Materials

13 pages, 2956 KiB

Open AccessEditor’s ChoiceArticle

Thioether-Linked Liquid Crystal Trimers: Odd–Even Effects of Spacers and the Influence of Thioether Bonds on Phase Behavior

by Yuki Arakawa, Kenta Komatsu, Yuko Ishida, Takuma Shiba and Hideto Tsuji

Materials 2022, 15(5), 1709; https://doi.org/10.3390/ma15051709 - 24 Feb 2022

Cited by 15 | Viewed by 2910

Abstract

We report the synthesis, phase-transition behavior, and mesophase structures of the first homologous series of thioether-linked liquid crystal (LC) trimers, 4,4′-bis[ω-(4-cyanobiphenyl-4′-ylthio)alkoxy]biphenyls (CBSnOBOnSCB with a wide range of spacer carbon numbers, n = 3–11). All CBSnOBOnSCB [...] Read more.

We report the synthesis, phase-transition behavior, and mesophase structures of the first homologous series of thioether-linked liquid crystal (LC) trimers, 4,4′-bis[ω-(4-cyanobiphenyl-4′-ylthio)alkoxy]biphenyls (CBSnOBOnSCB with a wide range of spacer carbon numbers, n = 3–11). All CBSnOBOnSCB homologs exhibited LC phases. Interestingly, even-n and odd-n homologs showed monotropic layered smectic A (SmA) and pseudo-layered twist-bend nematic (N_TB) phases, respectively, below a nematic (N) phase. This alternate formation, which depends on spacer chain parity, is attributed to different average molecular shapes, which are associated with the relative orientations of the biphenyl moieties: linear and bent shapes for even-n and odd-n homologs, respectively. In addition, X-ray diffraction analysis indicated a strong cybotactic N phase tendency, with a triply intercalated structure. The phase-transition behavior and LC phase structures of thioether-linked CBSnOBOnSCB were compared with those of the all-ether-linked classic LC trimers CBOnOBOnOCB. Overall, thioether linkages endowed CBSnOBOnSCB with a monotropic LC tendency and lowered phase-transition temperatures, compared to those of CBOnOBOnOCB, for the same n. This is attributed to enhanced flexibility and bending (less molecular anisotropy) of the molecules, caused by the greater bond flexibility and smaller inner bond angles of the C–S–C bonds, compared to those of the C–O–C bonds. Full article

(This article belongs to the Special Issue Advances in Liquid Crystals)

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12 pages, 3152 KiB

Open AccessEditor’s ChoiceArticle

Sunlike White Light-Emitting Diodes Based on Rare-Earth-Free Luminescent Materials

by Amador Menéndez-Velázquez, Dolores Morales and Ana Belén García-Delgado

Materials 2022, 15(5), 1680; https://doi.org/10.3390/ma15051680 - 23 Feb 2022

Cited by 19 | Viewed by 2864

Abstract

Solid-state lighting (SSL) sources based on light-emitting diodes represent the new generation of highly efficient illumination systems that significantly impact energy-saving. The development of white light-emitting diodes (WLEDs) with a combination of high color rendering index (CRI) and high deep-red color rendering R [...] Read more.

Solid-state lighting (SSL) sources based on light-emitting diodes represent the new generation of highly efficient illumination systems that significantly impact energy-saving. The development of white light-emitting diodes (WLEDs) with a combination of high color rendering index (CRI) and high deep-red color rendering R₉ is an important challenge in the field of solid-state lighting. On the other hand, most WLEDs use rare-earth inorganic luminescent materials. The annual demand for rare-earth metals has doubled to 125,000 tons in 15 years, and the demand is projected to reach 315,000 tons in 2030. The explosion in demand for these materials, combined with a monopolistic supply source, represents a real risk for the development of WLEDs in the next few years. Luminescent organic materials are a relevant and promising alternative. Here, we report a WLED with a very high CRI of 95.7 and R₉ of 78.7, obtained using a combination of a blue LED chip (excitation source) and two organic luminescent dyes (Coumarin 6 and Lumogen Red) acting as spectral converters in a multilayer remote phosphor configuration. To the best of our knowledge, this is the first rare-earth-free WLED with such high values of CRI and R₉. Full article

(This article belongs to the Special Issue Advanced Materials for Optical Applications and Devices)

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23 pages, 6668 KiB

Open AccessEditor’s ChoiceReview

MXene (Ti₃C₂T_x)-Embedded Nanocomposite Hydrogels for Biomedical Applications: A Review

by Fouad Damiri, Md. Habibur Rahman, Mehrukh Zehravi, Aeshah A. Awaji, Mohammed Z. Nasrullah, Heba A. Gad, Mutasem Z. Bani-Fwaz, Rajender S. Varma, Mousa O. Germoush, Hamdan S. Al-malky, Amany A. Sayed, Satish Rojekar, Mohamed M. Abdel-Daim and Mohammed Berrada

Materials 2022, 15(5), 1666; https://doi.org/10.3390/ma15051666 - 23 Feb 2022

Cited by 61 | Viewed by 7679

Abstract

Polymeric nanocomposites have been outstanding functional materials and have garnered immense attention as sustainable materials to address multi-disciplinary problems. MXenes have emerged as a newer class of 2D materials that produce metallic conductivity upon interaction with hydrophilic species, and their delamination affords monolayer [...] Read more.

Polymeric nanocomposites have been outstanding functional materials and have garnered immense attention as sustainable materials to address multi-disciplinary problems. MXenes have emerged as a newer class of 2D materials that produce metallic conductivity upon interaction with hydrophilic species, and their delamination affords monolayer nanoplatelets of a thickness of about one nm and a side size in the micrometer range. Delaminated MXene has a high aspect ratio, making it an alluring nanofiller for multifunctional polymer nanocomposites. Herein, we have classified and discussed the structure, properties and application of major polysaccharide-based electroactive hydrogels (hyaluronic acid (HA), alginate sodium (SA), chitosan (CS) and cellulose) in biomedical applications, starting with the brief historical account of MXene’s development followed by successive discussions on the synthesis methods, structures and properties of nanocomposites encompassing polysaccharides and MXenes, including their biomedical applications, cytotoxicity and biocompatibility aspects. Finally, the MXenes and their utility in the biomedical arena is deliberated with an eye on potential opportunities and challenges anticipated for them in the future, thus promoting their multifaceted applications. Full article

(This article belongs to the Special Issue MXenes and Their Composites for Emerging Applications)

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17 pages, 10153 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Corrosion Performance of Extruded and Forged WE43 Mg Alloy

by Guonan Liu, Jilei Xu, Baojing Feng, Jinhui Liu, Dongqing Qi, Wenzhan Huang, Peixu Yang and Shaojun Zhang

Materials 2022, 15(5), 1622; https://doi.org/10.3390/ma15051622 - 22 Feb 2022

Cited by 11 | Viewed by 2729

Abstract

Adjusting the microstructure through the deformation process is one of the ways to improve the properties of Mg alloys. Most studies have focused on the influence of the microstructure after deformation treatment on the mechanical properties of Mg alloys. In this paper, extruded [...] Read more.

Adjusting the microstructure through the deformation process is one of the ways to improve the properties of Mg alloys. Most studies have focused on the influence of the microstructure after deformation treatment on the mechanical properties of Mg alloys. In this paper, extruded and forged Mg-Gd-Y-Nd-Zr alloys were selected to investigate the corrosion performance of two deformed magnesium alloys immersed in 0.6 M NaCl solution using a hydrogen evolution test, a weight loss test, an immersion experiment, and an electrochemical test. The results showed that WE43 alloys undergoing different deformation treatments presented different microstructures, which led to different corrosion behaviors and corrosion resistance. The extruded WE43 alloy showed uniform corrosion, while the forged WE43 alloy suffered severe local galvanic corrosion. Meanwhile, the corrosion rate of the forged WE43 alloy was about four times faster than that of the extruded WE43 alloy. Full article

(This article belongs to the Special Issue Corrosion and Corrosion Inhibition of Metals and Their Alloys)

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15 pages, 4882 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Progress and Challenges of InGaN/GaN-Based Core–Shell Microrod LEDs

by Johanna Meier and Gerd Bacher

Materials 2022, 15(5), 1626; https://doi.org/10.3390/ma15051626 - 22 Feb 2022

Cited by 15 | Viewed by 3837

Abstract

LEDs based on planar InGaN/GaN heterostructures define an important standard for solid-state lighting. However, one drawback is the polarization field of the wurtzite heterostructure impacting both electron–hole overlap and emission energy. Three-dimensional core–shell microrods offer field-free sidewalls, thus improving radiative recombination rates while [...] Read more.

LEDs based on planar InGaN/GaN heterostructures define an important standard for solid-state lighting. However, one drawback is the polarization field of the wurtzite heterostructure impacting both electron–hole overlap and emission energy. Three-dimensional core–shell microrods offer field-free sidewalls, thus improving radiative recombination rates while simultaneously increasing the light-emitting area per substrate size. Despite those promises, microrods have still not replaced planar devices. In this review, we discuss the progress in device processing and analysis of microrod LEDs and emphasize the perspectives related to the 3D device architecture from an applications point of view. Full article

(This article belongs to the Special Issue Optoelectronic Devices: 2021)

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20 pages, 7142 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Microstructure on the Flexural Properties of 3D Printed Zirconia Part via Digital Light Processing Technology

by Boran Wang, Ali Arab, Jing Xie and Pengwan Chen

Materials 2022, 15(4), 1602; https://doi.org/10.3390/ma15041602 - 21 Feb 2022

Cited by 20 | Viewed by 3628

Abstract

In recent years, additive manufacturing of ceramics is becoming of increasing interest due to the possibility of the fabrication of complex shaped parts. However, the fabrication of a fully dense bulk ceramic part without cracks and defects is still challenging. In the presented [...] Read more.

In recent years, additive manufacturing of ceramics is becoming of increasing interest due to the possibility of the fabrication of complex shaped parts. However, the fabrication of a fully dense bulk ceramic part without cracks and defects is still challenging. In the presented work, the digital light processing method was introduced for fabricating zirconia parts. The flexural properties of the printed zirconia were systematically investigated via a three-point bending test with the digital image correlation method, scanning electron microscopy observation and fractography analysis. Due to the anisotropy of the sample, the bending deformation behaviors of the zirconia samples in the parallel and vertical printing directions were significantly different. The flexural strength and the related elastic modulus of the samples under vertical loading were higher than that of the parallel loading, as the in-plane strength is higher than that of the interlayer strength. The maximum horizontal strain always appeared at the bottom center before the failure for the parallel loading case; while the maximum horizontal strain for the vertical loading moved upward from the bottom center to the top center. There was a clear dividing line between the minimum perpendicular strain and the maximum perpendicular strain of the samples under parallel loading; however, under vertical loading, the perpendicular strain declined from the bottom to the top along the crack path. The surrounding dense part of the sintered sample (a few hundred microns) was mainly composed of large and straight cracks between printing layers, whereas the interior contained numerous small winding cracks. The intense cracks inside the sample led to a low flexural property compared to other well-prepared zirconia samples, which the inadequate additive formulations would be the main reason for the generation of cracks. A better understanding of the additive formulation (particularly the dispersant) and the debinding-sintering process are necessary for future improvement. Full article

(This article belongs to the Section Advanced and Functional Ceramics and Glasses)

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39 pages, 72409 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Photothermal and Photodynamic Therapy of Tumors with Plasmonic Nanoparticles: Challenges and Prospects

by Alla B. Bucharskaya, Nikolai G. Khlebtsov, Boris N. Khlebtsov, Galina N. Maslyakova, Nikita A. Navolokin, Vadim D. Genin, Elina A. Genina and Valery V. Tuchin

Materials 2022, 15(4), 1606; https://doi.org/10.3390/ma15041606 - 21 Feb 2022

Cited by 51 | Viewed by 6790

Abstract

Cancer remains one of the leading causes of death in the world. For a number of neoplasms, the efficiency of conventional chemo- and radiation therapies is insufficient because of drug resistance and marked toxicity. Plasmonic photothermal therapy (PPT) using local hyperthermia induced by [...] Read more.

Cancer remains one of the leading causes of death in the world. For a number of neoplasms, the efficiency of conventional chemo- and radiation therapies is insufficient because of drug resistance and marked toxicity. Plasmonic photothermal therapy (PPT) using local hyperthermia induced by gold nanoparticles (AuNPs) has recently been extensively explored in tumor treatment. However, despite attractive promises, the current PPT status is limited by laboratory experiments, academic papers, and only a few preclinical studies. Unfortunately, most nanoformulations still share a similar fate: great laboratory promises and fair preclinical trials. This review discusses the current challenges and prospects of plasmonic nanomedicine based on PPT and photodynamic therapy (PDT). We start with consideration of the fundamental principles underlying plasmonic properties of AuNPs to tune their plasmon resonance for the desired NIR-I, NIR-2, and SWIR optical windows. The basic principles for simulation of optical cross-sections and plasmonic heating under CW and pulsed irradiation are discussed. Then, we consider the state-of-the-art methods for wet chemical synthesis of the most popular PPPT AuNPs such as silica/gold nanoshells, Au nanostars, nanorods, and nanocages. The photothermal efficiencies of these nanoparticles are compared, and their applications to current nanomedicine are shortly discussed. In a separate section, we discuss the fabrication of gold and other nanoparticles by the pulsed laser ablation in liquid method. The second part of the review is devoted to our recent experimental results on laser-activated interaction of AuNPs with tumor and healthy tissues and current achievements of other research groups in this application area. The unresolved issues of PPT are the significant accumulation of AuNPs in the organs of the mononuclear phagocyte system, causing potential toxic effects of nanoparticles, and the possibility of tumor recurrence due to the presence of survived tumor cells. The prospective ways of solving these problems are discussed, including developing combined antitumor therapy based on combined PPT and PDT. In the conclusion section, we summarize the most urgent needs of current PPT-based nanomedicine. Full article

(This article belongs to the Special Issue Feature Paper in Optical and Photonic Materials)

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19 pages, 6261 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Advanced Carbon Reinforced Concrete Technologies for Façade Elements of Nearly Zero-Energy Buildings

by Robert Kraft, Alexander Kahnt, Otto Grauer, Mike Thieme, Daniel Sebastian Wolz, Dominik Schlüter, Matthias Tietze, Manfred Curbach, Klaus Holschemacher, Hubert Jäger and Robert Böhm

Materials 2022, 15(4), 1619; https://doi.org/10.3390/ma15041619 - 21 Feb 2022

Cited by 12 | Viewed by 4629

Abstract

The building sector accounts for approx. 40% of total energy consumption and approx. 36% of all greenhouse gas emissions in Europe. As the EU climate targets for 2030 call for a reduction of greenhouse gas emissions by more than half compared to the [...] Read more.

The building sector accounts for approx. 40% of total energy consumption and approx. 36% of all greenhouse gas emissions in Europe. As the EU climate targets for 2030 call for a reduction of greenhouse gas emissions by more than half compared to the emissions of 1990 and also aim for climate neutrality by 2050, there is an urgent need to achieve a significant decrease in the energy use in buildings towards Nearly Zero-Energy Buildings (nZEBs). As the energy footprint of buildings includes the energy and greenhouse gas consumption both in the construction phase and during service life, nZEB solutions have to provide energy-efficient and less carbon-intensive building materials, specific thermal insulation solutions, and a corresponding design of the nZEB. Carbon reinforced concrete (CRC) materials have proven to be excellent candidate materials for concrete-based nZEBs since they are characterized by a significantly lower CO₂ consumption during component production and much a longer lifecycle. The corresponding CRC technology has been successively implemented in the last two decades and first pure CRC-based buildings are currently being built. This article presents a novel material system that combines CRC technology and suitable multifunctional insulation materials as a sandwich system in order to meet future nZEB requirements. Because of its importance for the life cycle stage of production, cost-efficient carbon fibers (CF) from renewable resources like lignin are used as reinforcing material, and reinforcement systems based on such CF are developed. Cutting edge approaches to produce ultra-thin lightweight CF reinforced concrete panels are discussed with regard to their nZEB relevance. For the life cycle stage of the utilization phase, the thermal insulation properties of core materials are optimized. In this context, novel sandwich composites with thin CRC layers and a cellular lightweight concrete core are proposed as a promising solution for façade elements as the sandwich core can additionally be combined with an aerogel-based insulation. The concepts to realize such sandwich façade elements will be described here along with a fully automated manufacturing process to produce such structures. The findings of this study provide clear evidence on the promising capabilities of the CRC technology for nZEBs on the one hand and on the necessity for further research on optimizing the energy footprint of CRC-based structural elements on the other hand. Full article

(This article belongs to the Special Issue Composite Materials for Nearly Zero Emission Applications)

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16 pages, 3357 KiB

Open AccessEditor’s ChoiceArticle

Synthesis and Structural Characterization of CaO-P₂O₅-CaF:CuO Glasses with Antitumoral Effect on Skin Cancer Cells

by Nicoleta Simona Vedeanu, Cristian Lujerdean, Marius Zăhan, Daniel Severus Dezmirean, Lucian Barbu-Tudoran, Grigore Damian and Răzvan Ștefan

Materials 2022, 15(4), 1526; https://doi.org/10.3390/ma15041526 - 18 Feb 2022

Cited by 2 | Viewed by 2166

Abstract

Copper is one of the most used therapeutic metallic elements in biomedicine, ranging from antibacterial approaches to developing new complexes in cancer therapy. In the present investigation, we developed a novel xCuO∙(100 − x) [CaF₂∙3P₂O₅∙CaO] glass system [...] Read more.

Copper is one of the most used therapeutic metallic elements in biomedicine, ranging from antibacterial approaches to developing new complexes in cancer therapy. In the present investigation, we developed a novel xCuO∙(100 − x) [CaF₂∙3P₂O₅∙CaO] glass system with 0 ≤ x ≤ 16 mol% in order to determine the influence of doping on the composition structure of glasses. The samples were characterized by dissolution tests, pH measurements, Fourier-transform infrared spectroscopy (FT-IR), electron paramagnetic resonance (EPR), Scanning Electron Microscopy with energy dispersive spectroscopy (SEM-EDX) and afterward, their antitumor character was assessed. The glasses were mostly soluble in the aqueous medium, their dissolution rate being directly proportional to the increase in pH and the level of doping up to x = 8 mol%. FT-IR spectra of glass samples show the presence of all structural units characteristic to P₂O₅ in different rates and directly depending on the depolymerization process. SEM-EDX results revealed the presence of an amorphous glass structure composed of P, O, Ca, and Cu elements. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay showed strong cytotoxicity for tumoral cells A375 even in low concentrations for Cu-treatment. In contrast, the copper-free matrix (without Cu) determined a proliferative effect of over 70% viability for all concentrations used. Full article

(This article belongs to the Special Issue Optical and Magnetic Properties of Glass and Glass Ceramics)

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37 pages, 548 KiB

Open AccessEditor’s ChoiceArticle

Analytical Methods for Causality Evaluation of Photonic Materials

by Tomasz P. Stefański, Jacek Gulgowski and Kosmas L. Tsakmakidis

Materials 2022, 15(4), 1536; https://doi.org/10.3390/ma15041536 - 18 Feb 2022

Cited by 4 | Viewed by 1710

Abstract

We comprehensively review several general methods and analytical tools used for causality evaluation of photonic materials. Our objective is to call to mind and then formulate, on a mathematically rigorous basis, a set of theorems which can answer the question whether a considered [...] Read more.

We comprehensively review several general methods and analytical tools used for causality evaluation of photonic materials. Our objective is to call to mind and then formulate, on a mathematically rigorous basis, a set of theorems which can answer the question whether a considered material model is causal or not. For this purpose, a set of various distributional theorems presented in literature is collected as the distributional version of the Titchmarsh theorem, allowing for evaluation of causality in complicated electromagnetic systems. Furthermore, we correct the existing material models with the use of distribution theory in order to obtain their causal formulations. In addition to the well-known Kramers–Krönig (K–K) relations, we overview four further methods which can be used to assess causality of given dispersion relations, when calculations of integrals involved in the K–K relations are challenging or even impossible. Depending on the given problem, optimal approaches allowing us to prove either the causality or lack thereof are pointed out. These methodologies should be useful for scientists and engineers analyzing causality problems in electrodynamics and optics, particularly with regard to photonic materials, when the involved mathematical distributions have to be invoked. Full article

(This article belongs to the Special Issue Photonic Materials for Optical Waveguide Application)

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26 pages, 14735 KiB

Open AccessEditor’s ChoiceReview

Carbon Nanotube Devices for Quantum Technology

by Andrey Baydin, Fuyang Tay, Jichao Fan, Manukumara Manjappa, Weilu Gao and Junichiro Kono

Materials 2022, 15(4), 1535; https://doi.org/10.3390/ma15041535 - 18 Feb 2022

Cited by 45 | Viewed by 9693

Abstract

Carbon nanotubes, quintessentially one-dimensional quantum objects, possess a variety of electrical, optical, and mechanical properties that are suited for developing devices that operate on quantum mechanical principles. The states of one-dimensional electrons, excitons, and phonons in carbon nanotubes with exceptionally large quantization energies [...] Read more.

Carbon nanotubes, quintessentially one-dimensional quantum objects, possess a variety of electrical, optical, and mechanical properties that are suited for developing devices that operate on quantum mechanical principles. The states of one-dimensional electrons, excitons, and phonons in carbon nanotubes with exceptionally large quantization energies are promising for high-operating-temperature quantum devices. Here, we discuss recent progress in the development of carbon-nanotube-based devices for quantum technology, i.e., quantum mechanical strategies for revolutionizing computation, sensing, and communication. We cover fundamental properties of carbon nanotubes, their growth and purification methods, and methodologies for assembling them into architectures of ordered nanotubes that manifest macroscopic quantum properties. Most importantly, recent developments and proposals for quantum information processing devices based on individual and assembled nanotubes are reviewed. Full article

(This article belongs to the Special Issue Materials Opportunities and Challenges for Quantum Information Processors)

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17 pages, 5003 KiB

Open AccessEditor’s ChoiceArticle

Dissolution of Portlandite in Pure Water: Part 2 Atomistic Kinetic Monte Carlo (KMC) Approach

by Mohammadreza Izadifar, Neven Ukrainczyk, Khondakar Mohammad Salah Uddin, Bernhard Middendorf and Eduardus Koenders

Materials 2022, 15(4), 1442; https://doi.org/10.3390/ma15041442 - 15 Feb 2022

Cited by 29 | Viewed by 3581

Abstract

Portlandite, as a most soluble cement hydration reaction product, affects mechanical and durability properties of cementitious materials. In the present work, an atomistic kinetic Monte Carlo (KMC) upscaling approach is implemented in MATLAB code in order to investigate the dissolution time and morphology [...] Read more.

Portlandite, as a most soluble cement hydration reaction product, affects mechanical and durability properties of cementitious materials. In the present work, an atomistic kinetic Monte Carlo (KMC) upscaling approach is implemented in MATLAB code in order to investigate the dissolution time and morphology changes of a hexagonal platelet portlandite crystal. First, the atomistic rate constants of individual Ca dissolution events are computed by a transition state theory equation based on inputs of the computed activation energies (ΔG*) obtained through the metadynamics computational method (Part 1 of paper). Four different facets (100 or

\bar{1} 00

, 010 or 0

\bar{1}

0,

\bar{1} 10

or

1 \bar{1} 0

, and 001 or 00

\bar{1}

) are considered, resulting in a total of 16 different atomistic event scenarios. Results of the upscaled KMC simulations demonstrate that dissolution process initially takes place from edges, sides, and facets of 010 or 0

\bar{1}

0 of the crystal morphology. The steady-state dissolution rate for the most reactive facets (010 or 0

\bar{1} 0

) was computed to be 1.0443 mol/(s cm²); however, 0.0032 mol/(s cm²) for

\bar{1} 10

or

1 \bar{1} 0

, 2.672 × 10⁻⁷ mol/(s cm²) for 001 or 00

\bar{1}

, and 0.31 × 10⁻¹⁶ mol/(s cm²) for 100 or

\bar{1} 00

were represented in a decreasing order for less reactive facets. Obtained upscaled dissolution rates between each facet resulted in a huge (16 orders of magnitude) difference, reflecting the importance of crystallographic orientation of the exposed facets. Full article

(This article belongs to the Special Issue Mathematical Modeling of Building Materials)

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11 pages, 6224 KiB

Open AccessEditor’s ChoiceArticle

Evaluating the X-ray-Shielding Performance of Graphene-Oxide-Coated Nanocomposite Fabric

by Serhat Süha Türkaslan, Şule Sultan Ugur, Banu Esencan Türkaslan and Nicholas Fantuzzi

Materials 2022, 15(4), 1441; https://doi.org/10.3390/ma15041441 - 15 Feb 2022

Cited by 25 | Viewed by 4107

Abstract

Exposure to ionizing radiation (IR) during diagnostic medical procedures brings certain risks, especially when experiencing recurrent exposures. The fabrication of nano-based composites, doped with different nanoparticles, have been suggested as effective shielding materials to replace conventional lead-based ones in material sciences and nanotechnology. [...] Read more.

Exposure to ionizing radiation (IR) during diagnostic medical procedures brings certain risks, especially when experiencing recurrent exposures. The fabrication of nano-based composites, doped with different nanoparticles, have been suggested as effective shielding materials to replace conventional lead-based ones in material sciences and nanotechnology. In this study, commercially available fabrics, used to produce scrubs and gowns for clinical staff, are modified utilizing graphene oxide (GO) nanoparticles using a layer-by-layer (LBL) technique. GO was obtained from graphite through environmentally friendly technology by using a modified–improved Hummers’ method without NaNO₃. Lightweight, flexible, air- and water-permeable shielding materials are produced that are wearable in all-day clinical practice. The nanoparticles are kept to a minimum at 1 wt%; however, utilizing the LBL technique they are distributed evenly along the fibers of the fabrics to achieve as much shielding effect as possible. The evaluation of samples is accomplished by simulating real-time routine clinical procedures and the radiographic programs and devices used daily. The GO-coated nanocomposite fabrics demonstrated promising results for X-ray shielding. Full article

(This article belongs to the Special Issue Radiation Shielding Materials)

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8 pages, 9530 KiB

Open AccessEditor’s ChoiceArticle

Microstructure and Mechanical Properties of Co₃₂Cr₂₈Ni₃₂.₉₄Al₄.₀₆Ti₃ High-Entropy Alloy

by Jinquan Guo, Chaozhongzheng Tang and Huan Sheng Lai

Materials 2022, 15(4), 1444; https://doi.org/10.3390/ma15041444 - 15 Feb 2022

Cited by 10 | Viewed by 2411

Abstract

High-entropy alloys have good application prospects in nuclear power plants due to their excellent mechanical properties and radiation resistance. In this paper, the microstructure of the Co₃₂Cr₂₈Ni₃₂.₉₄Al₄.₀₆Ti₃ high-entropy alloy was [...] Read more.

High-entropy alloys have good application prospects in nuclear power plants due to their excellent mechanical properties and radiation resistance. In this paper, the microstructure of the Co₃₂Cr₂₈Ni₃₂.₉₄Al₄.₀₆Ti₃ high-entropy alloy was researched using metallurgical microscopy, X-ray diffraction, and scanning electron microscopy. The mechanical properties were tested using a Vickers microhardness tester and a tensile testing machine, respectively. The results showed that Co₃₂Cr₂₈Ni₃₂.₉₄Al₄.₀₆Ti₃ had a single-phase, disordered, face-centered, cubic solid-solution structure and was strengthened by solid solution. The alloy lattice parameter and density were estimated as 0.304 nm and 7.89 g/cm³, respectively. The test results indicated that the alloy had satisfactory mechanical properties with yield stress and tensile strength of about 530 MPa and 985 MPa, respectively. Full article

(This article belongs to the Special Issue Advances in Smart Materials and Structures)

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10 pages, 1777 KiB

Open AccessEditor’s ChoiceArticle

Superplastic Deformation of Alumina Composites Reinforced with Carbon Nanofibers and with Graphene Oxide Sintered by SPS—Experimental Testing and Theoretical Interpretation

by Rafael Cano-Crespo, César Retamal, Miguel Lagos and Francisco Luis Cumbrera

Materials 2022, 15(4), 1396; https://doi.org/10.3390/ma15041396 - 14 Feb 2022

Viewed by 1679

Abstract

The superplastic behavior of alumina-based nanostructured ceramics (Al₂O₃) is an important issue in the world of materials. The main body of this paper is an analysis of the creep behavior of polycrystals, with grain boundary sliding as the main [...] Read more.

The superplastic behavior of alumina-based nanostructured ceramics (Al₂O₃) is an important issue in the world of materials. The main body of this paper is an analysis of the creep behavior of polycrystals, with grain boundary sliding as the main deformation mechanism at high temperatures. Concomitant accommodation of grain shapes to preserve spatial continuity has a comparatively small effect on the strain rate. The constitutive equations for small deformations, relating strain and strain rate, derived from two models for grain sliding, are compared with the experimental data with their respective uncertainties. The data follow from experiments on the plastic deformation of alumina composites reinforced, on the one hand by graphene oxide, and on the other hand by carbon nanofibers sintered by SPS. The results show good agreement between experiment and theory for these advanced ceramics, particularly for one of the assumed models. The values obtained of ξ² for model A were in the interval 0.0002–0.1189, and for model B were in the interval 0.000001–0.0561. The values obtained of R² for model A were in the interval 0.9122–0.9994, and for model B were in the interval 0.9586–0.9999. The threshold stress was between (3.05 · 10⁻¹⁵–25.68) MPa. Full article

(This article belongs to the Special Issue Mechanical Properties and Electrical Conductivity of Ceramics)

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23 pages, 185666 KiB

Open AccessEditor’s ChoiceArticle

Passive Photonic Integrated Circuits Elements Fabricated on a Silicon Nitride Platform

by Marcin Lelit, Mateusz Słowikowski, Maciej Filipiak, Marcin Juchniewicz, Bartłomiej Stonio, Bartosz Michalak, Krystian Pavłov, Marcin Myśliwiec, Piotr Wiśniewski, Andrzej Kaźmierczak, Krzysztof Anders, Stanisław Stopiński, Romuald B. Beck and Ryszard Piramidowicz

Materials 2022, 15(4), 1398; https://doi.org/10.3390/ma15041398 - 14 Feb 2022

Cited by 17 | Viewed by 6092

Abstract

The fabrication processes for silicon nitride photonic integrated circuits evolved from microelectronics components technology—basic processes have common roots and can be executed using the same type of equipment. In comparison to that of electronics components, passive photonic structures require fewer manufacturing steps and [...] Read more.

The fabrication processes for silicon nitride photonic integrated circuits evolved from microelectronics components technology—basic processes have common roots and can be executed using the same type of equipment. In comparison to that of electronics components, passive photonic structures require fewer manufacturing steps and fabricated elements have larger critical dimensions. In this work, we present and discuss our first results on design and development of fundamental building blocks for silicon nitride integrated photonic platform. The scope of the work covers the full design and manufacturing chain, from numerical simulations of optical elements, design, and fabrication of the test structures to optical characterization and analysis the results. In particular, technological processes were developed and evaluated for fabrication of the waveguides (WGs), multimode interferometers (MMIs), and arrayed waveguide gratings (AWGs), which confirmed the potential of the technology and correctness of the proposed approach. Full article

(This article belongs to the Special Issue Trends in Electronic and Optoelectronic Materials)

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13 pages, 4334 KiB

Open AccessEditor’s ChoiceArticle

Pressure-Induced Superconductivity in Iron-Based Spin-Ladder Compound BaFe_2+δ(S_1−xSe_x)₃

by Hiroki Takahashi, Ryosuke Kikuchi, Chizuru Kawashima, Satoshi Imaizumi, Takuya Aoyama and Kenya Ohgushi

Materials 2022, 15(4), 1401; https://doi.org/10.3390/ma15041401 - 14 Feb 2022

Cited by 2 | Viewed by 3139

Abstract

The iron-based superconductors had a significant impact on condensed matter physics. They have a common structural motif of a two-dimensional square iron lattice and exhibit fruitful physical properties as a strongly correlated electron system. During the extensive investigations, quasi-one-dimensional iron-based spin-ladder compounds attracted [...] Read more.

The iron-based superconductors had a significant impact on condensed matter physics. They have a common structural motif of a two-dimensional square iron lattice and exhibit fruitful physical properties as a strongly correlated electron system. During the extensive investigations, quasi-one-dimensional iron-based spin-ladder compounds attracted much attention as a platform for studying the interplay between magnetic and orbital ordering. In these compounds, BaFe₂S₃ and BaFe₂Se₃ were found to exhibit superconductivity under high pressure, having a different crystal and magnetic structure at low temperature. We report a brief review of the iron-based spin-ladder compound and recent studies for BaFe_2+δ(S_1−xSe_x)₃. BaFe₂(S_0.75 Se_0.25)₃ is in the vicinity of the boundary of two different magnetic phases and it is intriguing to perform high pressure experiments for studying superconductivity, since effects of large magnetic fluctuations on superconductivity are expected. The effect of iron stoichiometry on the interplay between magnetism and superconductivity is also studied by changing the iron concentration in BaFe_2+δSe₃. Full article

(This article belongs to the Special Issue Quantum Materials and Emergent Phenomena under Extreme Conditions)

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13 pages, 6985 KiB

Open AccessEditor’s ChoiceArticle

Dissolution of Portlandite in Pure Water: Part 1 Molecular Dynamics (MD) Approach

by Khondakar Mohammad Salah Uddin, Mohammadreza Izadifar, Neven Ukrainczyk, Eduardus Koenders and Bernhard Middendorf

Materials 2022, 15(4), 1404; https://doi.org/10.3390/ma15041404 - 14 Feb 2022

Cited by 18 | Viewed by 3782

Abstract

The current contribution proposes a multi-scale bridging modeling approach for the dissolution of crystals to connect the atomistic scale to the (sub-) micro-scale. This is demonstrated in the example of dissolution of portlandite, as a relatively simple benchmarking example for cementitious materials. Moreover, [...] Read more.

The current contribution proposes a multi-scale bridging modeling approach for the dissolution of crystals to connect the atomistic scale to the (sub-) micro-scale. This is demonstrated in the example of dissolution of portlandite, as a relatively simple benchmarking example for cementitious materials. Moreover, dissolution kinetics is also important for other industrial processes, e.g., acid gas absorption and pH control. In this work, the biased molecular dynamics (metadynamics) coupled with reactive force field is employed to calculate the reaction path as a free energy surface of calcium dissolution at 298 K in water from the different crystal facets of portlandite. It is also explained why the reactivity of the (010), (100), and (1

\bar{1}

0) crystal facet is higher compared to the (001) facet. In addition, the influence of neighboring Ca crystal sites arrangements on the atomistic dissolution rates is explained as necessary scenarios for the upscaling. The calculated rate constants of all atomistic reaction scenarios provided an input catalog ready to be used in an upscaling kinetic Monte Carlo (KMC) approach. Full article

(This article belongs to the Special Issue Mathematical Modeling of Building Materials)

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13 pages, 9087 KiB

Open AccessEditor’s ChoiceArticle

A CuNi-Loaded Porous Magnetic Soft Material: Preparation, Characterization and Magnetic Field-Controlled Modulus

by Jingyuan Bai, Xuejiao Wang, Meilin Zhang, Jin Zhang, Xiaolin Chen, Yanan An and Renguo Guan

Materials 2022, 15(4), 1412; https://doi.org/10.3390/ma15041412 - 14 Feb 2022

Cited by 1 | Viewed by 2162

Abstract

Novel porous magnetic soft materials (pMSMs) based on a poly (vinyl alcohol) (PVA) porous matrix filled with CuNi nanoparticles (NPs) of around 70 nm were synthesized. Initially, magnetic CuNi NPs were fabricated by the reduction of Ni and Cu ions with hydrazine hydrate [...] Read more.

Novel porous magnetic soft materials (pMSMs) based on a poly (vinyl alcohol) (PVA) porous matrix filled with CuNi nanoparticles (NPs) of around 70 nm were synthesized. Initially, magnetic CuNi NPs were fabricated by the reduction of Ni and Cu ions with hydrazine hydrate in ethylene glycol medium in the absence of other capping agents. The pMSMs are subsequently fabricated by mixing CuNi NPs and PVA through freezing-drying process. The as-obtained pMSMs can respond to a magnetic field, i.e., the compressive modulus increase under a magnetic field of 0.23 T. The experimental results indicate that CuNi NPs can easily move to form chain-like structures under the application of a magnetic field. A combination of direct observation and finite element modeling has shown that under the influence of a magnetic field, chain-like aggregates of CuNi NPs lead to self-reinforcement of the pMSMs and, thus, to the increased compressive modulus. From a technological point of view, these materials with good magnetic responsiveness and moderate mechanical strength have potential applications in artificial muscle, soft actuators and drug release, to name a few. Full article

(This article belongs to the Section Materials Physics)

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19 pages, 3402 KiB

Open AccessEditor’s ChoicePerspective

LIPSS Applied to Wide Bandgap Semiconductors and Dielectrics: Assessment and Future Perspectives

by Matteo Mastellone, Maria Lucia Pace, Mariangela Curcio, Nicola Caggiano, Angela De Bonis, Roberto Teghil, Patrizia Dolce, Donato Mollica, Stefano Orlando, Antonio Santagata, Valerio Serpente, Alessandro Bellucci, Marco Girolami, Riccardo Polini and Daniele Maria Trucchi

Materials 2022, 15(4), 1378; https://doi.org/10.3390/ma15041378 - 13 Feb 2022

Cited by 30 | Viewed by 4627

Abstract

With the aim of presenting the processes governing the Laser-Induced Periodic Surface Structures (LIPSS), its main theoretical models have been reported. More emphasis is given to those suitable for clarifying the experimental structures observed on the surface of wide bandgap semiconductors (WBS) and [...] Read more.

With the aim of presenting the processes governing the Laser-Induced Periodic Surface Structures (LIPSS), its main theoretical models have been reported. More emphasis is given to those suitable for clarifying the experimental structures observed on the surface of wide bandgap semiconductors (WBS) and dielectric materials. The role played by radiation surface electromagnetic waves as well as Surface Plasmon Polaritons in determining both Low and High Spatial Frequency LIPSS is briefly discussed, together with some experimental evidence. Non-conventional techniques for LIPSS formation are concisely introduced to point out the high technical possibility of enhancing the homogeneity of surface structures as well as tuning the electronic properties driven by point defects induced in WBS. Among these, double- or multiple-fs-pulse irradiations are shown to be suitable for providing further insight into the LIPSS process together with fine control on the formed surface structures. Modifications occurring by LIPSS on surfaces of WBS and dielectrics display high potentialities for their cross-cutting technological features and wide applications in which the main surface and electronic properties can be engineered. By these assessments, the employment of such nanostructured materials in innovative devices could be envisaged. Full article

(This article belongs to the Special Issue New Advances in Low-Dimensional Materials and Nanostructures)

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10 pages, 4102 KiB

Open AccessEditor’s ChoiceArticle

Face Mask Wastes as Cementitious Materials: A Possible Solution to a Big Concern

by Marta Castellote, Eva Jiménez-Relinque, María Grande, Francisco J. Rubiano and Ángel Castillo

Materials 2022, 15(4), 1371; https://doi.org/10.3390/ma15041371 - 12 Feb 2022

Cited by 24 | Viewed by 8573

Abstract

After more than two years wearing surgical masks due to the COVID-19 pandemic, used masks have become a significant risk for ecosystems, as they are producing wastes in huge amounts. They are a potential source of disturbance by themselves and as microplastic contamination [...] Read more.

After more than two years wearing surgical masks due to the COVID-19 pandemic, used masks have become a significant risk for ecosystems, as they are producing wastes in huge amounts. They are a potential source of disturbance by themselves and as microplastic contamination in the water system. As 5500 tons of face masks are estimated to be used each year, there is an urgent need to manage them according to the circular economy principles and avoid their inadequate disposal. In this paper, surgical wear masks (WM), without any further pretreatment, have been introduced as addition to mortars up to 5% in the weight of cement. Mechanical and microstructural characterization have been carried out. The results indicate that adding MW to the cement supposes a decrease in the properties of the material, concerning both strength and durability behavior. However, even adding a 5% of WM in weight of cement, the aspect of the mortars is quite good, the flexural strength is not significantly affected, and the strength and durability parameters are maintained at levels that—even lower than the reference—are quite reasonable for use. Provided that the worldwide production of cement is around 4.1 Bt/year, the introduction of a 5% of WM in less than 1% of the cement produced, would make it possible to get rid of the mask waste being produced. Full article

(This article belongs to the Special Issue Sustainability in Construction and Building Materials)

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26 pages, 7881 KiB

Open AccessEditor’s ChoiceArticle

Cathodic Protection of Mild Steel Using Aluminium-Based Alloys

by Maria del Rosario Silva Campos, Carsten Blawert, Nico Scharnagl, Michael Störmer and Mikhail L. Zheludkevich

Materials 2022, 15(4), 1301; https://doi.org/10.3390/ma15041301 - 10 Feb 2022

Cited by 31 | Viewed by 5249

Abstract

Typically, steel is protected from corrosion by employing sacrificial anodes or coatings based on Zn, Mg, Al or Cd. However, stricter environmental regulations require new environmentally friendly alternatives to replace Cd. Traditionally, Al-based anodes have been employed to cathodically protect steel in marine [...] Read more.

Typically, steel is protected from corrosion by employing sacrificial anodes or coatings based on Zn, Mg, Al or Cd. However, stricter environmental regulations require new environmentally friendly alternatives to replace Cd. Traditionally, Al-based anodes have been employed to cathodically protect steel in marine applications or as ion vapour deposition (IVD)-Al sacrificial coatings for aerospace applications. However, Al tends to passivate, thus losing its protective effect. Therefore, it is important to identify possible alloys that can provide a constantly sufficient current. In this study, Al-X alloys (X = Ag, Bi, Ca, Cr, Cu, Ga, Gd, In, Mg, Mn, Ni, Sb, Si, Sn, V, Ti, Zn and Zr) were firstly tested for a screening of the sacrificial properties of binary systems. Al-0.5Cr, Al-1Sn, Al-0.2Ga, Al-0.1In, Al-2Si and Al-5Zn alloys were suggested as promising sacrificial Al-based alloys. Suitable heat treatments for each system were implemented to reduce the influence of the secondary phases on the corrosion properties by minimising localised attack. extensive evaluation of the corrosion properties, including galvanic coupling of these alloys to steel, was performed in the NaCl electrolyte. A comparative analysis was conducted in order to choose the most promising alloy(s) for avoiding the passivation of Al and for efficient cathodic protection to steel. Full article

(This article belongs to the Section Corrosion)

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15 pages, 17149 KiB

Open AccessEditor’s ChoiceArticle

Improving the Thermomechanical Properties of Poly(lactic acid) via Reduced Graphene Oxide and Bioderived Poly(decamethylene 2,5-furandicarboxylate)

by Giulia Fredi, Mahdi Karimi Jafari, Andrea Dorigato, Dimitrios N. Bikiaris and Alessandro Pegoretti

Materials 2022, 15(4), 1316; https://doi.org/10.3390/ma15041316 - 10 Feb 2022

Cited by 12 | Viewed by 3243

Abstract

Polylactide (PLA) is the most widely used biopolymer, but its poor ductility and scarce gas barrier properties limit its applications in the packaging field. In this work, for the first time, the properties of PLA solvent-cast films are improved by the addition of [...] Read more.

Polylactide (PLA) is the most widely used biopolymer, but its poor ductility and scarce gas barrier properties limit its applications in the packaging field. In this work, for the first time, the properties of PLA solvent-cast films are improved by the addition of a second biopolymer, i.e., poly(decamethylene 2,5-furandicarboxylate) (PDeF), added in a weight fraction of 10 wt%, and a carbon-based nanofiller, i.e., reduced graphene oxide (rGO), added in concentrations of 0.25–2 phr. PLA and PDeF are immiscible, as evidenced by scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) spectroscopy, with PDeF spheroidal domains showing poor adhesion to PLA. The addition of 0.25 phr of rGO, which preferentially segregates in the PDeF domains, makes them smaller and considerably rougher and improves the interfacial interaction. Differential scanning calorimetry (DSC) confirms the immiscibility of the two polymer phases and highlights that rGO enhances the crystallinity of both polymer phases (especially of PDeF). Thermogravimetric analysis (TGA) highlights the positive impact of rGO and PDeF on the thermal degradation resistance of PLA. Quasi-static tensile tests evidence that adding 10 wt% of PDeF and a small fraction of rGO (0.25 phr) to PLA considerably enhances the strain at break, which raises from 5.3% of neat PLA to 10.0% by adding 10 wt% of PDeF, up to 75.8% by adding also 0.25 phr of rGO, thereby highlighting the compatibilizing role of rGO on this blend. On the other hand, a further increase in rGO concentration decreases the strain at break due to agglomeration but enhances the mechanical stiffness and strength up to an rGO concentration of 1 phr. Overall, these results highlight the positive and synergistic contribution of PDeF and rGO in enhancing the thermomechanical properties of PLA, and the resulting nanocomposites are promising for packaging applications. Full article

(This article belongs to the Special Issue Green Composites: Challenges and Opportunities)

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23 pages, 6027 KiB

Open AccessEditor’s ChoiceArticle

A Ternary Seismic Metamaterial for Low Frequency Vibration Attenuation

by Chen Chen, Jincheng Lei and Zishun Liu

Materials 2022, 15(3), 1246; https://doi.org/10.3390/ma15031246 - 8 Feb 2022

Cited by 26 | Viewed by 3608

Abstract

Structural vibration induced by low frequency elastic waves presents a great threat to infrastructure such as buildings, bridges, and nuclear structures. In order to reduce the damage of low frequency structural vibration, researchers proposed the structure of seismic metamaterial, which can be used [...] Read more.

Structural vibration induced by low frequency elastic waves presents a great threat to infrastructure such as buildings, bridges, and nuclear structures. In order to reduce the damage of low frequency structural vibration, researchers proposed the structure of seismic metamaterial, which can be used to block the propagation of low frequency elastic wave by adjusting the frequency range of elastic wave propagation. In this study, based on the concept of phononic crystal, a ternary seismic metamaterial is proposed to attenuate low frequency vibration by generating band gaps. The proposed metamaterial structure is periodically arranged by cube units, which consist of rubber coating, steel scatter, and soft matrix (like soil). The finite element analysis shows that the proposed metamaterial structure has a low frequency band gap with 8.5 Hz bandwidth in the range of 0–20 Hz, which demonstrates that the metamaterial can block the elastic waves propagation in a fairly wide frequency range within 0–20 Hz. The frequency response analysis demonstrates that the proposed metamaterial can effectively attenuate the low frequency vibration. A simplified equivalent mass–spring model is further proposed to analyze the band gap range which agrees well with the finite element results. This model provides a more convenient method to calculate the band gap range. Combining the proposed equivalent mass–spring model with finite element analysis, the effect of material parameters and geometric parameters on the band gap characteristic is investigated. This study can provide new insights for low frequency vibration attenuation. Full article

(This article belongs to the Section Mechanics of Materials)

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15 pages, 7332 KiB

Open AccessEditor’s ChoiceArticle

Strain Rate and Stress Amplitude Effects on the Mechanical Behavior of Carbon Paste Used in the Hall–Héroult Process and Subjected to Cyclic Loadings

by Zahraa Kansoun, Hicham Chaouki, Donald Picard, Julien Lauzon-Gauthier, Houshang Alamdari and Mario Fafard

Materials 2022, 15(3), 1263; https://doi.org/10.3390/ma15031263 - 8 Feb 2022

Cited by 4 | Viewed by 1868

Abstract

Carbon products such as anodes and ramming paste must have well-defined physical, mechanical, chemical, and electrical properties to perform their functions effectively in the aluminum electrolysis cell. The physical and mechanical properties of these products are assigned during the shaping procedure in which [...] Read more.

Carbon products such as anodes and ramming paste must have well-defined physical, mechanical, chemical, and electrical properties to perform their functions effectively in the aluminum electrolysis cell. The physical and mechanical properties of these products are assigned during the shaping procedure in which compaction stresses are applied to the green carbon paste. The optimization of the shaping process is crucial to improving the properties of the carbon products and consequently to increasing the energy efficiency and decreasing the greenhouse gas emissions of the Hall–Héroult process. The objective of this study is to experimentally investigate the effect(s) of the strain rate, of the stress maximum amplitude, and of the unloading level on the behavior of a green carbon paste subjected to cyclic loading. To this end, experiments consisting of (1) cyclic compaction tests at different maximum stress amplitudes and strain rates, and (2) cyclic compaction tests with different unloading levels were carried out. The study obtained the following findings about the behavior of carbon paste subjected to cyclic loads. The strain rate in the studied range had no effect either on the evolution of the permanent strain as a function of the cycle number, nor on the shape of the stress–strain hysteresis during the cyclic loading. Moreover, samples of the same density that had been subjected to different maximum stress amplitudes in their loading history did not have the same shape of the stress–strain curve. On the other hand, despite having different densities, samples subjected to the same number of cycles produce the same stress–strain curve during loading even though they were subjected to different maximum stress amplitudes in their loading histories. Finally, the level of unloading during each cycle of a cyclic test proved significant; when the sample was unloaded to a lower level of stress during each cycle, the permanent strain as a function of the cycle number was higher. Full article

(This article belongs to the Section Carbon Materials)

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17 pages, 6845 KiB

Open AccessEditor’s ChoiceArticle

Effect of Loading Rate and Initial Strain on Seismic Performance of an Innovative Self-Centering SMA Brace

by Yigang Jia, Bo Zhang, Sizhi Zeng, Fenghua Tang, Shujun Hu and Wenping Chen

Materials 2022, 15(3), 1234; https://doi.org/10.3390/ma15031234 - 7 Feb 2022

Cited by 10 | Viewed by 2215

Abstract

In order to improve the energy dissipation capacity and to reduce the residual deformation of civil structures simultaneously, this paper puts forwards an innovative self-centering shape memory alloy (SMA) brace that is based on the design concepts of SMA’s superelasticity and low friction [...] Read more.

In order to improve the energy dissipation capacity and to reduce the residual deformation of civil structures simultaneously, this paper puts forwards an innovative self-centering shape memory alloy (SMA) brace that is based on the design concepts of SMA’s superelasticity and low friction slip. Seven self-centering SMA brace specimens were tested under cyclic loading, and the hysteresis curves, bond curves, secant stiffness, energy dissipation coefficient, equivalent damping coefficient, and the self-centering capacity ratio of these specimens were investigated, allowing us to provide an evaluation of the effects of the loading rate and initial strain on the seismic performance. The test results show that the self-centering SMA braces have an excellent energy dissipation capacity, bearing capacity, and self-centering capacity, while the steel plates remain elastic, and the SMA in the specimens that are always under tension are able to return to the initial state. The hysteresis curves of all of the specimens are idealized as a flag shape with low residual deformation, and the self-centering capacity ratio reached 89.38%. In addition, both the loading rate and the initial strain were shown to have a great influence on the seismic performance of the self-centering SMA brace. The improved numerical models combined with the Graesser model and Bouc–Wen model in MATLAB were used to simulate the seismic performance of the proposed braces with different loading rates and initial strains, and the numerical results are consistent with the test results under the same conditions, meaning that they can accurately predict the seismic performance of the self-centering SMA brace proposed here. Full article

(This article belongs to the Special Issue Shape Memory Alloys for Civil Engineering)

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29 pages, 9696 KiB

Open AccessEditor’s ChoiceArticle

The Use of a High-Pressure Water-Ice Jet for Removing Worn Paint Coating in Renovation Process

by Grzegorz Chomka, Jarosław Chodór, Leon Kukiełka and Maciej Kasperowicz

Materials 2022, 15(3), 1168; https://doi.org/10.3390/ma15031168 - 3 Feb 2022

Cited by 4 | Viewed by 2722

Abstract

The paper presents the results of investigations into the possibility of using ahigh-pressure water-ice jet as a new method for removing a worn-out paint coating from the surface of metal parts (including those found in means of transportation) and for preparing the base [...] Read more.

The paper presents the results of investigations into the possibility of using ahigh-pressure water-ice jet as a new method for removing a worn-out paint coating from the surface of metal parts (including those found in means of transportation) and for preparing the base surface for the application of renovation paint coating. Experimental investigations were carried out in four stages, on flat specimens, sized S × H = 75 × 115 mm, cut from sheet metal made of various materials such as steel X5CrNi18-10, PA2 aluminium alloy and PMMA polymethyl methacrylate (plastic). In the first stage, the surfaces of the samples were subjected to observation of surface morphology under a scanning electron microscope, and surface topography (ST) measurements were made on a profilographometer. Two ST parameters were analysed in detail: the maximum height of surface roughness Sz and the arithmetic mean surface roughness Sa. Next, paint coatings were applied to the specimens as a base. In the third stage, the paint coating applied was removed by means of a high-pressure water-ice jet (HPWIJ) by changing the values of the technological parameters, i.e., water jet pressure p_w, dry ice mass flow rate

{\dot{m}}_{L}

, distance between the sprinkler head outlet and the surface being treated (the so-called working jet length) l₂ and spray angle κ for the following constants: the number of TS = 4 holes, water hole diameter φ = 1.2 mm and sprinkler head length L_k = 200 mm. Afterwards, the surface morphology was observed again and the surface topography of the specimen was investigated by measuring selected 3D parameters of the ST structure, Sz and Sa. The results of investigations into the influence of selected HPWIJ treatment parameters on the surface Q_F removal efficiency obtained are also presented. Univariate regression functions were developed for the mean stripping efficiency based on the following: dry ice mass flow rate

{\dot{m}}_{L}

, working jet length l₂ and spray angle κ. Based on these functions, the values of optimal parameters were determined that allow the maximum efficiency of the process to be obtained. A 95% confidence region for the regression function was also developed. The results demonstrated that HPWIJ treatment does not interfere with the geometric structure of the base material, and they confirmed the possibility of using this treatment as an efficient method of removing a worn paint layer from bases made of various metal and plastic materials, and preparing it for applying a new layer during renovation. Full article

(This article belongs to the Special Issue Feature Papers in Materials Simulation and Design)

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33 pages, 7644 KiB

Open AccessEditor’s ChoiceReview

Application of Graphene-Related Materials in Organic Solar Cells

by Lara Velasco Davoise, Ana M. Díez-Pascual and Rafael Peña Capilla

Materials 2022, 15(3), 1171; https://doi.org/10.3390/ma15031171 - 3 Feb 2022

Cited by 32 | Viewed by 5219

Abstract

Graphene-related materials (GRMs) such as graphene quantum dots (GQDs), graphene oxide (GO), reduced graphene oxide (rGO), graphene nanoribbons (GNRs), and so forth have recently emerged as photovoltaic (PV) materials due to their nanodimensional structure and outstanding properties such as high electrical and thermal [...] Read more.

Graphene-related materials (GRMs) such as graphene quantum dots (GQDs), graphene oxide (GO), reduced graphene oxide (rGO), graphene nanoribbons (GNRs), and so forth have recently emerged as photovoltaic (PV) materials due to their nanodimensional structure and outstanding properties such as high electrical and thermal conductivity, large specific surface, and unique combination of mechanical strength and flexibility. They can be a crucial part of transparent electrodes, hole/electron transport materials, and active layers in organic solar cells (OSCs). Besides their role in charge extraction and transport, GRMs act as device protectors against environmental degradation through their compact bidimensional structure and offer good durability. This review briefly presents the synthesis methods of GRMs and describes the current progress in GRM-based OSCs. PV parameters (short circuit current, open circuit voltage, power conversion efficiency, and fill factor) are summarized and comparatively discussed for the different structures. The efficiency recently surpassed 15% for an OSC incorporating polymer-modified graphene as a transparent electrode. The long-term stability of OSCs incorporating GRMs is also discussed. Finally, conclusions and the outlook for future investigation into GRM-based devices for PVs are presented. Full article

(This article belongs to the Special Issue Advanced Materials for Photonics and Photovoltaics Applications)

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26 pages, 8120 KiB

Open AccessEditor’s ChoiceReview

by Zeyu Chi, Jacob J. Asher, Michael R. Jennings, Ekaterine Chikoidze and Amador Pérez-Tomás

Materials 2022, 15(3), 1164; https://doi.org/10.3390/ma15031164 - 2 Feb 2022

Cited by 49 | Viewed by 9440

Abstract

Currently, a significant portion (~50%) of global warming emissions, such as CO₂, are related to energy production and transportation. As most energy usage will be electrical (as well as transportation), the efficient management of electrical power is thus central to achieve [...] Read more.

Currently, a significant portion (~50%) of global warming emissions, such as CO₂, are related to energy production and transportation. As most energy usage will be electrical (as well as transportation), the efficient management of electrical power is thus central to achieve the XXI century climatic goals. Ultra-wide bandgap (UWBG) semiconductors are at the very frontier of electronics for energy management or energy electronics. A new generation of UWBG semiconductors will open new territories for higher power rated power electronics and solar-blind deeper ultraviolet optoelectronics. Gallium oxide—Ga₂O₃ (4.5–4.9 eV), has recently emerged pushing the limits set by more conventional WBG (~3 eV) materials, such as SiC and GaN, as well as for transparent conducting oxides (TCO), such asIn₂O₃, ZnO and SnO₂, to name a few. Indeed, Ga₂O₃ as the first oxide used as a semiconductor for power electronics, has sparked an interest in oxide semiconductors to be investigated (oxides represent the largest family of UWBG). Among these new power electronic materials, Al_xGa_1-xO₃ may provide high-power heterostructure electronic and photonic devices at bandgaps far beyond all materials available today (~8 eV) or ZnGa₂O₄ (~5 eV), enabling spinel bipolar energy electronics for the first time ever. Here, we review the state-of-the-art and prospects of some ultra-wide bandgap oxide semiconductor arising technologies as promising innovative material solutions towards a sustainable zero emission society. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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22 pages, 42069 KiB

Open AccessEditor’s ChoiceArticle

Investigation of an Impedimetric LaSrMnO₃-Au/Y₂O₃-ZrO₂-Al₂O₃ Composite NO_x Sensor

by Nabamita Pal, Gaurab Dutta, Khawlah Kharashi and Erica P. Murray

Materials 2022, 15(3), 1165; https://doi.org/10.3390/ma15031165 - 2 Feb 2022

Cited by 8 | Viewed by 3910

Abstract

Composite NO_x sensors were fabricated by combining partially and fully stabilized yttria-doped zirconia with alumina forming a composite electrolyte, Y₂O₃-ZrO₂-Al₂O₃, and strontium-doped lanthanum manganese oxide mixed with gold to form the composite [...] Read more.

Composite NO_x sensors were fabricated by combining partially and fully stabilized yttria-doped zirconia with alumina forming a composite electrolyte, Y₂O₃-ZrO₂-Al₂O₃, and strontium-doped lanthanum manganese oxide mixed with gold to form the composite sensing electrode, La_0.8 Sr_0.2MnO₃-Au. A surface chemistry analysis of the composite sensor was conducted to interpret defects and the structural phases present at the Y₂O₃-ZrO₂-Al₂O₃ electrolyte, as well as the charge conduction mechanism at the LaSrMnO₃-Au electrode surface. Based on the surface chemistry analysis, ionic and electronic transport properties, and microstructural features of sensor components, the working principle was described for NO_x sensing at the composite sensor. The role of the composite materials on the NO_x sensing response, cross-sensitivity to O₂, H₂O, CO, CO₂, and CH₄, and the response/recovery rates relative to sensor accuracy were characterized by operating the composite

{NO}_{x}

sensors via the impedimetric method. The composite sensors were operated at temperatures ranging from 575 to 675 °C in dry and humidified gas environments with NO and NO₂ concentrations varying from 0 to 100 ppm, where the balance gas was N₂. It was found that the microstructure of the composite NO_x sensor electrolyte and sensing electrode had a significant effect on interfacial reactions at the triple phase boundary, as well as the density of active sites for oxygen reactions. Overall, the composite NO_x sensor microstructure enabled a high NO_x sensing response, along with low cross-sensitivity to O₂, CO, CO₂, and CH₄, and promoted NO detection down to 2 ppm. Full article

(This article belongs to the Section Advanced Composites)

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16 pages, 3925 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Efficiency of Thermoelectric Personal Cooling System Based on Utility Tests

by Anna Dąbrowska, Monika Kobus, Łukasz Starzak and Bartosz Pękosławski

Materials 2022, 15(3), 1115; https://doi.org/10.3390/ma15031115 - 31 Jan 2022

Cited by 6 | Viewed by 4010

Abstract

Thermoelectric modules can find practical application in clothing with a cooling function. A personal cooling system using Peltier modules integrated with clothing was developed and tested with the participation of a person. A dedicated electronic controller was designed that enabled the power or [...] Read more.

Thermoelectric modules can find practical application in clothing with a cooling function. A personal cooling system using Peltier modules integrated with clothing was developed and tested with the participation of a person. A dedicated electronic controller was designed that enabled the power or temperature to be controlled and recorded. In the research, the influence of heat sinks and the method of controlling the operation of the module on the cooling efficiency was assessed. The research was aimed at selecting the operating mode of the controller and choosing the arrangement of modules comparing cooling efficiency. The research showed that by selection of appropriate controlling mode, the electric power used can be reduced while keeping the cooling efficiency at the same level. The location of Peltier modules in places where they can tightly adhere to the body increases their performance. Full article

(This article belongs to the Special Issue Smart Fabrics and Intelligent Textiles)

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22 pages, 9161 KiB

Open AccessEditor’s ChoiceArticle

Biodegradable Thermoplastic Starch/Polycaprolactone Blends with Co-Continuous Morphology Suitable for Local Release of Antibiotics

by Veronika Gajdosova, Beata Strachota, Adam Strachota, Danuse Michalkova, Sabina Krejcikova, Petr Fulin, Otakar Nyc, Adam Brinek, Marek Zemek and Miroslav Slouf

Materials 2022, 15(3), 1101; https://doi.org/10.3390/ma15031101 - 30 Jan 2022

Cited by 13 | Viewed by 3199

Abstract

We report a reproducible preparation and characterization of highly homogeneous thermoplastic starch/pol(ε-caprolactone) blends (TPS/PCL) with a minimal thermomechanical degradation and co-continuous morphology. These materials would be suitable for biomedical applications, specifically for the local release of antibiotics (ATB) from the TPS phase. The [...] Read more.

We report a reproducible preparation and characterization of highly homogeneous thermoplastic starch/pol(ε-caprolactone) blends (TPS/PCL) with a minimal thermomechanical degradation and co-continuous morphology. These materials would be suitable for biomedical applications, specifically for the local release of antibiotics (ATB) from the TPS phase. The TPS/PCL blends were prepared in the whole concentration range. In agreement with theoretical predictions based on component viscosities, the co-continuous morphology was found for TPS/PCL blends with a composition of 70/30 wt.%. The minimal thermomechanical degradation of the blends was achieved by an optimization of the processing conditions and by keeping processing temperatures as low as possible, because higher temperatures might damage ATB in the final application. The blends’ homogeneity was verified by scanning electron microscopy. The co-continuous morphology was confirmed by submicron-computed tomography. The mechanical performance of the blends was characterized in both microscale (by an instrumented microindentation hardness testing; MHI) and macroscale (by dynamic thermomechanical analysis; DMTA). The elastic moduli of TPS increased ca four times in the TPS/PCL (70/30) blend. The correlations between elastic moduli measured by MHI and DMTA were very strong, which implied that, in the future studies, it would be possible to use just micromechanical testing that does not require large specimens. Full article

(This article belongs to the Special Issue Relations between Structure, Micro- and Nanomechanical Properties of Materials)

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11 pages, 2707 KiB

Open AccessEditor’s ChoiceArticle

Radiative Thermal Effects in Large Scale Additive Manufacturing of Polymers: Numerical and Experimental Investigations

by Benoît Cosson, André Chateau Akué Asséko, Lukas Pelzer and Christian Hopmann

Materials 2022, 15(3), 1052; https://doi.org/10.3390/ma15031052 - 29 Jan 2022

Cited by 2 | Viewed by 2150

Abstract

The present paper addresses experimental and numerical investigations of a Large Scale Additive Manufacturing (LSAM) process using polymers. By producing large components without geometrical constraints quickly and economically, LSAM processes have the capability to revolutionize many industries. Accurate prediction and control of the [...] Read more.

The present paper addresses experimental and numerical investigations of a Large Scale Additive Manufacturing (LSAM) process using polymers. By producing large components without geometrical constraints quickly and economically, LSAM processes have the capability to revolutionize many industries. Accurate prediction and control of the thermal history is key for a successful manufacturing process and for achieving high quality and good mechanical properties of the manufactured part. During the LSAM process, the heat emitted by the nozzle leads to an increase in the temperature of the previously deposited layer, which prepares the surface for better adhesion of the new layer. It is therefore necessary to take into account this part of heat source in the transient heat transfer equation to correctly and completely describe the process and predict the temperature field of the manufactured part. The present study contributes to experimental investigations and numerical analysis during the LSAM process. During the process, two types of measurements are performed: firstly, the heat emitted by the nozzle is measured via a radiative heat sensor; secondly, the temperature field is measured using an infrared camera while varying the process speed. At the same time, a numerical simulation model is developed in order to validate the experimental results. The temperature fields of the manufactured parts computed by numerical simulations are in very good agreement with the temperature fields measured by infrared thermograph with the contribution of the nozzle’s heat exchange. Full article

(This article belongs to the Special Issue Fusion Bonding/Welding of Polymer Composites)

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18 pages, 2086 KiB

Open AccessEditor’s ChoiceArticle

Influence of the hBN Dielectric Layers on the Quantum Transport Properties of MoS₂ Transistors

by Sara Fiore, Cedric Klinkert, Fabian Ducry, Jonathan Backman and Mathieu Luisier

Materials 2022, 15(3), 1062; https://doi.org/10.3390/ma15031062 - 29 Jan 2022

Cited by 6 | Viewed by 4923

Abstract

The encapsulation of single-layer 2D materials within hBN has been shown to improve the mobility of these compounds. Nevertheless, the interplay between the semiconductor channel and the surrounding dielectrics is not yet fully understood, especially their electron–phonon interactions. Therefore, here, we present an [...] Read more.

The encapsulation of single-layer 2D materials within hBN has been shown to improve the mobility of these compounds. Nevertheless, the interplay between the semiconductor channel and the surrounding dielectrics is not yet fully understood, especially their electron–phonon interactions. Therefore, here, we present an ab initio study of the coupled electrons and phonon transport properties of MoS

_{2}

-hBN devices. The characteristics of two transistor configurations are compared to each other: one where hBN is treated as a perfectly insulating, non-vibrating layer and one where it is included in the ab initio domain as MoS

_{2}

. In both cases, a reduction of the ON-state current by about 50% is observed as compared to the quasi-ballistic limit. Despite the similarity in the current magnitude, explicitly accounting for hBN leads to additional electron–phonon interactions at frequencies corresponding to the breathing mode of the MoS

_{2}

-hBN system. Moreover, the presence of an hBN layer around the 2D semiconductor affects the Joule-induced temperature distribution within the transistor. Full article

(This article belongs to the Special Issue Modeling of Advanced Metal-Oxide-Semiconductor Devices)

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15 pages, 3291 KiB

Open AccessEditor’s ChoiceArticle

Electronic and Optical Properties of InAs QDs Grown by MBE on InGaAs Metamorphic Buffer

by Paweł Wyborski, Paweł Podemski, Piotr Andrzej Wroński, Fauzia Jabeen, Sven Höfling and Grzegorz Sęk

Materials 2022, 15(3), 1071; https://doi.org/10.3390/ma15031071 - 29 Jan 2022

Cited by 8 | Viewed by 3437

Abstract

We present the optical characterization of GaAs-based InAs quantum dots (QDs) grown by molecular beam epitaxy on a digitally alloyed InGaAs metamorphic buffer layer (MBL) with gradual composition ensuring a redshift of the QD emission up to the second telecom window. Based on [...] Read more.

We present the optical characterization of GaAs-based InAs quantum dots (QDs) grown by molecular beam epitaxy on a digitally alloyed InGaAs metamorphic buffer layer (MBL) with gradual composition ensuring a redshift of the QD emission up to the second telecom window. Based on the photoluminescence (PL) measurements and numerical calculations, we analyzed the factors influencing the energies of optical transitions in QDs, among which the QD height seems to be dominating. In addition, polarization anisotropy of the QD emission was observed, which is a fingerprint of significant valence states mixing enhanced by the QD confinement potential asymmetry, driven by the decreased strain with increasing In content in the MBL. The barrier-related transitions were probed by photoreflectance, which combined with photoluminescence data and the PL temperature dependence, allowed for the determination of the carrier activation energies and the main channels of carrier loss, identified as the carrier escape to the MBL barrier. Eventually, the zero-dimensional character of the emission was confirmed by detecting the photoluminescence from single QDs with identified features of the confined neutral exciton and biexciton complexes via the excitation power and polarization dependences. Full article

(This article belongs to the Special Issue Optical Properties and Application Prospects of Novel Epitaxial Nanostructures)

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16 pages, 2447 KiB

Open AccessEditor’s ChoiceArticle

Dimensionality of the Superconductivity in the Transition Metal Pnictide WP

by Angela Nigro, Giuseppe Cuono, Pasquale Marra, Antonio Leo, Gaia Grimaldi, Ziyi Liu, Zhenyu Mi, Wei Wu, Guangtong Liu, Carmine Autieri, Jianlin Luo and Canio Noce

Materials 2022, 15(3), 1027; https://doi.org/10.3390/ma15031027 - 28 Jan 2022

Cited by 5 | Viewed by 3380

Abstract

We report theoretical and experimental results on the transition metal pnictide WP. The theoretical outcomes based on tight-binding calculations and density functional theory indicate that WP is a three-dimensional superconductor with an anisotropic electronic structure and nonsymmorphic symmetries. On the other hand, magnetoresistance [...] Read more.

We report theoretical and experimental results on the transition metal pnictide WP. The theoretical outcomes based on tight-binding calculations and density functional theory indicate that WP is a three-dimensional superconductor with an anisotropic electronic structure and nonsymmorphic symmetries. On the other hand, magnetoresistance experimental data and the analysis of superconducting fluctuations of the conductivity in external magnetic field indicate a weakly anisotropic three-dimensional superconducting phase. Full article

(This article belongs to the Special Issue Challenges and Opportunities of Superconducting Materials for Future Applications)

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15 pages, 4035 KiB

Open AccessEditor’s ChoiceArticle

Superhydrophobic Coating Based on Porous Aluminum Oxide Modified by Polydimethylsiloxane (PDMS)

by Klaudia Olkowicz, Zofia Buczko, Barbara Nasiłowska, Kamil Kowalczyk and Joanna Czwartos

Materials 2022, 15(3), 1042; https://doi.org/10.3390/ma15031042 - 28 Jan 2022

Cited by 13 | Viewed by 4295

Abstract

The aim of this study was to obtain a superhydrophobic coating by modifying anodized aluminum using polydimethylsiloxane (PDMS). In order to obtain a superhydrophobic coating on an aluminum substrate, a multistage treatment was implemented. Specimens of aluminum were treated by abrasive blasting, anodization [...] Read more.

The aim of this study was to obtain a superhydrophobic coating by modifying anodized aluminum using polydimethylsiloxane (PDMS). In order to obtain a superhydrophobic coating on an aluminum substrate, a multistage treatment was implemented. Specimens of aluminum were treated by abrasive blasting, anodization in sulfuric acid, impregnation by PDMS, rinsing in toluene to remove excess of PDMS, and curing. A rough surface with an additional low free energy layer on it resulted in a superhydrophobic effect. The coating obtained has an average contact angle of 159°. The specimens were tested in terms of durability in natural conditions. Additionally, anti-icing and anti-fouling properties were evaluated. The coating was compared with anodized aluminum obtained by a basic process. Full article

(This article belongs to the Special Issue Advances in the Fabrication of Superhydrophobic Polymeric Surfaces)

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15 pages, 1640 KiB

Open AccessEditor’s ChoiceArticle

Influence of the Fly Ash Content on the Fresh and Hardened Properties of Alkali-Activated Slag Pastes with Admixtures

by María Jimena de Hita and María Criado

Materials 2022, 15(3), 992; https://doi.org/10.3390/ma15030992 - 27 Jan 2022

Cited by 15 | Viewed by 2962

Abstract

A study on the influence of the inclusion of slag or fly ash and five types of superplasticizers on the fresh and hardened properties of alkali-activated cements is presented. Three alkali-activated slag formulations with different fly ash content (0, 15, and 30%) in [...] Read more.

A study on the influence of the inclusion of slag or fly ash and five types of superplasticizers on the fresh and hardened properties of alkali-activated cements is presented. Three alkali-activated slag formulations with different fly ash content (0, 15, and 30%) in the presence of five admixtures (vinyl copolymer, melamine, and three polycarboxylates with different chain lengths) were assessed for fluidity control and setting adjustment without loss of mechanical properties. Solid sodium metasilicate was used as an alkaline activator. Their fresh and hardened properties were studied through slump, setting time, isothermal calorimetry, mechanical strengths, and porosity tests. The results showed that the increase of fly ash content delayed the reaction and improved workability but reduced compressive strengths. Concerning the admixtures, these maintained fluidity especially for the one based on polycarboxylate with very long chains. The melamine and polycarboxylate with very long chain admixtures did not have a drastic impact on mechanical properties at early ages; even a gain of flexural and compressive strength was noted. Full article

(This article belongs to the Special Issue Alkali Activated Materials and Ceramics: Synthesis, Properties and Applications)

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13 pages, 5229 KiB

Open AccessEditor’s ChoiceArticle

Corrosion Behavior of Ultrafine-Grained CoCrFeMnNi High-Entropy Alloys Fabricated by High-Pressure Torsion

by Haruka Shimizu, Motohiro Yuasa, Hiroyuki Miyamoto and Kaveh Edalati

Materials 2022, 15(3), 1007; https://doi.org/10.3390/ma15031007 - 27 Jan 2022

Cited by 25 | Viewed by 3657

Abstract

The influence of the nanocrystalline structure produced by severe plastic deformation (SPD) on the corrosion behavior of CoCrFeMnNi alloys with Cr contents ranging from 0 to 20 at.% was investigated in aqueous 0.5 M H₂SO₄ and 3.5% NaCl solutions. The [...] Read more.

The influence of the nanocrystalline structure produced by severe plastic deformation (SPD) on the corrosion behavior of CoCrFeMnNi alloys with Cr contents ranging from 0 to 20 at.% was investigated in aqueous 0.5 M H₂SO₄ and 3.5% NaCl solutions. The resistance to general corrosion and pitting became higher in both the solutions, with higher passivation capability observed with increasing Cr content, and it is believed that the high corrosion resistance of CoCrFeMnNi alloys can be attributed to the incorporation of the Cr element. However, the impact of the nanocrystalline structure produced by SPD on the corrosion behavior was negligibly small. This is inconsistent with reports on nanocrystalline binary Fe–Cr alloys and stainless steels processed by SPD, where grain refinement by SPD results in higher corrosion resistance. The small change in the corrosion behavior with respect to grain refinement is discussed, based on the passivation process of Fe–Cr alloys and on the influence of the core effects of HEAs on the passivation process. Full article

(This article belongs to the Special Issue Corrosion and Corrosion Inhibition of Metals and Their Alloys)

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16 pages, 5082 KiB

Open AccessEditor’s ChoiceArticle

Changes in the Properties in Bimodal Mg Alloy Bars Obtained for Various Deformation Patterns in the RSR Rolling Process

by Andrzej Stefanik, Piotr Szota, Sebastian Mróz and Marcin Wachowski

Materials 2022, 15(3), 954; https://doi.org/10.3390/ma15030954 - 26 Jan 2022

Cited by 7 | Viewed by 2369

Abstract

The paper presents the theoretical and experimental research conducted to date regarding the possibility of obtaining round bars from AZ31 magnesium alloy with a bimodal structure rolled in the radial shear rolling process (RSR) technology. There is no analysis of the impact of [...] Read more.

The paper presents the theoretical and experimental research conducted to date regarding the possibility of obtaining round bars from AZ31 magnesium alloy with a bimodal structure rolled in the radial shear rolling process (RSR) technology. There is no analysis of the impact of the deformation path (distribution of deformation in individual passes) on the mechanical properties and the obtained bar structure. The feedstock, namely, AZ31 magnesium alloy round bars with a diameter of 30 mm, were rolled in RSR to the final diameter of 15 mm with different levels of deformation in successive passes, at a temperature of 400 °C. The bars obtained as a result of the RSR rolling process have different hardness on the cross-section as well as a characteristic gradient grain size distribution. Based on the conducted research, it can be concluded that the use of a larger number of passes with a smaller cross-section reduction will result in an improved formation of a bimodal structure consisting of a highly fragmented near-surface structure and in the half of the radius of the structure of fragmented grains at the boundaries of larger grains. Full article

(This article belongs to the Special Issue Radial-Shear and Screw Rolling Process)

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33 pages, 37468 KiB

Open AccessEditor’s ChoiceReview

Photocatalytic Reduction of Carbon Dioxide on TiO₂ Heterojunction Photocatalysts—A Review

by Beatriz Trindade Barrocas, Nela Ambrožová and Kamila Kočí

Materials 2022, 15(3), 967; https://doi.org/10.3390/ma15030967 - 26 Jan 2022

Cited by 45 | Viewed by 10092

Abstract

The photocatalytic reduction of carbon dioxide to renewable fuel or other valuable chemicals using solar energy is attracting the interest of researchers because of its great potential to offer a clean fuel alternative and solve global warming problems. Unfortunately, the efficiency of CO [...] Read more.

The photocatalytic reduction of carbon dioxide to renewable fuel or other valuable chemicals using solar energy is attracting the interest of researchers because of its great potential to offer a clean fuel alternative and solve global warming problems. Unfortunately, the efficiency of CO₂ photocatalytic reduction remains not very high due to the fast recombination of photogenerated electron–hole and small light utilization. Consequently, tremendous efforts have been made to solve these problems, and one possible solution is the use of heterojunction photocatalysts. This review begins with the fundamental aspects of CO₂ photocatalytic reduction and the fundamental principles of various heterojunction photocatalysts. In the following part, we discuss using TiO₂ heterojunction photocatalysts with other semiconductors, such as C₃N₄, CeO₂, CuO, CdS, MoS₂, GaP, CaTiO₃ and FeTiO₃. Finally, a concise summary and presentation of perspectives in the field of heterojunction photocatalysts are provided. The review covers references in the years 2011–2021. Full article

(This article belongs to the Special Issue Advanced Oxide-Based Materials for Photocatalytic Applications)

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14 pages, 3425 KiB

Open AccessEditor’s ChoiceArticle

Numerical Analysis of the Relationship between Friction Coefficient and Repose Angle of Blast Furnace Raw Materials by Discrete Element Method

by Shiyu Wei, Han Wei, Henrik Saxen and Yaowei Yu

Materials 2022, 15(3), 903; https://doi.org/10.3390/ma15030903 - 25 Jan 2022

Cited by 15 | Viewed by 4211

Abstract

In recent years, the discrete element method (DEM) has been widely used to study the factors affecting the repose angle and calibrate particle parameters for simulations. In this paper, DEM is used to study the effects of the coefficient of rolling and static [...] Read more.

In recent years, the discrete element method (DEM) has been widely used to study the factors affecting the repose angle and calibrate particle parameters for simulations. In this paper, DEM is used to study the effects of the coefficient of rolling and static friction of pellet, sinter and coke particles on the repose angle. By comparison of the results of simulations and physical experiments, the coefficients of rolling and static friction suitable for simulation work are determined. The results demonstrate that repose angle increases with the coefficient of rolling and static friction, but the rate of increase gradually decays, when the coefficient of rolling friction exceeds 0.4 or the coefficient of static friction exceeds 0.35. The coefficient of static friction has a greater impact on the repose angle than the coefficient of rolling friction. The rougher of the base surface, the larger the repose angle of the formed particle piled. It can be concluded that appropriate coefficient of rolling and static friction for simulations can be obtained by the outlined procedure. Full article

(This article belongs to the Special Issue Advances in Computational Materials Tribology)

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17 pages, 12742 KiB

Open AccessEditor’s ChoiceArticle

Optical Coherence Elastography as a Tool for Studying Deformations in Biomaterials: Spatially-Resolved Osmotic Strain Dynamics in Cartilaginous Samples

by Yulia Alexandrovskaya, Olga Baum, Alexander Sovetsky, Alexander Matveyev, Lev Matveev, Emil Sobol and Vladimir Zaitsev

Materials 2022, 15(3), 904; https://doi.org/10.3390/ma15030904 - 25 Jan 2022

Cited by 13 | Viewed by 3162

Abstract

This paper presents a recently developed variant of phase-resolved Optical Coherence Elastography (OCE) enabling non-contact visualization of transient local strains of various origins in biological tissues and other materials. In this work, we demonstrate the possibilities of this new technique for studying dynamics [...] Read more.

This paper presents a recently developed variant of phase-resolved Optical Coherence Elastography (OCE) enabling non-contact visualization of transient local strains of various origins in biological tissues and other materials. In this work, we demonstrate the possibilities of this new technique for studying dynamics of osmotically-induced strains in cartilaginous tissue impregnated with optical clearing agents (OCA). For poroelastic water-containing biological tissues, application of non-isotonic OCAs, various contrast additives, as well as drug solutions administration, may excite transient spatially-inhomogeneous strain fields of high magnitude in the tissue bulk, initiating mechanical and structural alterations. The range of the strain reliably observed by OCE varied from ±10⁻³ to ±0.4 for diluted and pure glycerol, correspondingly. The OCE-technique used made it possible to reveal previously inaccessible details of the complex spatio-temporal evolution of alternating-sign osmotic strains at the initial stages of agent diffusion. Qualitatively different effects produced by particular hydrophilic OCAs, such as glycerol and iohexol, are discussed, as well as concentration-dependent differences. Overall, the work demonstrates the unique abilities of the new OCE-modality in providing a deeper insight in real-time kinetics of osmotically-induced strains relevant to a broad range of biomedical applications. Full article

(This article belongs to the Special Issue Feature Paper in Optical and Photonic Materials)

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13 pages, 7006 KiB

Open AccessEditor’s ChoiceArticle

Effect of Delamination and Grain Refinement on Fracture Energy of Ultrafine-Grained Steel Determined Using an Instrumented Charpy Impact Test

by Tadanobu Inoue and Yuuji Kimura

Materials 2022, 15(3), 867; https://doi.org/10.3390/ma15030867 - 24 Jan 2022

Cited by 18 | Viewed by 3795

Abstract

Improving the balance of strength and toughness in structural materials is an ongoing challenge. Delamination and grain refinement are some of the methods used to do this. In this paper, two different steels, 0.15% C–0.3% Si–1.5% Mn–Fe and 0.4% C–2% Si–1% Cr–1% Mo–Fe [...] Read more.

Improving the balance of strength and toughness in structural materials is an ongoing challenge. Delamination and grain refinement are some of the methods used to do this. In this paper, two different steels, 0.15% C–0.3% Si–1.5% Mn–Fe and 0.4% C–2% Si–1% Cr–1% Mo–Fe (mass %), were prepared. Two steel bars with an ultrafine elongated grain (UFEG) structure were fabricated via multipass warm caliber rolling. The UFEG steels were characterized by a strong <110>//rolling-direction fiber texture. The transverse grain size, d_t, was 1.0 µm for the low-carbon steel and 0.26 µm for the medium-carbon steel. For comparison, conventional heat-treated steels were also fabricated. An instrumented Charpy impact test was performed, and the impact load (P) and deflection (u) during the test were recorded. The P–u relations at the test temperature at which delamination fracture occurred exhibited a unique curve. Delamination effectively enhances the low-temperature toughness, and this was characterized by a plateau region of constant load in the P–u curve. Assuming no delamination, two routes in the P–u curves, the ductile route and the brittle route, were proposed. The results showed that the proposed methods can be predicted by an energy curve for ultrafine grained steels. Delamination is a more effective method of enhancing toughness for ultra-high-strength steels. Full article

(This article belongs to the Special Issue Delamination and Fracture Problems in Modern Engineering Materials)

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22 pages, 5492 KiB

Open AccessEditor’s ChoiceArticle

Fragmentation of Beaded Fibres in a Composite

by Carol Winnifred Rodricks, Israel Greenfeld, Bodo Fiedler and Hanoch Daniel Wagner

Materials 2022, 15(3), 890; https://doi.org/10.3390/ma15030890 - 24 Jan 2022

Cited by 4 | Viewed by 3711

Abstract

The fibre–matrix interface plays an important role in the overall mechanical behaviour of a fibre-reinforced composite, but the classical approach to improving the interface through chemical sizing is bounded by the materials’ properties. By contrast, structural and/or geometrical modification of the interface may [...] Read more.

The fibre–matrix interface plays an important role in the overall mechanical behaviour of a fibre-reinforced composite, but the classical approach to improving the interface through chemical sizing is bounded by the materials’ properties. By contrast, structural and/or geometrical modification of the interface may provide mechanical interlocking and have wider possibilities and benefits. Here we investigate the introduction of polymer beads along the interface of a fibre and validate their contribution by a single fibre fragmentation test. Using glass fibres and the same epoxy system for both matrix and beads, an increase of 17.5% is observed in the interfacial shear strength of the beaded fibres compared to fibres with no polymer beads. This increase should lead to a similar improvement in the strength and toughness of a beaded fibre composite when short fibres are used. The beads were also seen to stabilise the fragmentation process of a fibre by reducing the scatter in fragment density at a given strain. A case could also be made for a critical beads number—4 beads in our experimental system—to describe interfacial shear strength, analogous to a critical length used in fibre composites. Full article

(This article belongs to the Special Issue Feature Collection in Advanced Composites Section)

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29 pages, 4052 KiB

Open AccessEditor’s ChoiceReview

Structural and Insulating Behaviour of High-Permittivity Binary Oxide Thin Films for Silicon Carbide and Gallium Nitride Electronic Devices

by Raffaella Lo Nigro, Patrick Fiorenza, Giuseppe Greco, Emanuela Schilirò and Fabrizio Roccaforte

Materials 2022, 15(3), 830; https://doi.org/10.3390/ma15030830 - 22 Jan 2022

Cited by 23 | Viewed by 6704

Abstract

High-κ dielectrics are insulating materials with higher permittivity than silicon dioxide. These materials have already found application in microelectronics, mainly as gate insulators or passivating layers for silicon (Si) technology. However, since the last decade, the post-Si era began with the pervasive introduction [...] Read more.

High-κ dielectrics are insulating materials with higher permittivity than silicon dioxide. These materials have already found application in microelectronics, mainly as gate insulators or passivating layers for silicon (Si) technology. However, since the last decade, the post-Si era began with the pervasive introduction of wide band gap (WBG) semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), which opened new perspectives for high-κ materials in these emerging technologies. In this context, aluminium and hafnium oxides (i.e., Al₂O₃, HfO₂) and some rare earth oxides (e.g., CeO₂, Gd₂O₃, Sc₂O₃) are promising high-κ binary oxides that can find application as gate dielectric layers in the next generation of high-power and high-frequency transistors based on SiC and GaN. This review paper gives a general overview of high-permittivity binary oxides thin films for post-Si electronic devices. In particular, focus is placed on high-κ binary oxides grown by atomic layer deposition on WBG semiconductors (silicon carbide and gallium nitride), as either amorphous or crystalline films. The impacts of deposition modes and pre- or postdeposition treatments are both discussed. Moreover, the dielectric behaviour of these films is also presented, and some examples of high-κ binary oxides applied to SiC and GaN transistors are reported. The potential advantages and the current limitations of these technologies are highlighted. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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22 pages, 5130 KiB

Open AccessEditor’s ChoiceArticle

Accurate Estimation of Yield Strength and Ultimate Tensile Strength through Instrumented Indentation Testing and Chemical Composition Testing

by Martin Scales, Joel Anderson, Jeffrey A. Kornuta, Nathan Switzner, Ramon Gonzalez and Peter Veloo

Materials 2022, 15(3), 832; https://doi.org/10.3390/ma15030832 - 22 Jan 2022

Cited by 24 | Viewed by 5589

Abstract

Federal rule changes governing natural gas pipelines have made non-destructive techniques, such as instrumented indentation testing (IIT), an attractive alternative to destructive tests for verifying properties of steel pipeline segments that lack traceable records. Ongoing work from Pacific Gas and Electric Company’s (PG&E) [...] Read more.

Federal rule changes governing natural gas pipelines have made non-destructive techniques, such as instrumented indentation testing (IIT), an attractive alternative to destructive tests for verifying properties of steel pipeline segments that lack traceable records. Ongoing work from Pacific Gas and Electric Company’s (PG&E) materials verification program indicates that IIT measurements may be enhanced by incorporating chemical composition data. This paper presents data from PG&E’s large-scale IIT program that demonstrates the predictive capabilities of IIT and chemical composition data, with particular emphasis given to differences between ultimate tensile strength (UTS) and yield strength (YS). For this study, over 80 segments of line pipe were evaluated through tensile testing, IIT, and compositional testing by optical emission spectroscopy (OES) and laboratory combustion. IIT measurements of UTS were, generally, in better agreement with destructive tensile data than YS and exhibited about half as much variability as YS measurements on the same sample. The root-mean squared error for IIT measurements of UTS and YS, respectively, were 27 MPa (3.9 ksi) and 43 MPa (6.2 ksi). Next, a machine learning model was trained to estimate YS and UTS by combining IIT with chemical composition data. The agreement between the model’s estimated UTS and tensile UTS values was only slightly better than the IIT-only measurements, with an RMSE of 21 MPa (3.1 ksi). However, the YS estimates showed much greater improvement with an improved RMSE of 27 MPa (3.9 ksi). The experimental, mechanical, and metallurgical factors that contributed to IIT’s ability to consistently determine destructive UTS, and the differences in its interaction with composition as compared to YS, are discussed herein. Full article

(This article belongs to the Special Issue Instrumented Indentation Test: An Aiding Tool for Materials Science and Industry)

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11 pages, 2894 KiB

Open AccessEditor’s ChoiceArticle

Improved Methane Production by Photocatalytic CO₂ Conversion over Ag/In₂O₃/TiO₂ Heterojunctions

by Patricia Reñones, Fernando Fresno, Freddy E. Oropeza and Víctor A. de la Peña O’Shea

Materials 2022, 15(3), 843; https://doi.org/10.3390/ma15030843 - 22 Jan 2022

Cited by 7 | Viewed by 3306

Abstract

In this work, the role of In₂O₃ in a heterojunction with TiO₂ is studied as a way of increasing the photocatalytic activity for gas-phase CO₂ reduction using water as the electron donor and UV irradiation. Depending on the [...] Read more.

In this work, the role of In₂O₃ in a heterojunction with TiO₂ is studied as a way of increasing the photocatalytic activity for gas-phase CO₂ reduction using water as the electron donor and UV irradiation. Depending on the nature of the employed In₂O₃, different behaviors appear. Thus, with the high crystallite sizes of commercial In₂O₃, the activity is improved with respect to TiO₂, with modest improvements in the selectivity to methane. On the other hand, when In₂O₃ obtained in the laboratory, with low crystallite size, is employed, there is a further change in selectivity toward CH₄, even if the total conversion is lower than that obtained with TiO₂. The selectivity improvement in the heterojunctions is attributed to an enhancement in the charge transfer and separation with the presence of In₂O₃, more pronounced when smaller particles are used as in the case of laboratory-made In₂O₃, as confirmed by time-resolved fluorescence measurements. Ternary systems formed by these heterojunctions with silver nanoparticles reflect a drastic change in selectivity toward methane, confirming the role of silver as an electron collector that favors the charge transfer to the reaction medium. Full article

(This article belongs to the Special Issue Feature Paper in Section Catalytic Materials)

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16 pages, 2238 KiB

Open AccessEditor’s ChoiceArticle

Structural, Electronic, and Physical Properties of a New Layered Cr-Based Oxyarsenide Sr₂Cr₂AsO₃

by Yi-Qiang Lin, Hao Jiang, Hua-Xun Li, Shi-Jie Song, Si-Qi Wu, Zhi Ren and Guang-Han Cao

Materials 2022, 15(3), 802; https://doi.org/10.3390/ma15030802 - 21 Jan 2022

Cited by 3 | Viewed by 2305

Abstract

We report synthesis, crystal structure, and physical properties of Sr

_{2}

Cr

_{2}

AsO

_{3}

. The new compound crystallizes in a Sr

_{2}

GaO

_{3}

CuS-type structure with two distinct Cr sites, Cr(1) in the perovskite-like block layers of “Sr

_{3}

Cr [...] Read more.

We report synthesis, crystal structure, and physical properties of Sr

_{2}

Cr

_{2}

AsO

_{3}

. The new compound crystallizes in a Sr

_{2}

GaO

_{3}

CuS-type structure with two distinct Cr sites, Cr(1) in the perovskite-like block layers of “Sr

_{3}

Cr

_{2}

O

_{6}

” and Cr(2) in the ThCr

_{2}

Si

_{2}

-type layers of “SrCr

_{2}

As

_{2}

”. An inter-block-layer charge transfer is explicitly evidenced, which dopes electrons in the CrO

_{2}

planes and simultaneously dopes holes into the CrAs layers. Measurements of electrical resistivity, magnetization, and specific heat, in combination with density-functional theoretical calculations, indicate that the title material is an antiferromagnetic metal. The Cr(2) magnetic moments in the CrAs layers order at 420 K, while the Cr(1) spins in the CrO

_{2}

planes show quasi-two-dimensional magnetism with long-range ordering below 80 K. Both Néel temperatures are significantly reduced, compared with those of the cousin material Sr

_{2}

Cr

_{3}

As

_{2}

O

_{2}

, probably due to the intrinsic charge-carrier doping. Complex re-entrant magnetic transitions with a huge magnetic hysteresis were observed at low temperatures. Full article

(This article belongs to the Special Issue Quantum Materials: Superconductivity and Topology)

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14 pages, 2209 KiB

Open AccessEditor’s ChoiceArticle

Long-Term Water Balance Evaluation in Glass Ionomer Restorative Materials

by Howard Roberts, David Berzins and John Nicholson

Materials 2022, 15(3), 807; https://doi.org/10.3390/ma15030807 - 21 Jan 2022

Cited by 7 | Viewed by 2325

Abstract

The complex role of water in glass ionomer cement (polyalkenoate) dental restorative materials has been studied, but much of the present understanding concerning water balance within these materials is based on very early studies and short-term experiments. This study evaluated the nature of [...] Read more.

The complex role of water in glass ionomer cement (polyalkenoate) dental restorative materials has been studied, but much of the present understanding concerning water balance within these materials is based on very early studies and short-term experiments. This study evaluated the nature of the water species of six conventional and four resin modified glass ionomer restorative materials over 3 years using thermogravimetric analysis techniques. Materials were prepared, placed in crucibles, and stored in physiologic phosphate buffered saline and evaluated at 24 h, 1 week, and then at 1, 3, 6, 9, 12, 18, 24, 30 and 36 months. All materials demonstrated a significant increase in unbound water percentage content but except for the resin modified materials, the enthalpy required to remove the unbound water species did not significantly change over 36 months. Also, bound water content percentage and removal enthalpy was established at 24 h, as no significant increase was noted in both bound water content and removal enthalpy over the course of this evaluation. This study suggests that unbound water species may increase with time and is loosely held except for the resin modified materials. Protective coatings placement and re-evaluation are prudent to prevent unbound water loss. Full article

(This article belongs to the Special Issue Mechanical Properties and Microstructures of Glass-Ionomer Cements)

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