB

Open AccessEditor’s ChoiceArticle

Thermal Transitions and Structural Characteristics of Poly(3,4-ethylenedioxythiophene/cucurbit[7]uril) Polypseudorotaxane and Polyrotaxane Thin Films

by Barbara Hajduk, Paweł Jarka, Henryk Bednarski, Henryk Janeczek, Pallavi Kumari and Aurica Farcas

Materials 2024, 17(6), 1318; https://doi.org/10.3390/ma17061318 - 13 Mar 2024

Viewed by 1329

Abstract

Herein, we report the thermal transitions and structural properties of poly(3,4-ethylenedioxythiophene/cucurbit[7]uril) pseudopolyrotaxane (PEDOT∙CB7-PS) and polyrotaxane (PEDOT∙CB7-PR) thin films compared with those of pristine PEDOT. The structural characteristics were investigated by using variable-temperature spectroscopic ellipsometry (VTSE), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and [...] Read more.

Herein, we report the thermal transitions and structural properties of poly(3,4-ethylenedioxythiophene/cucurbit[7]uril) pseudopolyrotaxane (PEDOT∙CB7-PS) and polyrotaxane (PEDOT∙CB7-PR) thin films compared with those of pristine PEDOT. The structural characteristics were investigated by using variable-temperature spectroscopic ellipsometry (VTSE), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and atomic force microscopy (AFM). VTSE and DSC results indicated the presence of an endothermic process and glass transition in the PEDOT∙CB7-PS and PEDOT∙CB7-PR thin films. X-ray diffraction of PEDOT∙CB7-PS and PEDOT∙CB7-PR powders displayed the presence of interchain π-π stacking revealing a characteristic arrangement of aromatic rings in the internal structure of the crystallites. AFM imaging of PEDOT∙CB7-PS and PEDOT∙CB7-PR thin films exhibited significant differences in the surface topographies compared with those of PEDOT. A high degree of crystallization was clearly visible on the surface of the PEDOT layer, whereas the PEDOT∙CB7-PS and PEDOT∙CB7-PR thin films exhibited more favorable surface parameters. Such significant differences identified in the surface morphology of the investigated layers can, therefore, be clearly associated with the presence of surrounding CB7 on PEDOT skeletons. Full article

(This article belongs to the Special Issue Hyperbranched Macromolecular Architectures: From Design to Applications)

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17 pages, 3440 KiB

Open AccessEditor’s ChoiceArticle

Structure, Antioxidant Activity and Antimicrobial Study of Light Lanthanide Complexes with p-Coumaric Acid

by Grzegorz Świderski, Ewelina Gołębiewska, Natalia Kowalczyk, Monika Kalinowska, Renata Świsłocka, Elżbieta Wołejko, Urszula Wydro, Piotr Malinowski, Anna Pietryczuk, Adam Cudowski, Waldemar Priebe and Włodzimierz Lewandowski

Materials 2024, 17(6), 1324; https://doi.org/10.3390/ma17061324 - 13 Mar 2024

Cited by 1 | Viewed by 1335

Abstract

This paper presents the results of a study of the effects of the lanthanide ions Ce³⁺, Pr³⁺, Nd³⁺ and Sm³⁺ on the electronic structure and antioxidant and biological (antimicrobial and cytotoxic) properties of p-coumaric acid (p-CAH₂ [...] Read more.

This paper presents the results of a study of the effects of the lanthanide ions Ce³⁺, Pr³⁺, Nd³⁺ and Sm³⁺ on the electronic structure and antioxidant and biological (antimicrobial and cytotoxic) properties of p-coumaric acid (p-CAH₂). Structural studies were conducted via spectroscopic methods (FTIR, ATR, UV). Thermal degradation studies of the complexes were performed. The results are presented in the form of TG, DTG and DSC curves. Antioxidant properties were determined via activity tests against DPPH, ABTS and OH radicals. The reducing ability was tested via CUPRAC assays. Minimum inhibitory concentrations (MICs) of the ligand and lanthanide complexes were determined on E. coli, B. subtilis and C. albicans microorganisms. The antimicrobial activity was also determined using the MTT assay. The results were presented as the relative cell viability of C. albicans, P. aeruginosa, E. coli and S. aureus compared to controls and expressed as percentages. In the obtained complexes in the solid phase, lanthanide ions coordinate three ligands in a bidentate chelating coordination mode through the carboxyl group of the acid. Spectroscopic analysis showed that lanthanide ions increase the aromaticity of the pi electron system of the ligand. Thermal analysis showed that the complexes are hydrated and have a higher thermal stability than the ligand. The products of thermal decomposition of the complexes are lanthanide oxides. In the aqueous phase, the metal combines with the ligand in a 1:1 molar ratio. Antioxidant activity tests showed that the complexes have a similar ability to remove free radicals. ABTS and DPPH tests showed that the complexes have twice the ability to neutralise radicals than the ligand, and a much higher ability to remove the hydroxyl radical. The abilities of the complexes and the free ligand to reduce Cu2+ ions in the CUPRAC test are at a similar level. Lanthanide complexes of p-coumaric acid are characterised by a higher antimicrobial capacity than the free ligand against Escherichia coli bacteria, Bacillus subtilis and Candida albicans fungi. Full article

(This article belongs to the Special Issue Synthesis, Modeling, Physico-Chemical and Biological Properties of Metal Complexes)

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11 pages, 688 KiB

Open AccessEditor’s ChoiceArticle

Anisotropic Local Structure of SrFe_2−xNi_xAs₂ (x = 0.00, 0.16, and 0.23) Superconductor Probed by Polarized X-ray Absorption Fine Structure Measurements

by M. Y. Hacisalihoglu, L. Tortora, G. Tomassucci, L. Simonelli and N. L. Saini

Materials 2024, 17(6), 1301; https://doi.org/10.3390/ma17061301 - 11 Mar 2024

Viewed by 1052

Abstract

We have investigated the effect of the Ni substitution on the local structure and the valence electronic states of the

{SrFe}_{2 - x}

{Ni}_{x}

{As}_{2}

(x = 0.00, 0.16, and 0.23) superconductor with a multi-edge extended X-ray absorption fine structure [...] Read more.

We have investigated the effect of the Ni substitution on the local structure and the valence electronic states of the

{SrFe}_{2 - x}

{Ni}_{x}

{As}_{2}

(x = 0.00, 0.16, and 0.23) superconductor with a multi-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopy. The As K-edge and Fe K-edge EXAFS measurements in the two polarizations (E‖ab and E‖c) show a clear change in the local structure with Ni concentration. The near-neighbor bondlengths and the related mean-square relative displacements (MSRDs) decrease as the Ni content increases. The polarized XANES spectra at the As, Fe and Ni K edges reveal a systematic change in the anisotropy of the valence electronic structure. The results suggest that the quasi 2D electronic structure of this system tends to become more isotropic as the Ni content increases. The local structure and the valence electronic states are discussed in the frame of the evolving electronic transport of the

{SrFe}_{2 - x}

{Ni}_{x}

{As}_{2}

system. Full article

(This article belongs to the Special Issue Structure and Electronic Properties of Emerging Superconductor and Related Materials)

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29 pages, 7292 KiB

Open AccessEditor’s ChoiceReview

A Review on Additive Manufacturing Methods for NiTi Shape Memory Alloy Production

by Kristýna Kubášová, Veronika Drátovská, Monika Losertová, Pavel Salvetr, Michal Kopelent, Filip Kořínek, Vojtěch Havlas, Ján Džugan and Matej Daniel

Materials 2024, 17(6), 1248; https://doi.org/10.3390/ma17061248 - 8 Mar 2024

Cited by 4 | Viewed by 3228

Abstract

The NiTi alloy, known as Nitinol, represents one of the most investigated smart alloys, exhibiting a shape memory effect and superelasticity. These, among many other remarkable attributes, enable its utilization in various applications, encompassing the automotive industry, aviation, space exploration, and, notably, medicine. [...] Read more.

The NiTi alloy, known as Nitinol, represents one of the most investigated smart alloys, exhibiting a shape memory effect and superelasticity. These, among many other remarkable attributes, enable its utilization in various applications, encompassing the automotive industry, aviation, space exploration, and, notably, medicine. Conventionally, Nitinol is predominantly produced in the form of wire or thin sheets that allow producing many required components. However, the manufacturing of complex shapes poses challenges due to the tenacity of the NiTi alloy, and different processing routes at elevated temperatures have to be applied. Overcoming this obstacle may be facilitated by additive manufacturing methods. This article provides an overview of the employment of additive manufacturing methods, allowing the preparation of the required shapes of Nitinol products while retaining their exceptional properties and potential applications. Full article

(This article belongs to the Special Issue Three-Dimensional Printing Techniques for Biomedical Applications)

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23 pages, 15469 KiB

Open AccessEditor’s ChoiceArticle

Interfacial Segregation of Sn during the Continuous Annealing and Selective Oxidation of Fe-Mn-Sn Alloys

by Jonas Wagner and Joseph R. McDermid

Materials 2024, 17(6), 1257; https://doi.org/10.3390/ma17061257 - 8 Mar 2024

Cited by 1 | Viewed by 914

Abstract

The effect of Mn on interfacial Sn segregation during the selective oxidation of Fe-(0–10)Mn-0.03Sn (at.%) alloys was determined for annealing conditions compatible with continuous galvanizing. Significant Sn enrichment was observed at the substrate free surface and metal/oxide interface for all annealing conditions and [...] Read more.

The effect of Mn on interfacial Sn segregation during the selective oxidation of Fe-(0–10)Mn-0.03Sn (at.%) alloys was determined for annealing conditions compatible with continuous galvanizing. Significant Sn enrichment was observed at the substrate free surface and metal/oxide interface for all annealing conditions and Mn levels. Sn enrichment at the free surface was insensitive to the Mn alloy concentration, which was partially attributed to the opposing effects of Mn on segregation thermodynamics and kinetics: Mn increases the driving force for Sn segregation via reducing Sn solubility in Fe but also reduces the effective Sn diffusivity by increasing the austenite volume fraction. This insensitivity was exacerbated by the depletion of solute Mn near the surface due to the selective oxidation of Mn. Thus, Sn segregation occurred in regions with a local Mn concentration lower than the nominal bulk composition of the alloys suggested. Sn enrichment at the metal/external oxide interface was reduced compared to the free surface and decreased with increasing bulk Mn content, which was attributed to changes in the external oxide morphology and metal/internal oxide interfaces acting as Sn sinks. Full article

(This article belongs to the Section Metals and Alloys)

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14 pages, 2024 KiB

Open AccessEditor’s ChoiceArticle

On Crossover Temperatures of Viscous Flow Related to Structural Rearrangements in Liquids

by Michael I. Ojovan and Dmitri V. Louzguine-Luzgin

Materials 2024, 17(6), 1261; https://doi.org/10.3390/ma17061261 - 8 Mar 2024

Cited by 4 | Viewed by 930

Abstract

An additional crossover of viscous flow in liquids occurs at a temperature T_vm above the known non-Arrhenius to Arrhenius crossover temperature (T_A). T_vm is the temperature when the minimum possible viscosity value η_min is attained, and the [...] Read more.

An additional crossover of viscous flow in liquids occurs at a temperature T_vm above the known non-Arrhenius to Arrhenius crossover temperature (T_A). T_vm is the temperature when the minimum possible viscosity value η_min is attained, and the flow becomes non-activated with a further increase in temperature. Explicit equations are proposed for the assessments of both T_vm and η_min, which are shown to provide data that are close to those experimentally measured. Numerical estimations reveal that the new crossover temperature is very high and can barely be achieved in practical uses, although at temperatures close to it, the contribution of the non-activated regime of the flow can be accounted for. Full article

(This article belongs to the Special Issue Innovations in Modelling and Simulations: Bridging Microstructures to Macroscopic Properties in Advanced Materials)

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11 pages, 2286 KiB

Open AccessEditor’s ChoiceArticle

Comparison of the Intensity of Biofilm Production by Oral Microflora and Its Adhesion on the Surface of Zirconia Produced in Additive and Subtractive Technology: An In Vitro Study

by Wojciech Frąckiewicz, Agata Pruss, Marcin Królikowski, Paweł Szymlet and Ewa Sobolewska

Materials 2024, 17(6), 1231; https://doi.org/10.3390/ma17061231 - 7 Mar 2024

Viewed by 971

Abstract

Background: This in vitro study set out to find out how well oral cavity-dwelling bacteria can form biofilms and adhere on the surfaces of zirconium oxide samples created by 3D printing and milling technologies. Methods: 5 strains of microorganisms were used for the [...] Read more.

Background: This in vitro study set out to find out how well oral cavity-dwelling bacteria can form biofilms and adhere on the surfaces of zirconium oxide samples created by 3D printing and milling technologies. Methods: 5 strains of microorganisms were used for the study, and 40 zirconium oxide samples were prepared, which were divided into two groups (n = 20)—20 samples produced using removal technology comprised the control group, while 20 samples produced by 3D printing technology comprised the test group. The prepared samples were placed in culture media of bacteria and fungi that naturally occur in the oral cavity. Then, the intensity of biofilm build-up on the samples was determined using qualitative and quantitative methods. The results for both materials were compared with each other. Results: No variations in the degree of biofilm deposition on zirconium oxide samples were found for the microorganisms Streptococcus mutans, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus. For Candida albicans fungi, more intense biofilm deposition was observed on samples made using 3D printing technology, but these differences were not statistically significant. Conclusion: The biofilm accumulation intensity of ceramics produced by additive technology is comparable to that of milled zirconium oxide, which supports the material’s broader use in clinical practice from a microbiological perspective. This ceramic has demonstrated its ability to compete with zirconium oxide produced by milling techniques in in vitro experiments, but sadly, no in vivo tests have yet been found to determine how this material will function in a patient’s oral cavity. Full article

(This article belongs to the Section Biomaterials)

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12 pages, 4516 KiB

Open AccessEditor’s ChoiceArticle

Preparation of CS-LS/AgNPs Composites and Photocatalytic Degradation of Dyes

by Jiabao Wu, Xinpeng Chen, Aijing Li, Tieling Xing and Guoqiang Chen

Materials 2024, 17(5), 1214; https://doi.org/10.3390/ma17051214 - 6 Mar 2024

Viewed by 1321

Abstract

Synthetic dyes are prone to water pollution during use, jeopardizing biodiversity and human health. This study aimed to investigate the adsorption and photocatalytic assist potential of sodium lignosulfonate (LS) in in situ reduced silver nanoparticles (AgNPs) and chitosan (CS)-loaded silver nanoparticles (CS-LS/AgNPs) as [...] Read more.

Synthetic dyes are prone to water pollution during use, jeopardizing biodiversity and human health. This study aimed to investigate the adsorption and photocatalytic assist potential of sodium lignosulfonate (LS) in in situ reduced silver nanoparticles (AgNPs) and chitosan (CS)-loaded silver nanoparticles (CS-LS/AgNPs) as adsorbents for Rhodamine B (RhB). The AgNPs were synthesized by doping LS on the surface of chitosan for modification. Fourier transform infrared (FT-IR) spectrometry, energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to confirm the synthesis of nanomaterials. The adsorption and photocatalytic removal experiments of RhB were carried out under optimal conditions (initial dye concentration of 20 mg/L, adsorbent dosage of 0.02 g, time of 60 min, and UV power of 250 W), and the kinetics of dye degradation was also investigated, which showed that the removal rate of RhB by AgNPs photocatalysis can reach 55%. The results indicated that LS was highly effective as a reducing agent for the large-scale production of metal nanoparticles and can be used for dye decolorization. This work provides a new catalyst for the effective removal of dye from wastewater, and can achieve high-value applications of chitosan and lignin. Full article

(This article belongs to the Special Issue Properties and Applications of Advanced Textile Materials)

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20 pages, 7712 KiB

Open AccessEditor’s ChoiceArticle

The Influence of the Shielding-Gas Flow Rate on the Mechanical Properties of TIG-Welded Butt Joints of Commercially Pure Grade 1 Titanium

by Krzysztof Szwajka, Joanna Zielińska-Szwajka and Tomasz Trzepieciński

Materials 2024, 17(5), 1217; https://doi.org/10.3390/ma17051217 - 6 Mar 2024

Viewed by 1220

Abstract

This article proposes as a novelty the differentiation of shielding-gas flow rates from both sides of the tungsten inert gas (TIG)-welded butt joints of commercially pure (CP) grade 1 titanium tubes. Such an approach is aimed at economically reducing the amount of protective [...] Read more.

This article proposes as a novelty the differentiation of shielding-gas flow rates from both sides of the tungsten inert gas (TIG)-welded butt joints of commercially pure (CP) grade 1 titanium tubes. Such an approach is aimed at economically reducing the amount of protective gas used in TIG closed butt welding. The effect of the shielding-gas flow rate on the properties of CP grade 1 titanium butt-welded joints made using the tungsten inert gas (TIG)-welding method. Butt-welded joints were made for different values of the shielding-gas flow from the side of the root of the weld. Argon 5.0 was used as the shielding gas in the welding process. As part of the research, the welded joints obtained were analysed using optical and scanning electron microscopy. The microstructural characteristics of the joints were examined using an optical microscope, and the mechanical properties were determined using hardness and tensile tests. It was observed that as the flow of the shielding gas decreases, the hardness of the weld material increases and its brittleness also increases. A similar trend related to the amount of gas flow was also noticeable for the tensile strength of the joints. The increase in the hardness of the weld and the heat-affected zone compared to the base metal is mainly related to the increase in the amount of acicular structure (α′ phase). The optimal gas flow rates from the side of the root of weld were found at the values of 12 dm³/min. Full article

(This article belongs to the Special Issue Advances in Welding Techniques, Welding Inspection, and Welding Testing Methods)

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26 pages, 5515 KiB

Open AccessEditor’s ChoiceArticle

Marble Powder as a Soil Stabilizer: An Experimental Investigation of the Geotechnical Properties and Unconfined Compressive Strength Analysis

by Ibrahim Haruna Umar and Hang Lin

Materials 2024, 17(5), 1208; https://doi.org/10.3390/ma17051208 - 5 Mar 2024

Cited by 7 | Viewed by 2377

Abstract

Fine-grained soils present engineering challenges. Stabilization with marble powder has shown promise for improving engineering properties. Understanding the temporal evolution of Unconfined Compressive Strength (UCS) and geotechnical properties in stabilized soils could aid strength assessment. This study investigates the stabilization of fine-grained clayey [...] Read more.

Fine-grained soils present engineering challenges. Stabilization with marble powder has shown promise for improving engineering properties. Understanding the temporal evolution of Unconfined Compressive Strength (UCS) and geotechnical properties in stabilized soils could aid strength assessment. This study investigates the stabilization of fine-grained clayey soils using waste marble powder as an alternative binder. Laboratory experiments were conducted to evaluate the geotechnical properties of soil–marble powder mixtures, including Atterberg’s limits, compaction characteristics, California Bearing Ratio (CBR), Indirect Tensile Strength (ITS), and Unconfined Compressive Strength (UCS). The effects of various factors, such as curing time, molding water content, and composition ratios, on UCS, were analyzed using Exploratory Data Analysis (EDA) techniques, including histograms, box plots, and statistical modeling. The results show that the CBR increased from 10.43 to 22.94% for unsoaked and 4.68 to 12.46% for soaked conditions with 60% marble powder, ITS rose from 100 to 208 kN/m² with 60–75% marble powder, and UCS rose from 170 to 661 kN/m² after 28 days of curing, molding water content (optimum at 22.5%), and composition ratios (optimum at 60% marble powder). Complex modeling yielded R² (0.954) and RMSE (29.82 kN/m²) between predicted and experimental values. This study demonstrates the potential of utilizing waste marble powder as a sustainable and cost-effective binder for soil stabilization, transforming weak soils into viable construction materials. Full article

(This article belongs to the Special Issue Reliability Modeling of Complex Systems in Materials and Devices)

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19 pages, 3982 KiB

Open AccessEditor’s ChoiceArticle

Investigation and Validation of a Shape Memory Alloy Material Model Using Interactive Fibre Rubber Composites

by Achyuth Ram Annadata, Aline Iobana Acevedo-Velazquez, Lucas A. Woodworth, Thomas Gereke, Michael Kaliske, Klaus Röbenack and Chokri Cherif

Materials 2024, 17(5), 1163; https://doi.org/10.3390/ma17051163 - 1 Mar 2024

Cited by 1 | Viewed by 1268

Abstract

The growing demand for intelligent systems with improved human-machine interactions has created an opportunity to develop adaptive bending structures. Interactive fibre rubber composites (IFRCs) are created using smart materials as actuators to obtain any desired application using fibre-reinforced elastomer. Shape memory alloys (SMAs) [...] Read more.

The growing demand for intelligent systems with improved human-machine interactions has created an opportunity to develop adaptive bending structures. Interactive fibre rubber composites (IFRCs) are created using smart materials as actuators to obtain any desired application using fibre-reinforced elastomer. Shape memory alloys (SMAs) play a prominent role in the smart material family and are being used for various applications. Their diverse applications are intended for commercial and research purposes, and the need to model and analyse these application-based structures to achieve their maximum potential is of utmost importance. Many material models have been developed to characterise the behaviour of SMAs. However, there are very few commercially developed finite element models that can predict their behaviour. One such model is the Souza and Auricchio (SA) SMA material model incorporated in ANSYS, with the ability to solve for both shape memory effect (SME) and superelasticity (SE) but with a limitation of considering pre-stretch for irregularly shaped geometries. In order to address this gap, Woodworth and Kaliske (WK) developed a phenomenological constitutive SMA material model, offering the flexibility to apply pre-stretches for SMA wires with irregular profiles. This study investigates the WK SMA material model, utilizing deformations observed in IFRC structures as a reference and validating them against simulated models using the SA SMA material model. This validation process is crucial in ensuring the reliability and accuracy of the WK model, thus enhancing confidence in its application for predictive analysis in SMA-based systems. Full article

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

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22 pages, 4276 KiB

Open AccessEditor’s ChoiceArticle

Silver Nanoparticles-Chitosan Nanocomposites: A Comparative Study Regarding Different Chemical Syntheses Procedures and Their Antibacterial Effect

by Dan Chicea, Alexandra Nicolae-Maranciuc and Liana-Maria Chicea

Materials 2024, 17(5), 1113; https://doi.org/10.3390/ma17051113 - 28 Feb 2024

Cited by 4 | Viewed by 1170

Abstract

Nanocomposites based on silver nanoparticles and chitosan present important advantages for medical applications, showing over time their role in antibacterial evaluation. This work presents the comparative study of two chemical synthesis procedures of nanocomposites, based on trisodium citrate dihydrate and sodium hydroxide, using [...] Read more.

Nanocomposites based on silver nanoparticles and chitosan present important advantages for medical applications, showing over time their role in antibacterial evaluation. This work presents the comparative study of two chemical synthesis procedures of nanocomposites, based on trisodium citrate dihydrate and sodium hydroxide, using various chitosan concentrations for a complex investigation. The nanocomposites were characterized by AFM and DLS regarding their dimensions, while FT-IR and UV–VIS spectrometry were used for the optical properties and to reveal the binding of silver nanoparticles with chitosan. Their antibacterial effect was determined using a disk diffusion method on two bacteria strains, E. coli and S. aureus. The results indicate that, when using both methods, the nanocomposites obtained were below 100 nm, yet the antibacterial effect proved to be stronger for the nanocomposites obtained using sodium hydroxide. Furthermore, the antibacterial effect can be related to the nanocomposites’ sizes, since the smallest dimension nanocomposites exhibited the best bacterial growth inhibition on both bacteria strains we tested and for both types of silver nanocomposites. Full article

(This article belongs to the Special Issue Nanocomposite Based Materials for Various Applications)

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45 pages, 11151 KiB

Open AccessEditor’s ChoiceReview

Evaluation of the Embrittlement in Reactor Pressure-Vessel Steels Using a Hybrid Nondestructive Electromagnetic Testing and Evaluation Approach

by Gábor Vértesy, Madalina Rabung, Antal Gasparics, Inge Uytdenhouwen, James Griffin, Daniel Algernon, Sonja Grönroos and Jari Rinta-Aho

Materials 2024, 17(5), 1106; https://doi.org/10.3390/ma17051106 - 28 Feb 2024

Cited by 1 | Viewed by 1388

Abstract

The nondestructive determination of the neutron-irradiation-induced embrittlement of nuclear reactor pressure-vessel steel is a very important and recent problem. Within the scope of the so-called NOMAD project funded by the Euratom research and training program, novel nondestructive electromagnetic testing and evaluation (NDE) methods [...] Read more.

The nondestructive determination of the neutron-irradiation-induced embrittlement of nuclear reactor pressure-vessel steel is a very important and recent problem. Within the scope of the so-called NOMAD project funded by the Euratom research and training program, novel nondestructive electromagnetic testing and evaluation (NDE) methods were applied to the inspection of irradiated reactor pressure-vessel steel. In this review, the most important results of this project are summarized. Different methods were used and compared with each other. The measurement results were compared with the destructively determined ductile-to-brittle transition temperature (DBTT) values. Three magnetic methods, 3MA (micromagnetic, multiparameter, microstructure and stress analysis), MAT (magnetic adaptive testing), and Barkhausen noise technique (MBN), were found to be the most promising techniques. The results of these methods were in good agreement with each other. A good correlation was found between the magnetic parameters and the DBTT values. The basic idea of the NOMAD project is to use a multi-method/multi-parameter approach and to focus on the synergies that allow us to recognize the side effects, therefore suppressing them at the same time. Different types of machine-learning (ML) algorithms were tested in a competitive manner, and their performances were evaluated. The important outcome of the ML technique is that not only one but several different ML techniques could reach the required precision and reliability, i.e., keeping the DBTT prediction error lower than a ±25 °C threshold, which was previously not possible for any of the NDE methods as single entities. A calibration/training procedure was carried out on the merged outcome of the testing methods with excellent results to predict the transition temperature, yield strength, and mechanical hardness for all investigated materials. Our results, achieved within the NOMAD project, can be useful for the future potential introduction of this (and, in general, any) nondestructive evolution method. Full article

(This article belongs to the Section Materials Physics)

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16 pages, 8052 KiB

Open AccessEditor’s ChoiceArticle

Analysis of the Effect of an Open Hole on the Buckling of a Compressed Composite Plate

by Pawel Wysmulski

Materials 2024, 17(5), 1081; https://doi.org/10.3390/ma17051081 - 27 Feb 2024

Cited by 4 | Viewed by 1142

Abstract

This paper investigates the effect of an open hole on the stability of a compressed laminated composite plate. The study was carried out in two ways: using experimental tests and numerical analysis. As a result of the experiment, the buckling form and path [...] Read more.

This paper investigates the effect of an open hole on the stability of a compressed laminated composite plate. The study was carried out in two ways: using experimental tests and numerical analysis. As a result of the experiment, the buckling form and path of the plate were recorded. The form of buckling was determined using the ARAMIS non-contact measurement system. The critical load value was determined from the working path using the approximation method. The experimental results were verified by numerical analysis based on the finite element method. FEM investigations were carried out in terms of a linear eigenproblem analysis. This allowed the bifurcation load and the corresponding buckling form of the numerical model of the plate to be determined. Investigating the effect of the hole in the compressed plate at a critical state showed high agreement between the proposed test methods. No clear effect of the hole size on the buckling of the plate was observed. In contrast, a clear effect of the hole on the critical load value was determined. The maximum decrease in the critical load value was 14%. The same decrease was observed for the stiffness of the post-critical characteristics. It was shown that the [45|−45|90|0]s composite plate had more than three times lower strength compared to [0|−45|45|90]s and [0|90|0|90]s. The novelty of this article is the development of a research methodology based on new interdisciplinary research methods for describing the influence of the central hole on the stability of compressed composite plates. The ABAQUS system was used for the numerical analysis. Full article

(This article belongs to the Section Advanced Composites)

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24 pages, 9586 KiB

Open AccessEditor’s ChoiceArticle

The Development of Sustainable Polyethylene Terephthalate Glycol-Based (PETG) Blends for Additive Manufacturing Processing—The Use of Multilayered Foil Waste as the Blend Component

by Mikołaj Garwacki, Igor Cudnik, Damian Dziadowiec, Piotr Szymczak and Jacek Andrzejewski

Materials 2024, 17(5), 1083; https://doi.org/10.3390/ma17051083 - 27 Feb 2024

Cited by 3 | Viewed by 2044

Abstract

The polymer foil industry is one of the leading producers of plastic waste. The development of new recycling methods for packaging products is one of the biggest demands in today’s engineering. The subject of this research was the melt processing of multilayered PET-based [...] Read more.

The polymer foil industry is one of the leading producers of plastic waste. The development of new recycling methods for packaging products is one of the biggest demands in today’s engineering. The subject of this research was the melt processing of multilayered PET-based foil waste with PETG copolymer. The resulting blends were intended for additive manufacturing processing using the fused deposition modeling (FDM) method. In order to improve the properties of the developed materials, the blends compounding procedure was conducted with the addition of a reactive chain extender (CE) and elastomeric copolymer used as an impact modifier (IM). The samples were manufactured using the 3D printing technique and, for comparison, using the traditional injection molding method. The obtained samples were subjected to a detailed characterization procedure, including mechanical performance evaluation, thermal analysis, and rheological measurements. This research confirms that PET-based film waste can be successfully used for the production of filament, and for most samples, the FDM printing process can be conducted without any difficulties. Unfortunately, the unmodified blends are characterized by brittleness, which makes it necessary to use an elastomer additive (IM). The presence of a semicrystalline PET phase improves the thermal resistance of the prepared blends; however, an annealing procedure is required for this purpose. Full article

(This article belongs to the Special Issue Polymers: From Waste to Potential Reuse)

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32 pages, 5942 KiB

Open AccessEditor’s ChoiceArticle

An Extended Kolmogorov–Avrami–Ishibashi (EKAI) Model to Simulate Dynamic Characteristics of Polycrystalline-Ferroelectric-Gate Field-Effect Transistors

by Shigeki Sakai and Mitsue Takahashi

Materials 2024, 17(5), 1077; https://doi.org/10.3390/ma17051077 - 26 Feb 2024

Viewed by 2053

Abstract

A physics-based model on polarization switching in ferroelectric polycrystalline films is proposed. The calculation results by the model agree well with experimental results regarding dynamic operations of ferroelectric-gate field-effect transistors (FeFETs). In the model, an angle θ for each grain in the ferroelectric [...] Read more.

A physics-based model on polarization switching in ferroelectric polycrystalline films is proposed. The calculation results by the model agree well with experimental results regarding dynamic operations of ferroelectric-gate field-effect transistors (FeFETs). In the model, an angle θ for each grain in the ferroelectric polycrystal is defined, where θ is the angle between the spontaneous polarization and the film normal direction. Under a constant electric field for a single-crystal film with θ = 0, phenomena regarding polarization domain nucleation and wall propagation are well described by the Kolmogorov–Avrami–Ishibashi theory. Since the electric fields are time-dependent in FeFET operations and the θ values are distributed in the polycrystalline film, the model in this paper forms an extended Kolmogorov–Avrami–Ishibashi (EKAI) model. Under a low electric field, the nucleation and domain propagation proceed according to thermally activated processes, meaning that switching the time scale of a grain with the angle θ is proportional to an exponential form as

e x p (c o n s t . / E_{z} c o s θ)

[

E_{z}

: the film-normal electric field]. Wide θ distribution makes the time response quite broad even on the logarithmic scale, which relates well with the broad switching time experimentally shown by FeFETs. The EKAI model is physics based and need not assume non-physical distribution functions in it. Full article

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

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20 pages, 11077 KiB

Open AccessEditor’s ChoiceArticle

Experimental and Theoretical Investigation on Heat Transfer Enhancement in Micro Scale Using Helical Connectors

by Malyne Abraham, Zachary Abboud, Gabriel Herrera Arriaga, Kendall Tom, Samuel Austin and Saeid Vafaei

Materials 2024, 17(5), 1067; https://doi.org/10.3390/ma17051067 - 26 Feb 2024

Cited by 1 | Viewed by 1074

Abstract

Microscale electronics have become increasingly more powerful, requiring more efficient cooling systems to manage the higher thermal loads. To meet this need, current research has been focused on overcoming the inefficiencies present in typical thermal management systems due to low Reynolds numbers within [...] Read more.

Microscale electronics have become increasingly more powerful, requiring more efficient cooling systems to manage the higher thermal loads. To meet this need, current research has been focused on overcoming the inefficiencies present in typical thermal management systems due to low Reynolds numbers within microchannels and poor physical properties of the working fluids. For the first time, this research investigated the effects of a connector with helical geometry on the heat transfer coefficient at low Reynolds numbers. The introduction of a helical connector at the inlet of a microchannel has been experimentally tested and results have shown that this approach to flow augmentation has a great potential to increase the heat transfer capabilities of the working fluid, even at low Reynolds numbers. In general, a helical connector can act as a stabilizer or a mixer, based on the characteristics of the connector for the given conditions. When the helical connector acts as a mixer, secondary flows develop that increase the random motion of molecules and possible nanoparticles, leading to an enhancement in the heat transfer coefficient in the microchannel. Otherwise, the heat transfer coefficient decreases. It is widely known that introducing nanoparticles into the working fluids has the potential to increase the thermal conductivity of the base fluid, positively impacting the heat transfer coefficient; however, viscosity also tends to increase, reducing the random motion of molecules and ultimately reducing the heat transfer capabilities of the working fluid. Therefore, optimizing the effects of nanoparticles characteristics while reducing viscous effects is essential. In this study, deionized water and deionized water–diamond nanofluid at 0.1 wt% were tested in a two-microchannel system fitted with a helical connector in between. It was found that the helical connector can make a great heat transfer coefficient enhancement in low Reynolds numbers when characteristics of geometry are optimized for given conditions. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

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22 pages, 5497 KiB

Open AccessEditor’s ChoiceArticle

Synergistic Effects of Co₃O₄-gC₃N₄-Coated ZnO Nanoparticles: A Novel Approach for Enhanced Photocatalytic Degradation of Ciprofloxacin and Hydrogen Evolution via Water Splitting

by Abniel Machín, Carmen Morant, Loraine Soto-Vázquez, Edgard Resto, José Ducongé, María Cotto, Pedro J. Berríos-Rolón, Cristian Martínez-Perales and Francisco Márquez

Materials 2024, 17(5), 1059; https://doi.org/10.3390/ma17051059 - 25 Feb 2024

Cited by 3 | Viewed by 1774

Abstract

This research evaluates the efficacy of catalysts based on Co₃O₄-gC₃N₄@ZnONPs in the degradation of ciprofloxacin (CFX) and the photocatalytic production of H₂ through water splitting. The results show that CFX experiences prompt photodegradation, with [...] Read more.

This research evaluates the efficacy of catalysts based on Co₃O₄-gC₃N₄@ZnONPs in the degradation of ciprofloxacin (CFX) and the photocatalytic production of H₂ through water splitting. The results show that CFX experiences prompt photodegradation, with rates reaching up to 99% within 60 min. Notably, the 5% (Co₃O₄-gC₃N₄)@ZnONPs emerged as the most potent catalyst. The recyclability studies of the catalyst revealed a minimal activity loss, approximately 6%, after 15 usage cycles. Using gas chromatography–mass spectrometry (GC-MS) techniques, the by-products of CFX photodegradation were identified, which enabled the determination of the potential degradation pathway and its resultant products. Comprehensive assessments involving photoluminescence, bandgap evaluations, and the study of scavenger reactions revealed a degradation mechanism driven primarily by superoxide radicals. Moreover, the catalysts demonstrated robust performance in H₂ photocatalytic production, with some achieving outputs as high as 1407 µmol/hg in the visible spectrum (around 500 nm). Such findings underline the potential of these materials in environmental endeavors, targeting both water purification from organic pollutants and energy applications. Full article

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

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20 pages, 6220 KiB

Open AccessEditor’s ChoiceArticle

The Beneficial Impact of Mineral Content in Spent-Coffee-Ground-Derived Hard Carbon on Sodium-Ion Storage

by Sonya Harizanova, Ivan Uzunov, Lyubomir Aleksandrov, Maria Shipochka, Ivanka Spassova and Mariya Kalapsazova

Materials 2024, 17(5), 1016; https://doi.org/10.3390/ma17051016 - 22 Feb 2024

Cited by 2 | Viewed by 1735

Abstract

The key technological implementation of sodium-ion batteries is converting biomass-derived hard carbons into effective anode materials. This becomes feasible if appropriate knowledge of the relations between the structure of carbonized biomass products, the mineral ash content in them, and Na storage properties is [...] Read more.

The key technological implementation of sodium-ion batteries is converting biomass-derived hard carbons into effective anode materials. This becomes feasible if appropriate knowledge of the relations between the structure of carbonized biomass products, the mineral ash content in them, and Na storage properties is gained. In this study, we examine the simultaneous impact of the ash phase composition and carbon structure on the Na storage properties of hard carbons derived from spent coffee grounds (SCGs). The carbon structure is modified using the pre-carbonization of SCGs at 750 °C, followed by annealing at 1100 °C in an Ar atmosphere. Two variants of the pre-carbonization procedure are adopted: the pre-carbonization of SCGs in a fixed bed and CO₂ flow. For the sake of comparison, the pre-carbonized products are chemically treated to remove the ash content. The Na storage performance of SCG-derived carbons is examined in model two and three Na-ion cells. It was found that ash-containing carbons outperformed the ash-free analogs with respect to cycling stability, Coulombic efficiency, and rate capability. The enhanced performance is explained in terms of the modification of the carbon surface by ash phases (mainly albite) and its interaction with the electrolyte, which is monitored by ex situ XPS. Full article

(This article belongs to the Special Issue Size-Dependent Effects in Materials for Environmental Protection and Energy Application)

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44 pages, 14513 KiB

Open AccessEditor’s ChoiceReview

Hydrogen Impact: A Review on Diffusibility, Embrittlement Mechanisms, and Characterization

by Qidong Li, Hesamedin Ghadiani, Vahid Jalilvand, Tahrim Alam, Zoheir Farhat and Md. Aminul Islam

Materials 2024, 17(4), 965; https://doi.org/10.3390/ma17040965 - 19 Feb 2024

Cited by 12 | Viewed by 6710

Abstract

Hydrogen embrittlement (HE) is a broadly recognized phenomenon in metallic materials. If not well understood and managed, HE may lead to catastrophic environmental failures in vessels containing hydrogen, such as pipelines and storage tanks. HE can affect the mechanical properties of materials such [...] Read more.

Hydrogen embrittlement (HE) is a broadly recognized phenomenon in metallic materials. If not well understood and managed, HE may lead to catastrophic environmental failures in vessels containing hydrogen, such as pipelines and storage tanks. HE can affect the mechanical properties of materials such as ductility, toughness, and strength, mainly through the interaction between metal defects and hydrogen. Various phenomena such as hydrogen adsorption, hydrogen diffusion, and hydrogen interactions with intrinsic trapping sites like dislocations, voids, grain boundaries, and oxide/matrix interfaces are involved in this process. It is important to understand HE mechanisms to develop effective hydrogen resistant strategies. Tensile, double cantilever beam, bent beam, and fatigue tests are among the most common techniques employed to study HE. This article reviews hydrogen diffusion behavior, mechanisms, and characterization techniques. Full article

(This article belongs to the Special Issue Corrosion and Mechanical Behavior of Metal Materials (2nd Edition))

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35 pages, 16769 KiB

Open AccessEditor’s ChoiceReview

2D Materials Nanoarchitectonics for 3D Structures/Functions

by Katsuhiko Ariga

Materials 2024, 17(4), 936; https://doi.org/10.3390/ma17040936 - 17 Feb 2024

Viewed by 2919

Abstract

It has become clear that superior material functions are derived from precisely controlled nanostructures. This has been greatly accelerated by the development of nanotechnology. The next step is to assemble materials with knowledge of their nano-level structures. This task is assigned to the [...] Read more.

It has become clear that superior material functions are derived from precisely controlled nanostructures. This has been greatly accelerated by the development of nanotechnology. The next step is to assemble materials with knowledge of their nano-level structures. This task is assigned to the post-nanotechnology concept of nanoarchitectonics. However, nanoarchitectonics, which creates intricate three-dimensional functional structures, is not always easy. Two-dimensional nanoarchitectonics based on reactions and arrangements at the surface may be an easier target to tackle. A better methodology would be to define a two-dimensional structure and then develop it into a three-dimensional structure and function. According to these backgrounds, this review paper is organized as follows. The introduction is followed by a summary of the three issues; (i) 2D to 3D dynamic structure control: liquid crystal commanded by the surface, (ii) 2D to 3D rational construction: a metal–organic framework (MOF) and a covalent organic framework (COF); (iii) 2D to 3D functional amplification: cells regulated by the surface. In addition, this review summarizes the important aspects of the ultimate three-dimensional nanoarchitectonics as a perspective. The goal of this paper is to establish an integrated concept of functional material creation by reconsidering various reported cases from the viewpoint of nanoarchitectonics, where nanoarchitectonics can be regarded as a method for everything in materials science. Full article

(This article belongs to the Special Issue Materials Nanoarchitectonics for Membranes, Surfaces, Self-Assembly, and Biomimetics)

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16 pages, 4129 KiB

Open AccessEditor’s ChoiceArticle

Resonant Tunnelling and Intersubband Optical Properties of ZnO/ZnMgO Semiconductor Heterostructures: Impact of Doping and Layer Structure Variation

by Aleksandar Atić, Xizhe Wang, Nikola Vuković, Novak Stanojević, Aleksandar Demić, Dragan Indjin and Jelena Radovanović

Materials 2024, 17(4), 927; https://doi.org/10.3390/ma17040927 - 17 Feb 2024

Cited by 1 | Viewed by 1204

Abstract

ZnO-based heterostructures are up-and-coming candidates for terahertz (THz) optoelectronic devices, largely owing to their innate material attributes. The significant ZnO LO-phonon energy plays a pivotal role in mitigating thermally induced LO-phonon scattering, potentially significantly elevating the temperature performance of quantum cascade lasers (QCLs). [...] Read more.

ZnO-based heterostructures are up-and-coming candidates for terahertz (THz) optoelectronic devices, largely owing to their innate material attributes. The significant ZnO LO-phonon energy plays a pivotal role in mitigating thermally induced LO-phonon scattering, potentially significantly elevating the temperature performance of quantum cascade lasers (QCLs). In this work, we calculate the electronic structure and absorption of ZnO/ZnMgO multiple semiconductor quantum wells (MQWs) and the current density–voltage characteristics of nonpolar m-plane ZnO/ZnMgO double-barrier resonant tunnelling diodes (RTDs). Both MQWs and RTDs are considered here as two building blocks of a QCL. We show how the doping, Mg percentage and layer thickness affect the absorption of MQWs at room temperature. We confirm that in the high doping concentrations regime, a full quantum treatment that includes the depolarisation shift effect must be considered, as it shifts mid-infrared absorption peak energy for several tens of meV. Furthermore, we also focus on the performance of RTDs for various parameter changes and conclude that, to maximise the peak-to-valley ratio (PVR), the optimal doping density of the analysed ZnO/Zn₈₈Mg₁₂O double-barrier RTD should be approximately

10^{18} {c m}^{- 3}

, whilst the optimal barrier thickness should be 1.3 nm, with a Mg mole fraction of ~9%. Full article

(This article belongs to the Special Issue Special Edition on Semiconductor Materials and Optics)

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11 pages, 8460 KiB

Open AccessEditor’s ChoiceArticle

Development of Antibacterial Resin Composites Incorporating Poly(METAC) Clusters

by Tomoki Kohno, Haruaki Kitagawa, Ririko Tsuboi, Fan Deng, Hirohiko Sakai, Tingyi Wu, Yo-Shiuan Fan, Linghao Xiao and Satoshi Imazato

Materials 2024, 17(4), 896; https://doi.org/10.3390/ma17040896 - 15 Feb 2024

Viewed by 1432

Abstract

This study examined the antibacterial effects and physical properties of a novel resin composite incorporating poly[{2-(methacryloyloxy)ethyl}trimethylammonium chloride] (poly(METAC)), a methacrylate cationic polymer comprising quaternary ammonium compounds (QACs). Resin composites incorporating poly(METAC) were fabricated by adding 6 wt.% METAC aqueous solution to a commercially [...] Read more.

This study examined the antibacterial effects and physical properties of a novel resin composite incorporating poly[{2-(methacryloyloxy)ethyl}trimethylammonium chloride] (poly(METAC)), a methacrylate cationic polymer comprising quaternary ammonium compounds (QACs). Resin composites incorporating poly(METAC) were fabricated by adding 6 wt.% METAC aqueous solution to a commercially available resin composite. The FE-SEM/EDS and Raman spec-troscopy analyses showed that METAC was assembled and polymerized in the resin composites after curing. The antibacterial effect was evaluated by inoculating Streptococcus mutans or Strepto-coccus sobrinus suspensions on the surface of cured resin composites, and the experimental resin composites incorporating poly(METAC) clusters exhibited bactericidal effects even after 28 days of ageing. The physical properties of the experimental resin composites were within the ISO-stipulated ranges. Newly fabricated resin composites containing the QAC-based poly(METAC) cluster ex-hibited long-term bactericidal effects against oral bacteria on their surfaces and demonstrated ac-ceptable physical properties for clinical use. Full article

(This article belongs to the Special Issue Novel Dental Restorative Materials (Volume II))

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12 pages, 3039 KiB

Open AccessEditor’s ChoiceArticle

Atomic-Scale Structural Properties in NiCo₂O₄/CuFe₂O₄ Bilayer Heterostructures on (001)-MgAl₂O₄ Substrate Regulated by Film Thickness

by Kun Liu, Ruyi Zhang, Jiankang Li and Songyou Zhang

Materials 2024, 17(4), 871; https://doi.org/10.3390/ma17040871 - 13 Feb 2024

Cited by 2 | Viewed by 940

Abstract

Changing film thickness to manipulate microstructural properties has been considered as a potential method in practical application. Here, we report that atomic-scale structural properties are regulated by film thickness in an NiC_O2O₄(NCO)/CuFe₂O₄(CFO) bilayer heterostructure prepared [...] Read more.

Changing film thickness to manipulate microstructural properties has been considered as a potential method in practical application. Here, we report that atomic-scale structural properties are regulated by film thickness in an NiC_O2O₄(NCO)/CuFe₂O₄(CFO) bilayer heterostructure prepared on (001)-MgAl₂O₄ (MAO) substrate by means of aberration-corrected scanning transmission electron microscopy (STEM). The misfit dislocations at the NCO/CFO interface and antiphase boundaries (APBs) bound to dislocations within the films are both found in NCO (40 nm)/CFO (40 nm)/MAO heterostructures, contributing to the relaxation of mismatch lattice strain. In addition, the non-overlapping a/4[101]-APB is found and the structural transformation of this kind of APB is resolved at the atomic scale. In contrast, only the interfacial dislocations form at the interface without the formation of APBs within the films in NCO (10 nm)/CFO (40 nm)/MAO heterostructures. Our results provide evidence that the formation of microstructural defects can be regulated by changing film thickness to tune the magnetic properties of epitaxial bilayer spinel oxide films. Full article

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

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13 pages, 3072 KiB

Open AccessEditor’s ChoiceArticle

Fabrication and Characterization of an Electrochemical Platform for Formaldehyde Oxidation, Based on Glassy Carbon Modified with Multi-Walled Carbon Nanotubes and Electrochemically Generated Palladium Nanoparticles

by Andrzej Leniart, Barbara Burnat, Mariola Brycht, Maryia-Mazhena Dzemidovich and Sławomira Skrzypek

Materials 2024, 17(4), 841; https://doi.org/10.3390/ma17040841 - 9 Feb 2024

Cited by 1 | Viewed by 1391

Abstract

This study outlines the fabrication process of an electrochemical platform utilizing glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and palladium nanoparticles (PdNPs). The MWCNTs were applied on the GCE surface using the drop-casting method and PdNPs were produced electrochemically by [...] Read more.

This study outlines the fabrication process of an electrochemical platform utilizing glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and palladium nanoparticles (PdNPs). The MWCNTs were applied on the GCE surface using the drop-casting method and PdNPs were produced electrochemically by a potentiostatic method employing various programmed charges from an ammonium tetrachloropalladate(II) solution. The resulting GCEs modified with MWCNTs and PdNPs underwent comprehensive characterization for topographical and morphological attributes, utilizing atomic force microscopy and scanning electron microscopy along with energy-dispersive X-ray spectrometry. Electrochemical assessment of the GCE/MWCNTs/PdNPs involved cyclic voltammetry (CV) and electrochemical impedance spectroscopy conducted in perchloric acid solution. The findings revealed even dispersion of PdNPs, and depending on the electrodeposition parameters, PdNPs were produced within four size ranges, i.e., 10–30 nm, 20–40 nm, 50–60 nm, and 70–90 nm. Additionally, the electrocatalytic activity toward formaldehyde oxidation was assessed through CV. It was observed that an increase in the size of the PdNPs corresponded to enhanced catalytic activity in the formaldehyde oxidation reaction on the GCE/MWCNTs/PdNPs. Furthermore, satisfactory long-term stability over a period of 42 days was noticed for the GCE/MWCNTs/PDNPs(100) material which demonstrated the best electrocatalytic properties in the electrooxidation reaction of formaldehyde. Full article

(This article belongs to the Special Issue Advanced Electrode Materials Dedicated for Electroanalysis)

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16 pages, 5925 KiB

Open AccessEditor’s ChoiceArticle

Microstructure and Mechanical Properties of Ti-6Al-4V Welds Produced with Different Processes

by Sakari Tolvanen, Robert Pederson and Uta Klement

Materials 2024, 17(4), 782; https://doi.org/10.3390/ma17040782 - 6 Feb 2024

Cited by 3 | Viewed by 1224

Abstract

The effect of defects and microstructure on the mechanical properties of Ti-6Al-4V welds produced by tungsten inert gas welding; plasma arc welding; electron beam welding; and laser beam welding was studied in the present work. The mechanical properties of different weld types were [...] Read more.

The effect of defects and microstructure on the mechanical properties of Ti-6Al-4V welds produced by tungsten inert gas welding; plasma arc welding; electron beam welding; and laser beam welding was studied in the present work. The mechanical properties of different weld types were evaluated with respect to micro hardness; yield strength; ultimate tensile strength; ductility; and fatigue at room temperature and at elevated temperatures (200 °C and 250 °C). Metallographic investigation was carried out to characterize the microstructures of different weld types, and fractographic investigation was conducted to relate the effect of defects on fatigue performance. Electron and laser beam welding produced welds with finer microstructure, higher tensile ductility, and better fatigue performance than tungsten inert gas welding and plasma arc welding. Large pores, and pores located close to the specimen surface, were found to be most detrimental to fatigue life. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys)

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24 pages, 6651 KiB

Open AccessEditor’s ChoiceArticle

Application of Activated Carbons Obtained from Polymer Waste for the Adsorption of Dyes from Aqueous Solutions

by Katarzyna Jedynak and Barbara Charmas

Materials 2024, 17(3), 748; https://doi.org/10.3390/ma17030748 - 4 Feb 2024

Cited by 3 | Viewed by 1390

Abstract

Plastic waste disposal is a major environmental problem worldwide. One recycling method for polymeric materials is their conversion into carbon materials. Therefore, a process of obtaining activated carbons through the carbonization of waste CDs (as the selected carbon precursor) in an oxygen-free atmosphere, [...] Read more.

Plastic waste disposal is a major environmental problem worldwide. One recycling method for polymeric materials is their conversion into carbon materials. Therefore, a process of obtaining activated carbons through the carbonization of waste CDs (as the selected carbon precursor) in an oxygen-free atmosphere, and then the physical activation of the obtained material with CO₂, was developed. Dyes such as methylene blue (MB) and malachite green (MG) are commonly applied in industry, which contaminate the water environment to a large extent and have a harmful effect on living organisms; therefore, adsorption studies were carried out for these cationic dyes. The effects of the activation time on the physicochemical properties of the activated materials and the adsorption capacity of the dyes were investigated. The obtained microporous adsorbents were characterized by studying the porous structure based on low-temperature nitrogen adsorption/desorption, scanning electron microscopy (SEM-EDS), elemental analysis (CHNS), Raman spectroscopy, X-ray powder diffraction (XRD), infrared spectroscopy (ATR FT-IR), thermal analysis (TG, DTG, DTA), Boehm’s titration method, and pH_pzc (the point of zero charge) determination. Moreover, adsorption studies (equilibrium and kinetics) were carried out. The maximum adsorption capacities (q_{m exp}) of MB and MG (349 mg g⁻¹ and 274 mg g⁻¹, respectively) were identified for the obtained material after 8 h of activation. The results show that the use of waste CDs as a carbon precursor facilitates the production of low-cost and effective adsorbents. Full article

(This article belongs to the Special Issue Applications of Polymer Materials: Adsorption, Catalysis, and Degradation)

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16 pages, 10559 KiB

Open AccessEditor’s ChoiceArticle

Mechanical Characterization of Multifunctional Metal-Coated Polymer Lattice Structures

by Lizhe Wang, Liu He, Fuyuan Liu, Hang Yuan, Ji Li and Min Chen

Materials 2024, 17(3), 741; https://doi.org/10.3390/ma17030741 - 3 Feb 2024

Cited by 2 | Viewed by 1811

Abstract

Metal-coated lattice structures hold significant promise for customizing mechanical properties in diverse industrial applications, including the mechanical arms of unmanned aerial vehicles. However, their intricate geometries pose computational challenges, resulting in time-intensive and costly numerical evaluations. This study introduces a parameterization-based multiscale method [...] Read more.

Metal-coated lattice structures hold significant promise for customizing mechanical properties in diverse industrial applications, including the mechanical arms of unmanned aerial vehicles. However, their intricate geometries pose computational challenges, resulting in time-intensive and costly numerical evaluations. This study introduces a parameterization-based multiscale method to analyze body-centered cubic lattice structures with metal coatings. We establish the validity and precision of our proposed method with a comparative analysis of numerical results at the Representative Volume Element (RVE) scale and experimental findings, specifically addressing both elastic tensile and bending stiffness. Furthermore, we showcase the method’s accuracy in interpreting the bending stiffness of coated lattice structures using a homogenized material-based solid model, underscoring its effectiveness in predicting the elastic properties of such structures. In exploring the mechanical characterization of coated lattice structures, we unveil positive correlations between elastic tensile stiffness and both coating thickness and strut diameter. Additionally, the metal coating significantly enhances the structural elastic bending stiffness multiple times over. The diverse failure patterns observed in coated lattices under tensile and bending loads primarily stem from varied loading-induced stress states rather than external factors. This work not only mitigates computational challenges but also successfully bridges the gap between mesoscale RVE mechanical properties and those at the global structural scale. Full article

(This article belongs to the Section Porous Materials)

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15 pages, 5277 KiB

Open AccessEditor’s ChoiceArticle

Improvement of PbSn Solder Reliability with Ge Microalloying-Induced Optimization of Intermetallic Compounds Growth

by Zhibo Qu, Yilong Hao, Changhao Chen, Yong Wang, Shimeng Xu, Shuyuan Shi, Pengrong Lin and Xiaochen Xie

Materials 2024, 17(3), 724; https://doi.org/10.3390/ma17030724 - 2 Feb 2024

Viewed by 1101

Abstract

PbSn solders are used in semiconductor devices for aerospace or military purposes with high levels of reliability requirements. Microalloying has been widely adopted to improve the reliability for Pb-free solders, but its application in PbSn solders is scarce. In this article, the optimization [...] Read more.

PbSn solders are used in semiconductor devices for aerospace or military purposes with high levels of reliability requirements. Microalloying has been widely adopted to improve the reliability for Pb-free solders, but its application in PbSn solders is scarce. In this article, the optimization of PbSn solder reliability with Ge microalloying was investigated using both experimental and calculation methods. Intermetallic compounds (IMC) growth and morphologies evolution during reliability tests were considered to be the main factors of device failure. Through first-principle calculation, the growth mechanism of interfacial Ni₃Sn₄ was discussed, including the formation of vacancies, the Ni-vacancies exchange diffusion and the dominant Ni diffusion along the [1 0 0] direction. The doping of Ge in the cell increased the exchange energy barrier and thus inhibited the IMC development and coarsening trend. In three reliability tests, only 0.013 wt% Ge microalloying in Pb60Sn40 was able to reduce IMC thickness by an increment of 22.6~38.7%. The proposed Ge microalloying method in traditional PbSn solder could yield a prospective candidate for highly reliable applications. Full article

(This article belongs to the Special Issue Advanced Electronic Packaging Technology: From Hard to Soft)

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19 pages, 6857 KiB

Open AccessEditor’s ChoiceArticle

High-Entropy Diborides—Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative Study

by Ekaterina Pakhomova, Giacomo Cao, Roberto Orrù, Sebastiano Garroni, Paolo Ferro and Roberta Licheri

Materials 2024, 17(3), 718; https://doi.org/10.3390/ma17030718 - 2 Feb 2024

Cited by 3 | Viewed by 1309

Abstract

The reactive spark plasma sintering (R-SPS) method was compared in this work with the two-step SHS–SPS route, based on the combination of the self-propagating high-temperature synthesis (SHS) with the SPS process, for the fabrication of dense (Hf_0.2Mo_0.2Ti_0.2Ta [...] Read more.

The reactive spark plasma sintering (R-SPS) method was compared in this work with the two-step SHS–SPS route, based on the combination of the self-propagating high-temperature synthesis (SHS) with the SPS process, for the fabrication of dense (Hf_0.2Mo_0.2Ti_0.2Ta_0.2Nb_0.2)B₂–SiC and (Hf_0.2Mo_0.2Ti_0.2Ta_0.2Zr_0.2)B₂–SiC ceramics. A multiphase and inhomogeneous product, containing various borides, was obtained at 2000 °C/20 min by R-SPS from transition metals, B₄C, and Si. In contrast, if the same precursors were first reacted by SHS and then processed by SPS under the optimized condition of 1800 °C/20 min, the desired ceramics were successfully attained. The resulting sintered samples possessed relative densities above 97% and displayed uniform microstructures with residual oxide content <2.4 wt.%. The presence of SiC made the sintering temperature milder, i.e., 150 °C below that needed by the corresponding additive-free system. The fracture toughness was also markedly improved, particularly when considering the Nb-containing system processed at 1800 °C/20 min, whereas the fracture toughness progressively decreased (from 7.35 to 5.36 MPa m^1/2) as the SPS conditions became more severe. SiC addition was found to inhibit the volatilization of metal oxides like MoO₃ formed during oxidation experiments, thus avoiding mass loss in the ceramics. The benefits above also likely took advantage of the fact that the two composite constituents were synthesized in parallel, according to the SHS–SPS approach, rather than being produced separately and combined subsequently, so that strong interfaces between them were formed. Full article

(This article belongs to the Special Issue High-Entropy Ceramics: Synthesis and Applications)

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