Materials

24 pages, 6212 KiB

Open AccessEditor’s ChoiceReview

A Review of Trends in Corrosion-Resistant Structural Steels Research—From Theoretical Simulation to Data-Driven Directions

by Di Xu, Zibo Pei, Xiaojia Yang, Qing Li, Fan Zhang, Renzheng Zhu, Xuequn Cheng and Lingwei Ma

Materials 2023, 16(9), 3396; https://doi.org/10.3390/ma16093396 - 26 Apr 2023

Cited by 3 | Viewed by 2182

Abstract

This paper provides a review of models commonly used over the years in the study of microscopic models of material corrosion mechanisms, data mining methods and the corrosion-resistant performance control of structural steels. The virtual process of material corrosion is combined with experimental [...] Read more.

This paper provides a review of models commonly used over the years in the study of microscopic models of material corrosion mechanisms, data mining methods and the corrosion-resistant performance control of structural steels. The virtual process of material corrosion is combined with experimental data to reflect the microscopic mechanism of material corrosion from a nano-scale to macro-scale, respectively. Data mining methods focus on predicting and modeling the corrosion rate and corrosion life of materials. Data-driven control of the corrosion resistance of structural steels is achieved through micro-alloying and organization structure control technology. Corrosion modeling has been used to assess the effects of alloying elements, grain size and organization purity on corrosion resistance, and to determine the contents of alloying elements. Full article

(This article belongs to the Special Issue Commemorating the Launch of the Section 'Metals and Alloys')

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23 pages, 3855 KiB

Open AccessEditor’s ChoiceReview

Rheology of Recycled PET

by Ilaria Cusano, Laura Campagnolo, Marco Aurilia, Salvatore Costanzo and Nino Grizzuti

Materials 2023, 16(9), 3358; https://doi.org/10.3390/ma16093358 - 25 Apr 2023

Cited by 8 | Viewed by 2758

Abstract

Polyethylene terephthalate (PET) is a thermoplastic material that is widely used in many application fields, such as packaging, construction and household products. Due to the relevant contribution of PET to global yearly solid waste, the recycling of such material has become an important [...] Read more.

Polyethylene terephthalate (PET) is a thermoplastic material that is widely used in many application fields, such as packaging, construction and household products. Due to the relevant contribution of PET to global yearly solid waste, the recycling of such material has become an important issue. Disposed PET does not maintain the mechanical properties of virgin material, as exposure to water and other substances can cause multiple chain scissions, with subsequent degradation of the viscoelastic properties. For this reason, chain extension is needed to improve the final properties of the recycled product. Chain extension is generally performed through reactive extrusion. As the latter involves structural modification and flow of PET molecules, rheology is a relevant asset for understanding the process and tailoring the mechanical properties of the final products. This paper briefly reviews relevant rheological studies associated with the recycling of polyethylene terephthalate through the reactive extrusion process. Full article

(This article belongs to the Special Issue Advanced Polymeric Materials: Synthesis, Properties, and Applications)

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12 pages, 2948 KiB

Open AccessEditor’s ChoiceArticle

Evolution of the Growth Mode and Its Consequences during Bulk Crystallization of GaN

by Tomasz Sochacki, Robert Kucharski, Karolina Grabianska, Jan L. Weyher, Magdalena A. Zajac, Malgorzata Iwinska, Lutz Kirste and Michal Bockowski

Materials 2023, 16(9), 3360; https://doi.org/10.3390/ma16093360 - 25 Apr 2023

Cited by 1 | Viewed by 1064

Abstract

A detailed analysis of morphology of gallium nitride crystal growth obtained by ammonothermal and halide vapor phase epitaxy methods was carried out. The work was conducted to determine the source of triangular planar defects visible in X-ray topography as areas with locally different [...] Read more.

A detailed analysis of morphology of gallium nitride crystal growth obtained by ammonothermal and halide vapor phase epitaxy methods was carried out. The work was conducted to determine the source of triangular planar defects visible in X-ray topography as areas with locally different lattice parameters. It is shown that the occurrence of these defects is related to growth hillocks. Particular attention was paid to analyzing the manner and consequences of merging hillocks. In the course of the study, the nature of the mentioned defects and the cause of their formation were determined. It was established that the appearance of the defects depends on the angle formed between the steps located on the sides of two adjacent hillocks. A universal growth model is presented to explain the cause of heterogeneity during the merging of growth hillocks. Full article

(This article belongs to the Section Electronic Materials)

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8 pages, 2210 KiB

Open AccessEditor’s ChoiceCommunication

Boron-Related Defects in N-Type 4H-SiC Schottky Barrier Diodes

by Tihomir Knezevic, Eva Jelavić, Yuichi Yamazaki, Takeshi Ohshima, Takahiro Makino and Ivana Capan

Materials 2023, 16(9), 3347; https://doi.org/10.3390/ma16093347 - 25 Apr 2023

Cited by 1 | Viewed by 1352

Abstract

We report on boron-related defects in the low-doped n-type (nitrogen-doped) 4H-SiC semitransparent Schottky barrier diodes (SBDs) studied by minority carrier transient spectroscopy (MCTS). An unknown concentration of boron was introduced during chemical vapor deposition (CVD) crystal growth. Boron incorporation was found to lead [...] Read more.

We report on boron-related defects in the low-doped n-type (nitrogen-doped) 4H-SiC semitransparent Schottky barrier diodes (SBDs) studied by minority carrier transient spectroscopy (MCTS). An unknown concentration of boron was introduced during chemical vapor deposition (CVD) crystal growth. Boron incorporation was found to lead to the appearance of at least two boron-related deep-level defects, namely, shallow (B) and deep boron (D-center), with concentrations as high as 1 × 10¹⁵ cm⁻³. Even though the boron concentration exceeded the nitrogen doping concentration by almost an order of magnitude, the steady-state electrical characteristics of the n-type 4H-SiC SBDs did not deteriorate. Full article

(This article belongs to the Section Electronic Materials)

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30 pages, 3425 KiB

Open AccessEditor’s ChoiceReview

Synthesis Methods and Optical Sensing Applications of Plasmonic Metal Nanoparticles Made from Rhodium, Platinum, Gold, or Silver

by Elizaveta Demishkevich, Andrey Zyubin, Alexey Seteikin, Ilia Samusev, Inkyu Park, Chang Kwon Hwangbo, Eun Ha Choi and Geon Joon Lee

Materials 2023, 16(9), 3342; https://doi.org/10.3390/ma16093342 - 24 Apr 2023

Cited by 6 | Viewed by 2963

Abstract

The purpose of this paper is to provide an in-depth review of plasmonic metal nanoparticles made from rhodium, platinum, gold, or silver. We describe fundamental concepts, synthesis methods, and optical sensing applications of these nanoparticles. Plasmonic metal nanoparticles have received a lot of [...] Read more.

The purpose of this paper is to provide an in-depth review of plasmonic metal nanoparticles made from rhodium, platinum, gold, or silver. We describe fundamental concepts, synthesis methods, and optical sensing applications of these nanoparticles. Plasmonic metal nanoparticles have received a lot of interest due to various applications, such as optical sensors, single-molecule detection, single-cell detection, pathogen detection, environmental contaminant monitoring, cancer diagnostics, biomedicine, and food and health safety monitoring. They provide a promising platform for highly sensitive detection of various analytes. Due to strongly localized optical fields in the hot-spot region near metal nanoparticles, they have the potential for plasmon-enhanced optical sensing applications, including metal-enhanced fluorescence (MEF), surface-enhanced Raman scattering (SERS), and biomedical imaging. We explain the plasmonic enhancement through electromagnetic theory and confirm it with finite-difference time-domain numerical simulations. Moreover, we examine how the localized surface plasmon resonance effects of gold and silver nanoparticles have been utilized for the detection and biosensing of various analytes. Specifically, we discuss the syntheses and applications of rhodium and platinum nanoparticles for the UV plasmonics such as UV-MEF and UV-SERS. Finally, we provide an overview of chemical, physical, and green methods for synthesizing these nanoparticles. We hope that this paper will promote further interest in the optical sensing applications of plasmonic metal nanoparticles in the UV and visible ranges. Full article

(This article belongs to the Special Issue Advances in Metal-Based Nanoparticles)

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11 pages, 1439 KiB

Open AccessEditor’s ChoiceArticle

Dentinal Tubule Penetrability and Bond Strength of Two Novel Calcium Silicate-Based Root Canal Sealers

by Karissa Shieh, Jack Yang, Elsa Heng Zhu, Ove Andreas Peters and Sepanta Hosseinpour

Materials 2023, 16(9), 3309; https://doi.org/10.3390/ma16093309 - 23 Apr 2023

Cited by 2 | Viewed by 1398

Abstract

Background: Once the chemo-mechanical preparation of root canals is finished, achieving a complete seal of the root canal system becomes crucial in determining the long-term success of endodontic treatment. The important goals of root canal obturation are to minimize leakage and achieve an [...] Read more.

Background: Once the chemo-mechanical preparation of root canals is finished, achieving a complete seal of the root canal system becomes crucial in determining the long-term success of endodontic treatment. The important goals of root canal obturation are to minimize leakage and achieve an adequate seal. Thus, a material that possesses satisfactory mechanical characteristics, is biocompatible, and has the ability to penetrate the dentine tubules adequately is needed. Aim: This study aimed to compare the penetrability and bond strength between two calcium silicate-based sealers and an epoxy resin-based sealer, as well as examine the relationship between penetrability and bond strength for the different sealers. Method and materials: Thirty-nine recently extracted single-rooted human premolar teeth were instrumented and divided evenly into three groups (n = 13), according to the sealer used for obturation: AH Plus Jet, EndoSequence, and AH Plus Bioceramic Sealer. Three teeth (30 slices) were randomly selected out of each for analysis using confocal laser scanning microscopy to assess penetrability. The remaining ten teeth (90 slices) in each group were subject to push-out tests using a universal testing machine. All teeth were sectioned into nine transverse slices of 0.9 mm thickness for their respective tests (apical, middle, coronal). Results: AH Plus Jet exhibited significantly lower penetrability and significantly higher bond strength compared to EndoSequence BC sealer (p = 0.002) and AH Plus Bioceramic Sealer (p = 0.006). There was no significant difference between EndoSequence BC sealer and AH Plus Bioceramic Sealer in terms of either penetrability or bond strength. No correlation was found between penetrability and bond strength. Conclusions: Within the limitation of this study and regardless of the location in the canal, the bioceramic based root canal sealers appeared to perform better than the epoxy resin-based sealer in terms of dentinal penetration rate. Further studies are required to compare other biomechanical properties of bioceramic sealers including setting characteristics and bacterial leakage. Full article

(This article belongs to the Special Issue Novel Dental Materials: Recent Developments, Advances, and Applications)

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10 pages, 3360 KiB

Open AccessEditor’s ChoiceArticle

Ferroelectricity and Oxide Reliability of Stacked Hafnium–Zirconium Oxide Devices

by Ruo-Yin Liao, Hsuan-Han Chen, Ping-Yu Lin, Ting-An Liang, Kuan-Hung Su, I-Cheng Lin, Chen-Hao Wen, Wu-Ching Chou, Hsiao-Hsuan Hsu and Chun-Hu Cheng

Materials 2023, 16(9), 3306; https://doi.org/10.3390/ma16093306 - 23 Apr 2023

Viewed by 1711

Abstract

In this work, we investigate the ferroelectricity of stacked zirconium oxide and hafnium oxide (stacked HfZrO) with different thickness ratios under metal gate stress and simultaneously evaluate the electrical reliability of stacked ferroelectric films. Based on experimental results, we find that the stacked [...] Read more.

In this work, we investigate the ferroelectricity of stacked zirconium oxide and hafnium oxide (stacked HfZrO) with different thickness ratios under metal gate stress and simultaneously evaluate the electrical reliability of stacked ferroelectric films. Based on experimental results, we find that the stacked HfZrO films not only exhibited excellent ferroelectricity but also demonstrated a high performance on reliability. The optimized condition of the 45% Zr proportion exhibited a robust ferroelectric polarization value of 32.57 μC/cm², and a polarization current with a peak value of 159.98 μA. Besides this, the ferroelectric stacked HfZrO also demonstrated good reliability with a ten-year lifetime under >−2 V constant voltage stress. Therefore, the appropriate modulation of zirconium proportion in stacked HfZrO showed great promise for integrating in high-performance ferroelectric memory. Full article

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

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15 pages, 1813 KiB

Open AccessEditor’s ChoiceArticle

Cumulative Fatigue Damage of Composite Laminates: Engineering Rule and Life Prediction Aspect

by Nikolaos D. Batsoulas and Georgios I. Giannopoulos

Materials 2023, 16(8), 3271; https://doi.org/10.3390/ma16083271 - 21 Apr 2023

Cited by 2 | Viewed by 1361

Abstract

The analysis of cumulative fatigue damage is an important factor in predicting the life of composite elements and structures that are exposed to field load histories. A method for predicting the fatigue life of composite laminates under varying loads is suggested in this [...] Read more.

The analysis of cumulative fatigue damage is an important factor in predicting the life of composite elements and structures that are exposed to field load histories. A method for predicting the fatigue life of composite laminates under varying loads is suggested in this paper. A new theory of cumulative fatigue damage is introduced grounded on the Continuum Damage Mechanics approach that links the damage rate to cyclic loading through the damage function. A new damage function is examined with respect to hyperbolic isodamage curves and remaining life characteristics. The nonlinear damage accumulation rule that is presented in this study utilizes only one material property and overcomes the limitations of other rules while maintaining implementation simplicity. The benefits of the proposed model and its correlation with other relevant techniques are demonstrated, and a broad range of independent fatigue data from the literature is used for comparison to investigate its performance and validate its reliability. Full article

(This article belongs to the Special Issue Analysis and Design of Structures and Materials)

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14 pages, 3042 KiB

Open AccessEditor’s ChoiceArticle

Detecting Single Microwave Photons with NV Centers in Diamond

by Olivia Woodman, Abdolreza Pasharavesh, Christopher Wilson and Michal Bajcsy

Materials 2023, 16(8), 3274; https://doi.org/10.3390/ma16083274 - 21 Apr 2023

Viewed by 2186

Abstract

We propose a scheme for detecting single microwave photons using dipole-induced transparency (DIT) in an optical cavity resonantly coupled to a spin-selective transition of a negatively charged nitrogen-vacancy (NV⁻) defect in diamond crystal lattices. In this scheme, the microwave photons control [...] Read more.

We propose a scheme for detecting single microwave photons using dipole-induced transparency (DIT) in an optical cavity resonantly coupled to a spin-selective transition of a negatively charged nitrogen-vacancy (NV⁻) defect in diamond crystal lattices. In this scheme, the microwave photons control the interaction of the optical cavity with the NV⁻ center by addressing the spin state of the defect. The spin, in turn, is measured with high fidelity by counting the number of reflected photons when the cavity is probed by resonant laser light. To evaluate the performance of the proposed scheme, we derive the governing master equation and solve it through both direct integration and the Monte Carlo approach. Using these numerical simulations, we then investigate the effects of different parameters on the detection performance and find their corresponding optimized values. Our results indicate that detection efficiencies approaching 90% and fidelities exceeding 90% could be achieved when using realistic optical and microwave cavity parameters. Full article

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

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13 pages, 7514 KiB

Open AccessEditor’s ChoiceArticle

Influence of Calcination Temperature and Amount of Low-Grade Clay Replacement on Mitigation of the Alkali–Silica Reaction

by Daria Jóźwiak-Niedźwiedzka, Roman Jaskulski, Kinga Dziedzic, Aneta Antolik and Mariusz Dąbrowski

Materials 2023, 16(8), 3210; https://doi.org/10.3390/ma16083210 - 19 Apr 2023

Cited by 2 | Viewed by 1389

Abstract

Results of experimental investigation on the mitigation of alkali–silica reaction (ASR) by low-grade calcined clay are presented. Domestic clay with an Al₂O₃ content equal to 26% and SiO₂—58% was used. The calcination temperatures were as follows: 650 °C, [...] Read more.

Results of experimental investigation on the mitigation of alkali–silica reaction (ASR) by low-grade calcined clay are presented. Domestic clay with an Al₂O₃ content equal to 26% and SiO₂—58% was used. The calcination temperatures were as follows: 650 °C, 750 °C, 850 °C and 950 °C, which were chosen much more widely than presented in previous studies. Pozzolanity of the raw and calcined clay was determined with the Fratini test. The performance of calcined clay to mitigate ASR was evaluated according to ASTM C1567 using reactive aggregates. A control mortar mixture was prepared with 100% Portland cement (Na₂O_eq = 1.12%) as a binder with reactive aggregate, and test mixtures were made with 10% and 20% of calcined clay as a cement replacement. The microstructure of the specimens was observed on the polished sections using scanning electron microscope (SEM) operated in backscattered mode (BSE). The results of expansion of mortar bars with reactive aggregate showed that replacing cement with calcined clay reduced the expansion of the mortar bars. The greater the cement replacement, the better results in terms of ASR mitigation. However, the influence of the calcination temperature was not as clear. The opposite trend was found with the use of 10% or 20% calcined clay. Full article

(This article belongs to the Special Issue Building Materials Engineering and Innovative Sustainable Materials)

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11 pages, 1952 KiB

Open AccessEditor’s ChoiceArticle

Effect of the Chemical and Mechanical Recycling of PET on the Thermal and Mechanical Response of Mortars and Premixed Screeds

by Michela Lerna, Dora Foti, Andrea Petrella, Maria Francesca Sabbà and Sulyman Mansour

Materials 2023, 16(8), 3155; https://doi.org/10.3390/ma16083155 - 17 Apr 2023

Cited by 5 | Viewed by 1659

Abstract

In this paper, recycled polyethylene terephthalate (PET) was used to produce eco-innovative engineering materials with optimized performance, minimizing the environmental impact deriving from plastic consumption activity and limiting the continuous consumption of raw materials. The recycled PET obtained from waste bottles, commonly used [...] Read more.

In this paper, recycled polyethylene terephthalate (PET) was used to produce eco-innovative engineering materials with optimized performance, minimizing the environmental impact deriving from plastic consumption activity and limiting the continuous consumption of raw materials. The recycled PET obtained from waste bottles, commonly used to improve the ductility of concrete, has been used with a different weight percentage as plastic aggregate in the replacement of sand in cement mortars and as fibers added to premixed screeds. In detail, the effect of PET treatment (chemical or mechanical) on the thermal performance was evaluated. Non-destructive physical tests were conducted to determine the thermal conductivity of the investigated building materials. The performed tests showed that chemically depolymerized PET aggregate and recycled PET fibers derived from plastic wastes can reduce the heat conduction capacity of the cementitious materials with limited reduction in compressive strength. The results of the experimental campaign have made it possible to evaluate the influence of the recycled material on the physical and mechanical properties and its feasibility in non-structural applications. Full article

(This article belongs to the Special Issue Smart Non-destructive Testing and Inspection of Engineering Materials)

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14 pages, 20394 KiB

Open AccessEditor’s ChoiceArticle

A Parameterized Leblond–Devaux Equation for Predicting Phase Evolution during Welding E36 and E36Nb Marine Steels

by Jun Fu, G. M. A. M. El-Fallah, Qing Tao and Hongbiao Dong

Materials 2023, 16(8), 3150; https://doi.org/10.3390/ma16083150 - 17 Apr 2023

Cited by 1 | Viewed by 1271

Abstract

High heat input welding can improve welding efficiency, but the impact toughness of the heat-affected zone (HAZ) deteriorates significantly. Thermal evolution in HAZ during welding is the key factor affecting welded joints’ microstructures and mechanical properties. In this study, the Leblond–Devaux equation for [...] Read more.

High heat input welding can improve welding efficiency, but the impact toughness of the heat-affected zone (HAZ) deteriorates significantly. Thermal evolution in HAZ during welding is the key factor affecting welded joints’ microstructures and mechanical properties. In this study, the Leblond–Devaux equation for predicting phase evolution during the welding of marine steels was parameterized. In experiments, E36 and E36Nb samples were cooled down at different rates from 0.5 to 75 °C/s; the obtained thermal and phase evolution data were used to construct continuous cooling transformation diagrams, which were used to derive the temperature-dependent parameters in the Leblond–Devaux equation. The equation was then used to predict phase evolution during the welding of E36 and E36Nb; the quantitative experimental phase fractions of the coarse grain zone were compared with simulated results to verify the prediction results, which are in good agreement. When heat input is 100 kJ/cm, phases in the HAZ of E36Nb are primarily granular bainite, whereas for E36, the phases are mainly bainite with acicular ferrite. When heat input increases to 250 kJ/cm, ferrite and pearlite form in both steels. The predictions agree with experimental observations. Full article

(This article belongs to the Section Metals and Alloys)

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10 pages, 3635 KiB

Open AccessEditor’s ChoiceArticle

Increasing Electrical Resistivity of P-Type BiFeO₃ Ceramics by Hydrogen Peroxide-Assisted Hydrothermal Synthesis

by Cristian Casut, Raul Bucur, Daniel Ursu, Iosif Malaescu and Marinela Miclau

Materials 2023, 16(8), 3130; https://doi.org/10.3390/ma16083130 - 16 Apr 2023

Viewed by 1028

Abstract

Bismuth ferrite (BiFeO₃, BFO) is still widely investigated both because of the great diversity of its possible applications and from the perspective of intrinsic defect engineering in the perovskite structure. Defect control in BiFeO₃ semiconductors could provide a key technology [...] Read more.

Bismuth ferrite (BiFeO₃, BFO) is still widely investigated both because of the great diversity of its possible applications and from the perspective of intrinsic defect engineering in the perovskite structure. Defect control in BiFeO₃ semiconductors could provide a key technology for overcoming undesirable limitations, namely, a strong leakage current, which is attributed to the presence of oxygen vacancies (V_O) and Bi vacancies (V_Bi). Our study proposes a hydrothermal method for the reduction of the concentration of V_Bi during the ceramic synthesis of BiFeO₃.Using hydrogen peroxide (H₂O₂) as part of the medium, p-type BiFeO₃ ceramics characterized by their low conductivity were obtained. Hydrogen peroxide acted as the electron donor in the perovskite structure, controlling V_Bi in the BiFeO₃ semiconductor, which caused the dielectric constant and loss to decrease along with the electrical resistivity. The reduction of Bi vacancies highlighted by a FT-IR and Mott—Schottky analysis has an expected contribution to the dielectric characteristic. A decrease in the dielectric constant (with approximately 40%) and loss (3 times) and an increase of the electrical resistivity (by 3 times) was achieved by the hydrogen peroxide-assisted hydrothermal synthesized BFO ceramics, as compared with the hydrothermal synthesized BFOs. Full article

(This article belongs to the Special Issue Elaboration of New Materials Using Hydrothermal Methods)

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17 pages, 6678 KiB

Open AccessEditor’s ChoiceArticle

Systematic Investigation on Supported Gold Catalysts Prepared by Fluorine-Free Basic Etching Ti₃AlC₂ in Selective Oxidation of Aromatic Alcohols to Aldehydes

by Hangwei Jiang, Xiya Chen, Danlan Cui, Kun Lu, Xiao Kong and Xingguang Zhang

Materials 2023, 16(8), 3139; https://doi.org/10.3390/ma16083139 - 16 Apr 2023

Cited by 1 | Viewed by 1118

Abstract

Conventional methods to prepare supported metal catalysts are chemical reduction and wet impregnation. This study developed and systematically investigated a novel reduction method based on simultaneous Ti₃AlC₂ fluorine-free etching and metal deposition to prepare gold catalysts. The new series of [...] Read more.

Conventional methods to prepare supported metal catalysts are chemical reduction and wet impregnation. This study developed and systematically investigated a novel reduction method based on simultaneous Ti₃AlC₂ fluorine-free etching and metal deposition to prepare gold catalysts. The new series of Au_pre/Ti₃Al_xC₂Ty catalysts were characterized by XRD, XPS, TEM, and SEM and were tested in the selective oxidation of representative aromatic alcohols to aldehydes. The catalytic results demonstrate the effectiveness of the preparation method and better catalytic performances of Au_pre/Ti₃Al_xC₂T_y, compared with those of catalysts prepared by traditional methods. Moreover, this work presents a comprehensive study on the influence of calcination in air, H₂, and Ar, and we found that the catalyst of Au_pre/Ti₃Al_xC₂T_y-Air600 obtained by calcination in air at 600 °C performed the best, owing to the synergistic effect between tiny surface TiO₂ species and Au NPs. The tests of reusability and hot filtration confirmed the catalyst stability. Full article

(This article belongs to the Special Issue Synthesis and Application of Catalytic Materials)

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34 pages, 2112 KiB

Open AccessEditor’s ChoiceReview

Nanotechnology Applied to Cellulosic Materials

by Ana Fernandes, Luísa Cruz-Lopes, Bruno Esteves and Dmitry Evtuguin

Materials 2023, 16(8), 3104; https://doi.org/10.3390/ma16083104 - 14 Apr 2023

Cited by 7 | Viewed by 4653

Abstract

In recent years, nanocellulosic materials have attracted special attention because of their performance in different advanced applications, biodegradability, availability, and biocompatibility. Nanocellulosic materials can assume three distinct morphologies, including cellulose nanocrystals (CNC), cellulose nanofibers (CNF), and bacterial cellulose (BC). This review consists of [...] Read more.

In recent years, nanocellulosic materials have attracted special attention because of their performance in different advanced applications, biodegradability, availability, and biocompatibility. Nanocellulosic materials can assume three distinct morphologies, including cellulose nanocrystals (CNC), cellulose nanofibers (CNF), and bacterial cellulose (BC). This review consists of two main parts related to obtaining and applying nanocelluloses in advanced materials. In the first part, the mechanical, chemical, and enzymatic treatments necessary for the production of nanocelluloses are discussed. Among chemical pretreatments, the most common approaches are described, such as acid- and alkali-catalyzed organosolvation, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, ammonium persulfate (APS) and sodium persulfate (SPS) oxidative treatments, ozone, extraction with ionic liquids, and acid hydrolysis. As for mechanical/physical treatments, methods reviewed include refining, high-pressure homogenization, microfluidization, grinding, cryogenic crushing, steam blasting, ultrasound, extrusion, aqueous counter collision, and electrospinning. The application of nanocellulose focused, in particular, on triboelectric nanogenerators (TENGs) with CNC, CNF, and BC. With the development of TENGs, an unparalleled revolution is expected; there will be self-powered sensors, wearable and implantable electronic components, and a series of other innovative applications. In the future new era of TENGs, nanocellulose will certainly be a promising material in their constitution. Full article

(This article belongs to the Special Issue Application of Natural Polymers in Bio-Based Products)

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15 pages, 6337 KiB

Open AccessEditor’s ChoiceArticle

Design and 3D Printing of Stretchable Conductor with High Dynamic Stability

by Chao Liu, Yuwei Wang, Shengding Wang, Xiangling Xia, Huiyun Xiao, Jinyun Liu, Siqi Hu, Xiaohui Yi, Yiwei Liu, Yuanzhao Wu, Jie Shang and Run-Wei Li

Materials 2023, 16(8), 3098; https://doi.org/10.3390/ma16083098 - 14 Apr 2023

Cited by 1 | Viewed by 1320

Abstract

As an indispensable part of wearable devices and mechanical arms, stretchable conductors have received extensive attention in recent years. The design of a high-dynamic-stability, stretchable conductor is the key technology to ensure the normal transmission of electrical signals and electrical energy of wearable [...] Read more.

As an indispensable part of wearable devices and mechanical arms, stretchable conductors have received extensive attention in recent years. The design of a high-dynamic-stability, stretchable conductor is the key technology to ensure the normal transmission of electrical signals and electrical energy of wearable devices under large mechanical deformation, which has always been an important research topic domestically and abroad. In this paper, a stretchable conductor with a linear bunch structure is designed and prepared by combining numerical modeling and simulation with 3D printing technology. The stretchable conductor consists of a 3D-printed bunch-structured equiwall elastic insulating resin tube and internally filled free-deformable liquid metal. This conductor has a very high conductivity exceeding 10⁴ S cm⁻¹, good stretchability with an elongation at break exceeding 50%, and great tensile stability, with a relative change in resistance of only about 1% at 50% tensile strain. Finally, this paper demonstrates it as a headphone cable (transmitting electrical signals) and a mobile phone charging wire (transmitting electrical energy), which proves its good mechanical and electrical properties and shows good application potential. Full article

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

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11 pages, 6187 KiB

Open AccessEditor’s ChoiceArticle

Optimization of PVDF-TrFE Based Electro-Conductive Nanofibers: Morphology and In Vitro Response

by William Serrano-Garcia, Iriczalli Cruz-Maya, Anamaris Melendez-Zambrana, Idalia Ramos-Colon, Nicholas J. Pinto, Sylvia W. Thomas and Vincenzo Guarino

Materials 2023, 16(8), 3106; https://doi.org/10.3390/ma16083106 - 14 Apr 2023

Cited by 1 | Viewed by 1290

Abstract

In this study, morphology and in vitro response of electroconductive composite nanofibers were explored for biomedical use. The composite nanofibers were prepared by blending the piezoelectric polymer poly(vinylidene fluoride–trifluorethylene) (PVDF-TrFE) and electroconductive materials with different physical and chemical properties such as copper oxide [...] Read more.

In this study, morphology and in vitro response of electroconductive composite nanofibers were explored for biomedical use. The composite nanofibers were prepared by blending the piezoelectric polymer poly(vinylidene fluoride–trifluorethylene) (PVDF-TrFE) and electroconductive materials with different physical and chemical properties such as copper oxide (CuO), poly(3-hexylthiophene) (P3HT), copper phthalocyanine (CuPc), and methylene blue (MB) resulting in unique combinations of electrical conductivity, biocompatibility, and other desirable properties. Morphological investigation via SEM analysis has remarked some differences in fiber size as a function of the electroconductive phase used, with a reduction of fiber diameters for the composite fibers of 12.43% for CuO, 32.87% for CuPc, 36.46% for P3HT, and 63% for MB. This effect is related to the peculiar electroconductive behavior of fibers: measurements of electrical properties showed the highest ability to transport charges of methylene blue, in accordance with the lowest fibers diameters, while P3HT poorly conducts in air but improves charge transfer during the fiber formation. In vitro assays showed a tunable response of fibers in terms of viability, underlining a preferential interaction of fibroblast cells to P3HT-loaded fibers that can be considered the most suitable for use in biomedical applications. These results provide valuable information for future studies to be addressed at optimizing the properties of composite nanofibers for potential applications in bioengineering and bioelectronics. Full article

(This article belongs to the Special Issue Piezoelectric Nanofibers: Recent Development, Challenges, and Applications)

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42 pages, 21104 KiB

Open AccessEditor’s ChoiceReview

Principles and Applications of Resonance Energy Transfer Involving Noble Metallic Nanoparticles

by Zhicong He, Fang Li, Pei Zuo and Hong Tian

Materials 2023, 16(8), 3083; https://doi.org/10.3390/ma16083083 - 13 Apr 2023

Cited by 4 | Viewed by 1897

Abstract

Over the past several years, resonance energy transfer involving noble metallic nanoparticles has received considerable attention. The aim of this review is to cover advances in resonance energy transfer, widely exploited in biological structures and dynamics. Due to the presence of surface plasmons, [...] Read more.

Over the past several years, resonance energy transfer involving noble metallic nanoparticles has received considerable attention. The aim of this review is to cover advances in resonance energy transfer, widely exploited in biological structures and dynamics. Due to the presence of surface plasmons, strong surface plasmon resonance absorption and local electric field enhancement are generated near noble metallic nanoparticles, and the resulting energy transfer shows potential applications in microlasers, quantum information storage devices and micro-/nanoprocessing. In this review, we present the basic principle of the characteristics of noble metallic nanoparticles, as well as the representative progress in resonance energy transfer involving noble metallic nanoparticles, such as fluorescence resonance energy transfer, nanometal surface energy transfer, plasmon-induced resonance energy transfer, metal-enhanced fluorescence, surface-enhanced Raman scattering and cascade energy transfer. We end this review with an outlook on the development and applications of the transfer process. This will offer theoretical guidance for further optical methods in distance distribution analysis and microscopic detection. Full article

(This article belongs to the Special Issue Fundamentals and Applications of Laser Micro/Nanostructuring and Synthesis of Micro/Nanomaterials)

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9 pages, 2520 KiB

Open AccessEditor’s ChoiceArticle

Band Gaps and Optical Properties of RENiO₃ upon Strain: Combining First-Principles Calculations and Machine Learning

by Xuchang Tang, Zhaokai Luo and Yuanyuan Cui

Materials 2023, 16(8), 3070; https://doi.org/10.3390/ma16083070 - 13 Apr 2023

Viewed by 1354

Abstract

Rare earth nickel-based perovskite oxides (RENiO₃) have been widely studied over recent decades because of their unique properties. In the synthesis of RENiO₃ thin films, a lattice mismatch frequently exists between the substrates and the thin films, [...] Read more.

Rare earth nickel-based perovskite oxides (RENiO₃) have been widely studied over recent decades because of their unique properties. In the synthesis of RENiO₃ thin films, a lattice mismatch frequently exists between the substrates and the thin films, which may affect the optical properties of RENiO₃. In this paper, the first-principles calculations were employed to study the electronic and optical properties of RENiO₃ under strain. The results showed that with the increase in tensile strength, the band gap generally shows a widening trend. For optical properties, the absorption coefficients increase with the enhancement of photon energies in the far-infrared range. The compressive strain increases the light absorption, while the tensile strain suppresses it. For the reflectivity spectrum in the far-infrared range, a minimum reflectivity displays around the photon energy of 0.3 eV. The tensile strain enhances the reflectivity in the range of 0.05–0.3 eV, whereas it decreases it when the photon energies are larger than 0.3 eV. Furthermore, machine learning algorithms were applied and found that the planar epitaxial strain, electronegativity, volume of supercells, and rare earth element ion radius play key roles in the band gaps. Photon energy, electronegativity, band gap, the ionic radius of the rare earth element, and the tolerance factor are key parameters significantly influencing the optical properties. Full article

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

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18 pages, 7297 KiB

Open AccessEditor’s ChoiceArticle

Molecular Understanding of the Interfacial Interaction and Corrosion Resistance between Epoxy Adhesive and Metallic Oxides on Galvanized Steel

by Shuangshuang Li, Yanliang Zhao, Hailang Wan, Jianping Lin and Junying Min

Materials 2023, 16(8), 3061; https://doi.org/10.3390/ma16083061 - 13 Apr 2023

Cited by 2 | Viewed by 1511

Abstract

The epoxy adhesive-galvanized steel adhesive structure has been widely used in various industrial fields, but achieving high bonding strength and corrosion resistance is a challenge. This study examined the impact of surface oxides on the interfacial bonding performance of two types of galvanized [...] Read more.

The epoxy adhesive-galvanized steel adhesive structure has been widely used in various industrial fields, but achieving high bonding strength and corrosion resistance is a challenge. This study examined the impact of surface oxides on the interfacial bonding performance of two types of galvanized steel with Zn–Al or Zn–Al–Mg coatings. Scanning electron microscopy and X-ray photoelectron spectroscopy analysis showed that the Zn–Al coating was covered by ZnO and Al₂O₃, while MgO was additionally found on the Zn–Al–Mg coating. Both coatings exhibited excellent adhesion in dry environments, but after 21 days of water soaking, the Zn–Al–Mg joint demonstrated better corrosion resistance than the Zn–Al joint. Numerical simulations revealed that metallic oxides of ZnO, Al₂O₃, and MgO had different adsorption preferences for the main components of the adhesive. The adhesion stress at the coating–adhesive interface was mainly due to hydrogen bonds and ionic interactions, and the theoretical adhesion stress of MgO adhesive system was higher than that of ZnO and Al₂O₃. The corrosion resistance of the Zn–Al–Mg adhesive interface was mainly due to the stronger corrosion resistance of the coating itself, and the lower water-related hydrogen bond content at the MgO adhesive interface. Understanding these bonding mechanisms can lead to the development of improved adhesive-galvanized steel structures with enhanced corrosion resistance. Full article

(This article belongs to the Special Issue Surface Engineering & Coating Technologies for Corrosion and Tribocorrosion Resistance)

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13 pages, 8894 KiB

Open AccessEditor’s ChoiceArticle

Biocomposite Foams with Multimodal Cellular Structures Based on Cork Granulates and Microwave Processed Egg White Proteins

by Giorgio Luciano, Adriano Vignali, Maurizio Vignolo, Roberto Utzeri, Fabio Bertini and Salvatore Iannace

Materials 2023, 16(8), 3063; https://doi.org/10.3390/ma16083063 - 13 Apr 2023

Cited by 2 | Viewed by 1347

Abstract

In an effort to reduce greenhouse gas emission, reduce the consumption of natural resources, and increase the sustainability of biocomposite foams, the present study focuses on the recycling of cork processing waste for the production of lightweight, non-structural, fireproof thermal and acoustic insulating [...] Read more.

In an effort to reduce greenhouse gas emission, reduce the consumption of natural resources, and increase the sustainability of biocomposite foams, the present study focuses on the recycling of cork processing waste for the production of lightweight, non-structural, fireproof thermal and acoustic insulating panels. Egg white proteins (EWP) were used as a matrix model to introduce an open cell structure via a simple and energy-efficient microwave foaming process. Samples with different compositions (ratio of EWP and cork) and additives (eggshells and inorganic intumescent fillers) were prepared with the aim of correlating composition, cellular structures, flame resistance, and mechanical properties. Full article

(This article belongs to the Special Issue Polymer Foams: Materials, Processing and Properties)

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10 pages, 4494 KiB

Open AccessEditor’s ChoiceArticle

Adsorption Tuning of Polarity and Magnetism in AgCr₂S₄ Monolayer

by Ranran Li, Yu Wang, Ning Ding, Shuai Dong and Ming An

Materials 2023, 16(8), 3058; https://doi.org/10.3390/ma16083058 - 12 Apr 2023

Cited by 2 | Viewed by 1430

Abstract

As a recent successfully exfoliated non-van der Waals layered material, AgCrS₂ has received a lot of attention. Motivated by its structure-related magnetic and ferroelectric behavior, a theoretical study on its exfoliated monolayer AgCr₂S₄ has been carried out in the [...] Read more.

As a recent successfully exfoliated non-van der Waals layered material, AgCrS₂ has received a lot of attention. Motivated by its structure-related magnetic and ferroelectric behavior, a theoretical study on its exfoliated monolayer AgCr₂S₄ has been carried out in the present work. Based on density functional theory, the ground state and magnetic order of monolayer AgCr₂S₄ have been determined. The centrosymmetry emerges upon two-dimensional confinement and thus eliminates the bulk polarity. Moreover, two-dimensional ferromagnetism appears in the CrS₂ layer of AgCr₂S₄ and can persist up to room temperature. The surface adsorption has also been taken into consideration, which shows a nonmonotonic effect on the ionic conductivity through ion displacement of the interlayer Ag, but has little impact on the layered magnetic structure. Full article

(This article belongs to the Special Issue First-Principles Calculations of 2D Magnetic Materials)

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10 pages, 3363 KiB

Open AccessEditor’s ChoiceArticle

The Role of GaN in the Heterostructure WS₂/GaN for SERS Applications

by Tsung-Shine Ko, En-Ting Lin, Yen-Teng Ho and Chen-An Deng

Materials 2023, 16(8), 3054; https://doi.org/10.3390/ma16083054 - 12 Apr 2023

Cited by 1 | Viewed by 1327

Abstract

In the application of WS₂ as a surface–enhanced Raman scattering (SERS) substrate, enhancing the charge transfer (CT) opportunity between WS₂ and analyte is an important issue for SERS efficiency. In this study, we deposited few-layer WS₂ (2–3 layers) on GaN [...] Read more.

In the application of WS₂ as a surface–enhanced Raman scattering (SERS) substrate, enhancing the charge transfer (CT) opportunity between WS₂ and analyte is an important issue for SERS efficiency. In this study, we deposited few-layer WS₂ (2–3 layers) on GaN and sapphire substrates with different bandgap characteristics to form heterojunctions using a chemical vapor deposition. Compared with sapphire, we found that using GaN as a substrate for WS₂ can effectively enhance the SERS signal, with an enhancement factor of 6.45 × 10⁴ and a limit of detection of 5 × 10⁻⁶ M for probe molecule Rhodamine 6G according to SERS measurement. Analysis of Raman, Raman mapping, atomic force microscopy, and SERS mechanism revealed that The SERS efficiency increased despite the lower quality of the WS₂ films on GaN compared to those on sapphire, as a result of the increased number of transition pathways present in the interface between WS₂ and GaN. These carrier transition pathways could increase the opportunity for CT, thus enhancing the SERS signal. The WS₂/GaN heterostructure proposed in this study can serve as a reference for enhancing SERS efficiency. Full article

(This article belongs to the Special Issue New Vibrational Spectroscopy Developments of Material Characterization)

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16 pages, 5264 KiB

Open AccessEditor’s ChoiceArticle

Lead Zirconate Titanate Transducers Embedded in Composite Laminates: The Influence of the Integration Method on Ultrasound Transduction

by Nina Kergosien, Ludovic Gavérina, Guillemette Ribay, Florence Saffar, Pierre Beauchêne, Olivier Mesnil and Olivier Bareille

Materials 2023, 16(8), 3057; https://doi.org/10.3390/ma16083057 - 12 Apr 2023

Cited by 3 | Viewed by 1353

Abstract

In the context of an embedded structural health monitoring (SHM) system, two methods of transducer integration into the core of a laminate carbon fiber-reinforced polymer (CFRP) are tested: cut-out and between two plies. This study focuses on the effect of integration methods on [...] Read more.

In the context of an embedded structural health monitoring (SHM) system, two methods of transducer integration into the core of a laminate carbon fiber-reinforced polymer (CFRP) are tested: cut-out and between two plies. This study focuses on the effect of integration methods on Lamb wave generation. For this purpose, plates with an embedded lead zirconate titanate (PZT) transducer are cured in an autoclave. The embedded PZT insulation, integrity, and ability to generate Lamb waves are checked with electromechanical impedance, X-rays, and laser Doppler vibrometry (LDV) measurements. Lamb wave dispersion curves are computed by LDV using two-dimensional fast Fourier transform (Bi-FFT) to study the quasi-antisymmetric mode (qA0) excitability in generation with the embedded PZT in the frequency range of 30 to 200 kHz. The embedded PZT is able to generate Lamb waves, which validate the integration procedure. The first minimum frequency of the embedded PZT shifts to lower frequencies and its amplitude is reduced compared to a surface-mounted PZT. Full article

(This article belongs to the Special Issue Organic Matrix Composites and Multifunctional Materials)

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13 pages, 6704 KiB

Open AccessEditor’s ChoiceArticle

Formation of Self-Healing Organic Coatings for Corrosion Protection of Al Alloys by Dispersion of Spherical and Fibrous Capsules

by Makoto Chiba, Yuki Tsuji, Rin Takada, Yuri Eguchi and Hideaki Takahashi

Materials 2023, 16(8), 3018; https://doi.org/10.3390/ma16083018 - 11 Apr 2023

Cited by 3 | Viewed by 4135

Abstract

In previous works, we developed a self-healing organic coating with dispersed spherical capsules for corrosion protection. The capsule consisted of a polyurethane shell and healing agent as the inner. When the coating was damaged physically, the capsules were broken, and the healing agent [...] Read more.

In previous works, we developed a self-healing organic coating with dispersed spherical capsules for corrosion protection. The capsule consisted of a polyurethane shell and healing agent as the inner. When the coating was damaged physically, the capsules were broken, and the healing agent was released from the broken capsules to the damaged area. The healing agent could react with moisture in the air to form the self-healing structure and cover the damaged area of coating. In the present investigation, a self-healing organic coating with spherical and fibrous capsules was formed on aluminum alloys. The corrosion behavior of the specimen coated with the self-healing coating was examined in a Cu²⁺/Cl⁻ solution after physical damage, and it was found that no corrosion occurred during the corrosion test. This is discussed in terms of the high healing ability of fibrous capsules as a result of the high projected area. Full article

(This article belongs to the Special Issue Science and Technology of Advanced Materials Applied to Society: Including Collections from the Latest Papers of KRIS 2023)

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28 pages, 15194 KiB

Open AccessEditor’s ChoiceArticle

Potential Utilization of Ground Eggshells as a Biofiller for Natural Rubber Biocomposites

by Anna Sowińska-Baranowska and Magdalena Maciejewska

Materials 2023, 16(8), 2988; https://doi.org/10.3390/ma16082988 - 9 Apr 2023

Viewed by 1991

Abstract

The aim of this work was application of ground eggshells in various amounts by weight as a biofiller for natural rubber (NR) biocomposites. Cetyltrimethylammonium bromide (CTAB), ionic liquids (ILs), i.e., 1-butyl-3-methylimidazolium chloride (BmiCl) and 1-decyl-3-methylimidazolium bromide (DmiBr), and silanes, i.e., (3-aminopropyl)-triethoxysilane (APTES) and [...] Read more.

The aim of this work was application of ground eggshells in various amounts by weight as a biofiller for natural rubber (NR) biocomposites. Cetyltrimethylammonium bromide (CTAB), ionic liquids (ILs), i.e., 1-butyl-3-methylimidazolium chloride (BmiCl) and 1-decyl-3-methylimidazolium bromide (DmiBr), and silanes, i.e., (3-aminopropyl)-triethoxysilane (APTES) and bis [3-(triethoxysilyl)propyl] tetrasulfide (TESPTS), were used to increase the activity of ground eggshells in the elastomer matrix and to ameliorate the cure characteristics and properties of NR biocomposites. The influence of ground eggshells, CTAB, ILs, and silanes on the crosslink density, mechanical properties, and thermal stability of NR vulcanizates and their resistance to prolonged thermo-oxidation were explored. The amount of eggshells affected the curing characteristics and crosslink density of the rubber composites and therefore their tensile properties. Vulcanizates filled with eggshells demonstrated higher crosslink density than the unfilled sample by approximately 30%, whereas CTAB and ILs increased the crosslink density by 40–60% compared to the benchmark. Owing to the enhanced crosslink density and uniform dispersion of ground eggshells, vulcanizates containing CTAB and ILs exhibited tensile strength improved by approximately 20% compared to those without these additives. Moreover, the hardness of these vulcanizates was increased by 35–42%. Application of both the biofiller and the tested additives did not significantly affect the thermal stability of cured NR compared to the unfilled benchmark. Most importantly, the eggshell-filled vulcanizates showed improved resistance to thermo-oxidative aging compared to the unfilled NR. Full article

(This article belongs to the Special Issue Advanced Rubber Composites II)

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21 pages, 2579 KiB

Open AccessEditor’s ChoiceReview

Thermal Conductivity of Aluminum Alloys—A Review

by Ailing Zhang and Yanxiang Li

Materials 2023, 16(8), 2972; https://doi.org/10.3390/ma16082972 - 8 Apr 2023

Cited by 18 | Viewed by 6543

Abstract

Aluminum alloys have been extensively used as heatproof and heat-dissipation components in automotive and communication industries, and the demand for aluminum alloys with higher thermal conductivity is increasing. Therefore, this review focuses on the thermal conductivity of aluminum alloys. First, we formulate the [...] Read more.

Aluminum alloys have been extensively used as heatproof and heat-dissipation components in automotive and communication industries, and the demand for aluminum alloys with higher thermal conductivity is increasing. Therefore, this review focuses on the thermal conductivity of aluminum alloys. First, we formulate the theory of thermal conduction of metals and effective medium theory, and then analyze the effect of alloying elements, secondary phases, and temperature on the thermal conductivity of aluminum alloys. Alloying elements are the most crucial factor, whose species, existing states, and mutual interactions significantly affect the thermal conductivity of aluminum. Alloying elements in a solid solution weaken the thermal conductivity of aluminum more dramatically than those in the precipitated state. The characteristics and morphology of secondary phases also affect thermal conductivity. Temperature also affects thermal conductivity by influencing the thermal conduction of electrons and phonons in aluminum alloys. Furthermore, recent studies on the effects of casting, heat treatment, and AM processes on the thermal conductivity of aluminum alloys are summarized, in which processes mainly affect thermal conductivity by varying existing states of alloying elements and the morphology of secondary phases. These analyses and summaries will further promote the industrial design and development of aluminum alloys with high thermal conductivity. Full article

(This article belongs to the Special Issue Structure and Mechanical Properties of Alloys, Volume II)

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16 pages, 48635 KiB

Open AccessEditor’s ChoiceArticle

On the Springback and Load in Three-Point Air Bending of the AW-2024 Aluminium Alloy Sheet with AW-1050A Aluminium Cladding

by Stanisław Kut, Grzegorz Pasowicz and Feliks Stachowicz

Materials 2023, 16(8), 2945; https://doi.org/10.3390/ma16082945 - 7 Apr 2023

Cited by 4 | Viewed by 1458

Abstract

This article presents the results of an analysis of the bending load characteristics and the springback phenomenon occurring during three-point bending of 1.0 and 2.0 mm thick AW-2024 aluminium alloy sheets with rolled AW-1050A cladding. A new proprietary equation was proposed for determining [...] Read more.

This article presents the results of an analysis of the bending load characteristics and the springback phenomenon occurring during three-point bending of 1.0 and 2.0 mm thick AW-2024 aluminium alloy sheets with rolled AW-1050A cladding. A new proprietary equation was proposed for determining the bending angle as a function of deflection, which takes into account the influence of the tool radius and the sheet thickness. The experimentally determined springback and bending load characteristics were compared with the results of numerical modelling using different models: Model I, a 2D model for a plane deformation state, disregarding the material properties of the clad layers; Model II, a 2D model for a plane deformation state, taking into account the material properties of the cladding layers; Model III, a 3D shell model with the Huber–von Mises isotropic plasticity condition; Model IV, a 3D shell model with the Hill anisotropic plasticity condition; and Model V, a 3D shell model with the Barlat anisotropic plasticity condition. The effectiveness of these five tested FEM models in predicting the bending load and springback characteristics was demonstrated. Model II was the most effective in predicting bending load, while Model III was the most effective in predicting the amount of springback after bending. Full article

(This article belongs to the Special Issue Technologies for Joining and Forming Thin-Walled Structures in the Construction of Transportation Vehicles)

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15 pages, 3810 KiB

Open AccessEditor’s ChoiceArticle

Probabilistic Modelling of Fracture Toughness of Composites with Discontinuous Reinforcement

by Grzegorz Mieczkowski, Tadeusz Szymczak, Dariusz Szpica and Andrzej Borawski

Materials 2023, 16(8), 2962; https://doi.org/10.3390/ma16082962 - 7 Apr 2023

Viewed by 1269

Abstract

The results presented in the paper are related to the prediction of the effective fracture toughness of particulate composites (K_ICeff). K_ICeff was determined using a probabilistic model supported by a cumulative probability function qualitatively following the Weibull [...] Read more.

The results presented in the paper are related to the prediction of the effective fracture toughness of particulate composites (K_ICeff). K_ICeff was determined using a probabilistic model supported by a cumulative probability function qualitatively following the Weibull distribution. Using this approach, it was possible to model two-phase composites with an arbitrarily defined volume fraction of each phase. The predicted value of the effective fracture toughness of the composite was determined based on the mechanical parameter of the reinforcement (fracture toughness), matrix (fracture toughness, Young’s modulus, yield stress), and composite (Young’s modulus, yield stress). The proposed method was validated: the determined fracture toughness of the selected composites was in accordance with the experimental data (the authors’ tests and literature data). In addition, the obtained results were compared with data captured by means of the rule of mixtures (ROM). It was found that the prediction of K_ICeff using the ROM was subject to a significant error. Moreover, a study of the effect of averaging the elastic–plastic parameters of the composite, on K_ICeff, was performed. The results showed that if the yield stress of the composite increased, a decrease in its fracture toughness was noticed, which is in line with the literature reports. Furthermore, it was noted that an increase in the Young’s modulus of the composite affected K_ICeff in the same way as a change in its yield stress. Full article

(This article belongs to the Special Issue Methodology of the Design and Testing of Composite Structures)

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20 pages, 9572 KiB

Open AccessEditor’s ChoiceArticle

Corrosion Behavior of Nitrided Layer of Ti6Al4V Titanium Alloy by Hollow Cathodic Plasma Source Nitriding

by Lei Zhang, Minghao Shao, Zhehao Zhang, Xuening Yi, Jiwen Yan, Zelong Zhou, Dazhen Fang, Yongyong He and Yang Li

Materials 2023, 16(8), 2961; https://doi.org/10.3390/ma16082961 - 7 Apr 2023

Cited by 7 | Viewed by 1649

Abstract

Ti6Al4V titanium alloys, with high specific strength and good biological compatibility with the human body, are ideal materials for medical surgical implants. However, Ti6Al4V titanium alloys are prone to corrosion in the human environment, which affects the service life of implants and harms [...] Read more.

Ti6Al4V titanium alloys, with high specific strength and good biological compatibility with the human body, are ideal materials for medical surgical implants. However, Ti6Al4V titanium alloys are prone to corrosion in the human environment, which affects the service life of implants and harms human health. In this work, hollow cathode plasm source nitriding (HCPSN) was used to generate nitrided layers on the surfaces of Ti6Al4V titanium alloys to improve their corrosion resistance. Ti6Al4V titanium alloys were nitrided in NH₃ at 510 °C for 0, 1, 2, and 4 h. The microstructure and phase composition of the Ti-N nitriding layer was characterized by high-resolution transmission electron microscopy, atomic force microscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. This modified layer was identified to be composed of TiN, Ti₂N, and α-Ti (N) phase. To study the corrosion properties of different phases, the nitriding 4 h samples were mechanically ground and polished to obtain the various surfaces of Ti₂N and α-Ti (N) phases. The potentiodynamic polarization and electrochemical impedance measurements were conducted in Hank’s solution to characterize the corrosion resistance of Ti-N nitriding layers in the human environment. The relationship between corrosion resistance and the microstructure of the Ti-N nitriding layer was discussed. The new Ti-N nitriding layer that can improve corrosion resistance provides a broader prospect for applying Ti6Al4V titanium alloy in the medical field. Full article

(This article belongs to the Special Issue Surface Engineering & Coating Technologies for Corrosion and Tribocorrosion Resistance)

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23 pages, 8504 KiB

Open AccessEditor’s ChoiceArticle

Scratch and Wear Behaviour of Co-Cr-Mo Alloy in Ringer’s Lactate Solution

by Raimundo Silva, Marcos Dantas dos Santos, Rui Madureira, Rui Soares, Rui Neto, Ângela Aparecida Vieira, Polyana Alves Radi Gonçalves, Priscila Maria Sarmeiro M. Leite, Lúcia Vieira and Filomena Viana

Materials 2023, 16(7), 2923; https://doi.org/10.3390/ma16072923 - 6 Apr 2023

Cited by 3 | Viewed by 1569

Abstract

Cobalt–chromium–molybdenum (Co-Cr-Mo) alloy is a material recommended for biomedical implants; however, to be suitable for this application, it should have good tribological properties, which are related to grain size. This paper investigates the tribological behaviour of a Co-Cr-Mo alloy produced using investment casting, [...] Read more.

Cobalt–chromium–molybdenum (Co-Cr-Mo) alloy is a material recommended for biomedical implants; however, to be suitable for this application, it should have good tribological properties, which are related to grain size. This paper investigates the tribological behaviour of a Co-Cr-Mo alloy produced using investment casting, together with electromagnetic stirring, to reduce its grain size. The samples were subjected to wear and scratch tests in simulated body fluid (Ringer’s lactate solution). Since a reduction in grain size can influence the behaviour of the material, in terms of resistance and tribological response, four samples with different grain sizes were produced for use in our investigation of the behaviour of the alloy, in which we considered the friction coefficient, wear, and scratch resistance. The experiments were performed using a tribometer, with mean values for the friction coefficient, normal load, and tangential force acquired and recorded by the software. Spheres of Ti-6Al-4V and 316L steel were used as counterface materials. In addition, to elucidate the influence of grain size on the mechanical properties of the alloy, observations were conducted via scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD). The results showed changes in the structure, with a reduction in grain size from 5.51 to 0.79 mm. Using both spheres, the best results for the friction coefficient and wear volume corresponded to the sample with the smallest grain size of 0.79 mm. The friction coefficients obtained were 0.37 and 0.45, using the Ti-6Al-4V and 316L spheres, respectively. These results confirm that the best surface finish for Co-Cr-Mo alloy used as a biomedical implant is one with a smaller grain size, since this results in a lower friction coefficient and low wear. Full article

(This article belongs to the Section Metals and Alloys)

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17 pages, 4149 KiB

Open AccessEditor’s ChoiceArticle

Sustainable Innovation: Turning Waste into Soil Additives

by Daria Marczak, Krzysztof Lejcuś, Iwona Lejcuś and Jakub Misiewicz

Materials 2023, 16(7), 2900; https://doi.org/10.3390/ma16072900 - 6 Apr 2023

Cited by 4 | Viewed by 1757

Abstract

In recent years, a dynamic increase in environmental pollution with textile waste has been observed. Natural textile waste has great potential for environmental applications. This work identifies potential ways of sustainably managing natural textile waste, which is problematic waste from sheep farming or [...] Read more.

In recent years, a dynamic increase in environmental pollution with textile waste has been observed. Natural textile waste has great potential for environmental applications. This work identifies potential ways of sustainably managing natural textile waste, which is problematic waste from sheep farming or the cultivation of fibrous plants. On the basis of textile waste, an innovative technology was developed to support water saving and plant vegetation- biodegradable water-absorbing geocomposites (BioWAGs). The major objective of this study was to determine BioWAG effectiveness under field conditions. The paper analyses the effect of BioWAGs on the increments in fresh and dry matter, the development of the root system, and the relative water content (RWC) of selected grass species. The conducted research confirmed the high efficiency of the developed technology. The BioWAGs increased the fresh mass of grass shoots by 230-420% and the root system by 130-200% compared with the control group. The study proved that BioWAGs are a highly effective technology that supports plant vegetation and saves water. Thanks to the reuse of waste materials, the developed technology is compatible with the assumptions of the circular economy and the goals of sustainable development. Full article

(This article belongs to the Section Green Materials)

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20 pages, 14100 KiB

Open AccessEditor’s ChoiceArticle

Effect of Process Parameters on the Microstructure and Properties of Cu–Cr–Nb–Ti Alloy Manufactured by Selective Laser Melting

by Jian Li, Zuming Liu, Huan Zhou, Shupeng Ye, Yazhou Zhang, Tao Liu, Daoyan Jiang, Lei Chen and Runxing Zhou

Materials 2023, 16(7), 2912; https://doi.org/10.3390/ma16072912 - 6 Apr 2023

Cited by 2 | Viewed by 1710

Abstract

The fabrication of high-performance copper alloys by selective laser melting (SLM) is challenging, and establishing relationships between the process parameters and microstructures is necessary. In this study, Cu–Cr–Nb–Ti alloy is manufactured by SLM, and the microstructures of the alloy are investigated by X-ray [...] Read more.

The fabrication of high-performance copper alloys by selective laser melting (SLM) is challenging, and establishing relationships between the process parameters and microstructures is necessary. In this study, Cu–Cr–Nb–Ti alloy is manufactured by SLM, and the microstructures of the alloy are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). The effects of processing parameters such as laser power and scanning speed on the relative density, defects, microstructures, mechanical properties, and electrical conductivity of the Cu–Cr–Nb–Ti alloy are studied. The optimal processing window for fabricating Cu–Cr–Nb–Ti alloy by SLM is determined. Face-centered cubic (FCC) Cu diffraction peaks shifting to small angles are observed, and there are no diffraction peaks related to the second phase. The grains of XY planes have a bimodal distribution with an average grain size of 24–55 μm. Fine second phases with sizes of less than 50 nm are obtained. The microhardness, tensile strength, and elongation of the Cu–Cr–Nb–Ti alloy manufactured using the optimum processing parameters, laser power of 325 W and scanning speed of 800 mm/s, are 139 HV0.2, 416 MPa, and 27.8%, respectively, and the electrical conductivity is 15.6% IACS (International Annealed Copper Standard). This study provides a feasible scheme for preparing copper alloys with excellent performance and complex geometries. Full article

(This article belongs to the Special Issue 3D Printing of Metallic Materials)

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15 pages, 4461 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Mg-Impurities in Raw Materials on the Synthesis of Rankinite Clinker and the Strength of Mortar Hardening in CO₂ Environment

by Raimundas Siauciunas, Edita Prichockiene and Zenonas Valancius

Materials 2023, 16(7), 2930; https://doi.org/10.3390/ma16072930 - 6 Apr 2023

Cited by 1 | Viewed by 1219

Abstract

The idea of this work is to reduce the negative effect of ordinary Portland cement (OPC) manufacture on the environment by decreasing clinker production temperature and developing an alternative rankinite binder that hardens in the CO₂ atmosphere. The common OPC raw materials, [...] Read more.

The idea of this work is to reduce the negative effect of ordinary Portland cement (OPC) manufacture on the environment by decreasing clinker production temperature and developing an alternative rankinite binder that hardens in the CO₂ atmosphere. The common OPC raw materials, limestone and mica clay, if they contain a higher MgO content, have been found to be unsuitable for the synthesis of CO₂-curing low-lime binders. X-ray diffraction analysis (ex-situ and in-situ in the temperature range of 25–1150 °C) showed that akermanite Ca₂Mg(Si₂O₇) begins to form at a temperature of 900 °C. According to Rietveld refinement, the interlayer distances of the resulting curve are more accurately described by the compound, which contains intercalated Fe²⁺ and Al³⁺ ions and has the chemical formula Ca₂(MgO_0.495·FeO_0.202·AlO_0.303)·(FeO_0.248·AlO·Si_1.536·O₇). Stoichiometric calculations showed that FeO and Al₂O₃ have replaced about half of the MgO content in the akermanite structure. All this means that only ~4 wt% MgO content in the raw materials determines that ~60 wt% calcium magnesium silicates are formed in the synthesis product. Moreover, it was found that the formed akermanite practically does not react with CO₂. Within 24 h of interaction with 99.9 wt% of CO₂ gas (15 bar), the intensity of the akermanite peaks does not practically change at 25 °C; no changes are observed at 45 °C, either, which means that the chemical reaction does not take place. As a result, the compressive strength of the samples compressed from the synthesized product and CEN Standard sand EN 196-1 (1:3), and hardened at 15 bar CO₂, 45 °C for 24 h, was only 14.45 MPa, while the analogous samples made from OPC clinker obtained from the same raw materials yielded 67.5 MPa. Full article

(This article belongs to the Special Issue Advances in Sustainable Civil Engineering Materials)

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16 pages, 3865 KiB

Open AccessEditor’s ChoiceArticle

Photoacoustic Characterization of TiO₂ Thin-Films Deposited on Silicon Substrate Using Neural Networks

by Katarina Lj Djordjević, Dragana K. Markushev, Marica N. Popović, Mioljub V. Nesić, Slobodanka P. Galović, Dragan V. Lukić and Dragan D. Markushev

Materials 2023, 16(7), 2865; https://doi.org/10.3390/ma16072865 - 4 Apr 2023

Cited by 1 | Viewed by 1142

Abstract

In this paper, the possibility of determining the thermal, elastic and geometric characteristics of a thin TiO₂ film deposited on a silicon substrate, with a thickness of 30 μm, in the frequency range of 20 to 20 kHz with neural networks were [...] Read more.

In this paper, the possibility of determining the thermal, elastic and geometric characteristics of a thin TiO₂ film deposited on a silicon substrate, with a thickness of 30 μm, in the frequency range of 20 to 20 kHz with neural networks were analysed. For this purpose, the geometric (thickness), thermal (thermal diffusivity, coefficient of linear expansion) and electronic parameters of substrates were known and constant in the two-layer model, while the following nano-layer thin-film parameters were changed: thickness, expansion and thermal diffusivity. Predictions of these three parameters of the thin-film were analysed separately with three neural networks. All of them together were joined by a fourth neural network. It was shown that the neural network, which analysed all three parameters at the same time, achieved the highest accuracy, so the use of networks that provide predictions for only one parameter is less reliable. The obtained results showed that the application of neural networks in determining the thermoelastic properties of a thin film on a supporting substrate enables the estimation of its characteristics with great accuracy. Full article

(This article belongs to the Special Issue Characterization of Thin Films and Superlattice Using Thermal Wave Methods)

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12 pages, 3387 KiB

Open AccessEditor’s ChoiceArticle

Negative Magnetoresistance in Hopping Regime of Lightly Doped Thermoelectric SnSe

by Marija Zorić, Naveen Singh Dhami, Kristian Bader, Peter Gille, Ana Smontara and Petar Popčević

Materials 2023, 16(7), 2863; https://doi.org/10.3390/ma16072863 - 4 Apr 2023

Cited by 1 | Viewed by 1440

Abstract

Semiconducting SnSe, an analog of black phosphorus, recently attracted great scientific interest due to a disputed report of a large thermoelectric figure of merit, which has not been reproduced subsequently. Here we concentrate on the low-temperature ground state. To gain a better understanding [...] Read more.

Semiconducting SnSe, an analog of black phosphorus, recently attracted great scientific interest due to a disputed report of a large thermoelectric figure of merit, which has not been reproduced subsequently. Here we concentrate on the low-temperature ground state. To gain a better understanding of the system, we present magneto-transport properties in high-quality single crystals of as-grown, lightly doped SnSe down to liquid helium temperatures. We show that SnSe behaves as a p-type doped semiconductor in the vicinity of a metal-insulator transition. Electronic transport at the lowest temperatures is dominated by the hopping mechanism. Negative magnetoresistance at low fields is well described by antilocalization, while positive magnetoresistance at higher fields is consistent with the shrinkage of localized impurity wavefunctions. At higher temperatures, a dilute metallic regime is realized where elusive T² and B² resistivity dependence is observed, posing a challenge to theoretical comprehension of the underlying physical mechanism. Full article

(This article belongs to the Special Issue New Insights into Metal–Insulator Transitions)

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25 pages, 40744 KiB

Open AccessEditor’s ChoiceArticle

A Bond-Based Peridynamic Model with Matrix Plasticity for Impact Damage Analysis of Composite Materials

by Mingwei Sun, Lisheng Liu, Hai Mei, Xin Lai, Xiang Liu and Jing Zhang

Materials 2023, 16(7), 2884; https://doi.org/10.3390/ma16072884 - 4 Apr 2023

Viewed by 1255

Abstract

The prediction of damage and failure to fiber-reinforced polymer composites in extreme environments, particularly when subjected to impact loading, is a crucial issue for the application and design of protective structures. In this paper, based on the prototype microelastic brittle (PMB) model and [...] Read more.

The prediction of damage and failure to fiber-reinforced polymer composites in extreme environments, particularly when subjected to impact loading, is a crucial issue for the application and design of protective structures. In this paper, based on the prototype microelastic brittle (PMB) model and the LaRC05 composite materials failure model, we proposed a bond-based peridynamic (BB-PD) model with the introduction of plastic hardening of the resin matrix for fiber-reinforced polymer composites. The PD constitutive relationships of the matrix bond and interlayer bond under compressive loading are considered to include two stages of linear elasticity and plastic hardening, according to the stress–strain relationship of the resin matrix in the LaRC05 failure model. The proposed PD model is employed to simulate the damage behaviors of laminated composites subjected to impact loading. The corresponding ballistic impact tests of composite laminates were carried out to observe their damage behaviors. The PD prediction results are in good agreement with the ballistic experimental results, which can verify the correctness and accuracy of the PD model developed in this study in describing the impact damage behaviors of composite materials. In addition, the characteristics and degree of damage in composite laminates are analyzed and discussed based on this PD model. The difference in the impact resistance of composite laminates with different stacking sequences is also studied using the numerical simulation results. Full article

(This article belongs to the Special Issue Computational Fracture and Damage Modeling of Engineered Materials)

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25 pages, 4830 KiB

Open AccessEditor’s ChoiceReview

Semiconductor Characterization by Terahertz Excitation Spectroscopy

by Arūnas Krotkus, Ignas Nevinskas and Ričardas Norkus

Materials 2023, 16(7), 2859; https://doi.org/10.3390/ma16072859 - 3 Apr 2023

Cited by 3 | Viewed by 1970

Abstract

Surfaces of semiconducting materials excited by femtosecond laser pulses emit electromagnetic waves in the terahertz (THz) frequency range, which by definition is the 0.1–10 THz region. The nature of terahertz radiation pulses is, in the majority of cases, explained by the appearance of [...] Read more.

Surfaces of semiconducting materials excited by femtosecond laser pulses emit electromagnetic waves in the terahertz (THz) frequency range, which by definition is the 0.1–10 THz region. The nature of terahertz radiation pulses is, in the majority of cases, explained by the appearance of ultrafast photocurrents. THz pulse duration is comparable with the photocarrier momentum relaxation time, thus such hot-carrier effects as the velocity overshoot, ballistic carrier motion, and optical carrier alignment must be taken into consideration when explaining experimental observations of terahertz emission. Novel commercially available tools such as optical parametric amplifiers that are capable of generating femtosecond optical pulses within a wide spectral range allow performing new unique experiments. By exciting semiconductor surfaces with various photon energies, it is possible to look into the ultrafast processes taking place at different electron energy levels of the investigated materials. The experimental technique known as the THz excitation spectroscopy (TES) can be used as a contactless method to study the band structure and investigate the ultrafast processes of various technologically important materials. A recent decade of investigations with the THz excitation spectroscopy method is reviewed in this article. TES experiments performed on the common bulk A3B5 compounds such as the wide-gap GaAs, and narrow-gap InAs and InSb, as well as Ge, Te, GaSe and other bulk semiconductors are reviewed. Finally, the results obtained by this non-contact technique on low-dimensional materials such as ultrathin mono-elemental Bi films, InAs, InGaAs, and GaAs nanowires are also presented. Full article

(This article belongs to the Special Issue Laser and Plasma Technologies in Materials Science: Physics and Applications)

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17 pages, 10932 KiB

Open AccessEditor’s ChoiceArticle

Photoluminescence and Photocatalytic Properties of MWNTs Decorated with Fe-Doped ZnO Nanoparticles

by Adriana Popa, Maria Stefan, Sergiu Macavei, Laura Elena Muresan, Cristian Leostean, Cornelia Veronica Floare-Avram and Dana Toloman

Materials 2023, 16(7), 2858; https://doi.org/10.3390/ma16072858 - 3 Apr 2023

Cited by 3 | Viewed by 1658

Abstract

The present work reports the photoluminescence (PL) and photocatalytic properties of multi-walled carbon nanotubes (MWCNTs) decorated with Fe-doped ZnO nanoparticles. MWCNT:ZnO-Fe nanocomposite samples with weight ratios of 1:3, 1:5 and 1:10 were prepared using a facile synthesis method. The obtained crystalline phases were [...] Read more.

The present work reports the photoluminescence (PL) and photocatalytic properties of multi-walled carbon nanotubes (MWCNTs) decorated with Fe-doped ZnO nanoparticles. MWCNT:ZnO-Fe nanocomposite samples with weight ratios of 1:3, 1:5 and 1:10 were prepared using a facile synthesis method. The obtained crystalline phases were evidenced by X-ray diffraction (XRD). X-ray Photoelectron spectroscopy (XPS) revealed the presence of both 2+ and 3+ valence states of Fe ions in a ratio of approximately 0.5. The electron paramagnetic resonance EPR spectroscopy sustained the presence of Fe³⁺ ions in the ZnO lattice and evidenced oxygen vacancies. Transmission electron microscopy (TEM) images showed the attachment and distribution of Fe-doped ZnO nanoparticles along the nanotubes with a star-like shape. All of the samples exhibited absorption in the UV region, and the absorption edge was shifted toward a higher wavelength after the addition of MWCNT component. The photoluminescence emission spectra showed peaks in the UV and visible region. Visible emissions are a result of the presence of defects or impurity states in the material. All of the samples showed photocatalytic activity against the Rhodamine B (RhB) synthetic solution under UV irradiation. The best performance was obtained using the MWCNT:ZnO-Fe(1:5) nanocomposite samples, which exhibited a 96% degradation efficiency. The mechanism of photocatalytic activity was explained based on the reactive oxygen species generated by the nanocomposites under UV irradiation in correlation with the structural and optical information obtained in this study. Full article

(This article belongs to the Special Issue Advanced Luminescent Materials and Devices)

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16 pages, 4309 KiB

Open AccessEditor’s ChoiceArticle

Solar-Driven Thermocatalytic Synthesis of Octahydroquinazolinone Using Novel Polyvinylchloride (PVC)-Supported Aluminum Oxide (Al₂O₃) Catalysts

by Abdulrahman I. Alharthi, Mshari A. Alotaibi, Amani M. Alansi, Talal F. Qahtan, Imtiaz Ali, Matar N. Al-Shalwi and Md. Afroz Bakht

Materials 2023, 16(7), 2835; https://doi.org/10.3390/ma16072835 - 2 Apr 2023

Viewed by 1153

Abstract

The chemical industry is one of the main fossil fuel consumers, so its reliance on sustainable and renewable resources such as wind and solar energy should be increased to protect the environment. Accordingly, solar-driven thermocatalytic synthesis of octahydroquinazolinone using polyvinylchloride (PVC)-supported aluminum oxide [...] Read more.

The chemical industry is one of the main fossil fuel consumers, so its reliance on sustainable and renewable resources such as wind and solar energy should be increased to protect the environment. Accordingly, solar-driven thermocatalytic synthesis of octahydroquinazolinone using polyvinylchloride (PVC)-supported aluminum oxide (Al₂O₃) as a catalyst under natural sunlight is proposed in this work. The Al₂O₃/PVC catalysts were characterized by FT-IR, SEM, BET, XRD, and XPS techniques. The obtained results indicate that the yield and reaction time can be modified by adjusting the molar ratio of the catalyst. To investigate the stability of the catalyst, the spent catalyst was reused in several reactions. The results indicated that, when a 50% Al₂O₃ catalyst is employed in an absolute solar heat, it performs exceptionally well in terms of yield (98%) and reaction time (35 min). Furthermore, the reaction times and yield of octahydroquinazolinone derivatives with an aryl moiety were superior to those of heteroaryl. All the synthesized compounds were well characterized by FT-IR, ¹H-NMR, and ¹³C-NMR. The current work introduces a new strategy to use solar heat for energy-efficient chemical reactions using a cost-effective, recyclable environmentally friendly PVC/Al₂O₃ catalyst that produces a high yield. Full article

(This article belongs to the Special Issue Asymmetric/Heterogeneous Catalysis and Green Organic Synthesis)

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22 pages, 5544 KiB

Open AccessEditor’s ChoiceReview

Recent Advances of Indium Oxide-Based Catalysts for CO₂ Hydrogenation to Methanol: Experimental and Theoretical

by Dongren Cai, Yanmei Cai, Kok Bing Tan and Guowu Zhan

Materials 2023, 16(7), 2803; https://doi.org/10.3390/ma16072803 - 31 Mar 2023

Cited by 6 | Viewed by 3392

Abstract

Methanol synthesis from the hydrogenation of carbon dioxide (CO₂) with green H₂ has been proven as a promising method for CO₂ utilization. Among the various catalysts, indium oxide (In₂O₃)-based catalysts received tremendous research interest due [...] Read more.

Methanol synthesis from the hydrogenation of carbon dioxide (CO₂) with green H₂ has been proven as a promising method for CO₂ utilization. Among the various catalysts, indium oxide (In₂O₃)-based catalysts received tremendous research interest due to the excellent methanol selectivity with appreciable CO₂ conversion. Herein, the recent experimental and theoretical studies on In₂O₃-based catalysts for thermochemical CO₂ hydrogenation to methanol were systematically reviewed. It can be found that a variety of steps, such as the synthesis method and pretreatment conditions, were taken to promote the formation of oxygen vacancies on the In₂O₃ surface, which can inhibit side reactions to ensure the highly selective conversion of CO₂ into methanol. The catalytic mechanism involving the formate pathway or carboxyl pathway over In₂O₃ was comprehensively explored by kinetic studies, in situ and ex situ characterizations, and density functional theory calculations, mostly demonstrating that the formate pathway was extremely significant for methanol production. Additionally, based on the cognition of the In₂O₃ active site and the reaction path of CO₂ hydrogenation over In₂O₃, strategies were adopted to improve the catalytic performance, including (i) metal doping to enhance the adsorption and dissociation of hydrogen, improve the ability of hydrogen spillover, and form a special metal-In₂O₃ interface, and (ii) hybrid with other metal oxides to improve the dispersion of In₂O₃, enhance CO₂ adsorption capacity, and stabilize the key intermediates. Lastly, some suggestions in future research were proposed to enhance the catalytic activity of In₂O₃-based catalysts for methanol production. The present review is helpful for researchers to have an explicit version of the research status of In₂O₃-based catalysts for CO₂ hydrogenation to methanol and the design direction of next-generation catalysts. Full article

(This article belongs to the Special Issue Nanocatalysts for CO₂ Utilization)

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18 pages, 6651 KiB

Open AccessEditor’s ChoiceArticle

Surface Cement Concrete with Reclaimed Asphalt

by Małgorzata Linek, Magdalena Bacharz and Patrycja Piotrowska

Materials 2023, 16(7), 2791; https://doi.org/10.3390/ma16072791 - 31 Mar 2023

Cited by 1 | Viewed by 1130

Abstract

This research concerns the possibility of using reclaimed asphalt pavement as a substitute for conventional aggregate in cement concrete mixtures for roads and airfield applications. The advantages of using reclaimed asphalt pavement as a replacement for natural aggregates are presented. Economic and environmental [...] Read more.

This research concerns the possibility of using reclaimed asphalt pavement as a substitute for conventional aggregate in cement concrete mixtures for roads and airfield applications. The advantages of using reclaimed asphalt pavement as a replacement for natural aggregates are presented. Economic and environmental aspects are indicated, including the reduction in the consumption of natural non-renewable sources of mineral aggregates, as well as reduction in transport costs and emissions of harmful greenhouse gases. The consistency of this recycled material with the idea of sustainable development in the construction industry is emphasized. The test results of the used reclaimed asphalt and the assessment of the effect of its amount on the change in mechanical, physical and strength parameters of cement concrete are presented. It has been shown that the addition of reclaimed concrete reduces selected parameters of cement concrete, but it is possible to use it in structures with less traffic load, taking into account the sustainable development policy. Full article

(This article belongs to the Special Issue Advanced Materials – Microstructure, Manufacturing and Analysis)

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19 pages, 5451 KiB

Open AccessEditor’s ChoiceArticle

Heat Transfer Analysis of Warm Guss Asphalt Concrete for Mini-Trench Overlaying

by Kyung-Nam Kim, Yeong-Min Kim, Sang-Yum Lee and Tri Ho Minh Le

Materials 2023, 16(7), 2808; https://doi.org/10.3390/ma16072808 - 31 Mar 2023

Viewed by 1215

Abstract

Conventional hot mix asphalt overlaying on trench infrastructure typically necessitates extended cooling times for further works and can have adverse effects on buried components, such as electricity cables and hot water pipes. Therefore, this research aims to investigate the use of warm guss [...] Read more.

Conventional hot mix asphalt overlaying on trench infrastructure typically necessitates extended cooling times for further works and can have adverse effects on buried components, such as electricity cables and hot water pipes. Therefore, this research aims to investigate the use of warm guss mastic asphalt (at an installation temperature of 160 °C) as an overlaying material for mini-trenches, which can reduce the cooling time required for traffic opening and improve the efficiency of the construction process. This research involved two stages: first, lab testing and related research results were used to generate the thermal conductivity and specific heat necessary for simulation work. Second, a finite element model analysis was conducted to evaluate the thermal transmission of the overlaying surface and the buried conduit based on the summer pavement temperature distribution through the Korean Pavement Research Program. Afterward, the field test bed was constructed to verify the simulation. The results indicate that the optimal thickness of the overlaying material and the concrete covering should be designed to ensure thermal durability and meet traffic opening requirements. The overlaying depth of the mini trench using warm mix guss mastic asphalt should be less than 100 mm to meet with the traffic opening time, while the thickness of the concrete covering should be designed to be more than 100 mm to ensure thermal durability. Additionally, the findings suggest that the application of warm guss asphalt could reduce the opening time by 30 min to 1 h and 25 min compared to conventional hot guss asphalt materials. When the pavement surface temperature for the traffic opening is controlled at 50 °C, the asphalt mixture requires at least 2 h to 5 h to meet the cooling criteria for traffic opening, respectively. Overall, this research confirms the potential benefits and optimal use of warm guss mastic asphalt in the construction process of mini-trenches. Full article

(This article belongs to the Special Issue Sustainable Asphalt Pavements: Materials, Design Methods, and Characterization Techniques (Second Volume))

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18 pages, 14569 KiB

Open AccessEditor’s ChoiceArticle

Effect of Graphene Oxide on the Mechanical Properties and Durability of High-Strength Lightweight Concrete Containing Shale Ceramsite

by Xiaojiang Hong, Jin Chai Lee, Jing Lin Ng, Zeety Md Yusof, Qian He and Qiansha Li

Materials 2023, 16(7), 2756; https://doi.org/10.3390/ma16072756 - 30 Mar 2023

Cited by 5 | Viewed by 1608

Abstract

An effective pathway to achieve the sustainable development of resources and environmental protection is to utilize shale ceramsite (SC), which is processed from shale spoil to produce high-strength lightweight concrete (HSLWC). Furthermore, the urgent demand for better performance of HSLWC has stimulated active [...] Read more.

An effective pathway to achieve the sustainable development of resources and environmental protection is to utilize shale ceramsite (SC), which is processed from shale spoil to produce high-strength lightweight concrete (HSLWC). Furthermore, the urgent demand for better performance of HSLWC has stimulated active research on graphene oxide (GO) in strengthening mechanical properties and durability. This study was an effort to investigate the effect of different contents of GO on HSLWC manufactured from SC. For this purpose, six mixtures containing GO in the range of 0–0.08% (by weight of cement) were systematically designed to test the mechanical properties (compressive strength, flexural strength, and splitting tensile strength), durability (chloride penetration resistance, freezing–thawing resistance, and sulfate attack resistance), and microstructure. The experimental results showed that the optimum amount of 0.05% GO can maximize the compressive strength, flexural strength, and splitting tensile strength by 20.1%, 34.3%, and 24.2%, respectively, and exhibited excellent chloride penetration resistance, freezing–thawing resistance, and sulfate attack resistance. Note that when the addition of GO was relatively high, the performance improvement in HSLWC as attenuated instead. Therefore, based on the comprehensive analysis of microstructure, the optimal addition level of GO to achieve the best mechanical properties and durability of HSLWC is considered to be 0.05%. These findings can provide a new method for the use of SC in engineering. Full article

(This article belongs to the Special Issue Advanced Graphene and Graphene Oxide Materials)

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14 pages, 6521 KiB

Open AccessEditor’s ChoiceArticle

The Impact of Excitation Periods on the Outcome of Lock-In Thermography

by Milan Sapieta, Vladimír Dekýš, Peter Kopas, Lenka Jakubovičová and Zdenko Šavrnoch

Materials 2023, 16(7), 2763; https://doi.org/10.3390/ma16072763 - 30 Mar 2023

Cited by 2 | Viewed by 1014

Abstract

Thermal imaging is a non-destructive test method that uses an external energy source, such as a halogen lamp or flash lamp, to excite the material under test and measure the resulting temperature distribution. One of the important parameters of lock-in thermography is the [...] Read more.

Thermal imaging is a non-destructive test method that uses an external energy source, such as a halogen lamp or flash lamp, to excite the material under test and measure the resulting temperature distribution. One of the important parameters of lock-in thermography is the number of excitation periods, which is used to calculate a phase image that shows defects or inhomogeneities in the material. The results for multiple periods can be averaged, which leads to noise suppression, but the use of a larger number of periods may cause an increase in noise due to unsynchronization of the camera and the external excitation source or may lead to heating and subsequent damage to the sample. The phase image is the most common way of representing the results of lock-in thermography, but amplitude images and complex images can also be obtained. In this study, eight measurements were performed on different samples using a thermal pulse source (flash lamp and halogen lamp) with a period of 120 s. For each sample, five phase images were calculated using different number of periods, preferably one to five periods. The phase image calculated from one period was used as a reference. To determine the effect of the number of excitation periods on the phase image, the reference phase image for one period was compared with the phase images calculated using multiple periods using the structural similarity index (SSIM) and multi-scale SSIM (MS-SSIM). Full article

(This article belongs to the Special Issue Newer Paradigms in Advanced Materials Characterisation)

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10 pages, 5490 KiB

Open AccessEditor’s ChoiceArticle

The Heteroepitaxy of Thick β-Ga₂O₃ Film on Sapphire Substrate with a β-(Al_xGa_1−x)₂O₃ Intermediate Buffer Layer

by Wenhui Zhang, Hezhi Zhang, Song Zhang, Zishi Wang, Litao Liu, Qi Zhang, Xibing Hu and Hongwei Liang

Materials 2023, 16(7), 2775; https://doi.org/10.3390/ma16072775 - 30 Mar 2023

Cited by 1 | Viewed by 1453

Abstract

A high aluminum (Al) content β-(Al_xGa_1−x)₂O₃ film was synthesized on c-plane sapphire substrate using the gallium (Ga) diffusion method. The obtained β-(Al_xGa_1−x)₂O₃ film had an average thickness [...] Read more.

A high aluminum (Al) content β-(Al_xGa_1−x)₂O₃ film was synthesized on c-plane sapphire substrate using the gallium (Ga) diffusion method. The obtained β-(Al_xGa_1−x)₂O₃ film had an average thickness of 750 nm and a surface roughness of 2.10 nm. Secondary ion mass spectrometry results indicated the homogenous distribution of Al components in the film. The Al compositions in the β-(Al_xGa_1−x)₂O₃ film, as estimated by X-ray diffraction, were close to those estimated by X-ray photoelectron spectroscopy, at ~62% and ~61.5%, respectively. The bandgap of the β-(Al_xGa_1−x)₂O₃ film, extracted from the O 1s core-level spectra, was approximately 6.0 ± 0.1 eV. After synthesizing the β-(Al_xGa_1−x)₂O₃ film, a thick β-Ga₂O₃ film was further deposited on sapphire substrate using carbothermal reduction and halide vapor phase epitaxy. The β-Ga₂O₃ thick film, grown on a sapphire substrate with a β-(Al_xGa_1−x)₂O₃ buffer layer, exhibited improved crystal orientation along the (-201) plane. Moreover, the scanning electron microscopy revealed that the surface quality of the β-Ga₂O₃ thick film on sapphire substrate with a β-(Al_xGa_1−x)₂O₃ intermediate buffer layer was significantly improved, with an obvious transition from grain island-like morphology to 2D continuous growth, and a reduction in surface roughness to less than 10 nm. Full article

(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)

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22 pages, 8107 KiB

Open AccessEditor’s ChoiceReview

Sol–Gel Photonic Glasses: From Material to Application

by Giancarlo C. Righini, Cristina Armellini, Maurizio Ferrari, Alice Carlotto, Alessandro Carpentiero, Andrea Chiappini, Alessandro Chiasera, Anna Lukowiak, Thi Ngoc Lam Tran and Stefano Varas

Materials 2023, 16(7), 2724; https://doi.org/10.3390/ma16072724 - 29 Mar 2023

Cited by 3 | Viewed by 2030

Abstract

In this review, we present a short overview of the development of sol–gel glasses for application in the field of photonics, with a focus on some of the most interesting results obtained by our group and collaborators in that area. Our main attention [...] Read more.

In this review, we present a short overview of the development of sol–gel glasses for application in the field of photonics, with a focus on some of the most interesting results obtained by our group and collaborators in that area. Our main attention is devoted to silicate glasses of different compositions, which are characterized by specific optical and spectroscopic properties for various applications, ranging from luminescent systems to light-confining structures and memristors. In particular, the roles of rare-earth doping, matrix composition, the densification process and the fabrication protocol on the structural, optical and spectroscopic properties of the developed photonic systems are discussed through appropriate examples. Some achievements in the fabrication of oxide sol–gel optical waveguides and of micro- and nanostructures for the confinement of light are also briefly discussed. Full article

(This article belongs to the Special Issue Glassy Materials: From Preparation to Application)

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11 pages, 4074 KiB

Open AccessEditor’s ChoiceArticle

Optimization of the Winding Layer Structure of High-Pressure Composite Overwrapped Pressure Vessels

by Chengrui Di, Bo Zhu, Xiangji Guo, Junwei Yu, Yanbin Zhao and Kun Qiao

Materials 2023, 16(7), 2713; https://doi.org/10.3390/ma16072713 - 29 Mar 2023

Cited by 4 | Viewed by 1425

Abstract

The large thickness COPV is designed by netting theory and the finite element simulation method, but the actual performance is low and the cylinder performance still cannot be improved after increasing the thickness of the composite winding layer. This paper analyzes the reasons [...] Read more.

The large thickness COPV is designed by netting theory and the finite element simulation method, but the actual performance is low and the cylinder performance still cannot be improved after increasing the thickness of the composite winding layer. This paper analyzes the reasons for this and puts forward a feasible solution: without changing the thickness of the winding layer, the performance of COPV can be effectively increased by increasing the proportion of annular winding fiber. This method has been verified by tests and is supported by theory. Full article

(This article belongs to the Special Issue Additive Manufacturing of Composites, Volume II)

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17 pages, 11294 KiB

Open AccessEditor’s ChoiceArticle

Study on Perforation Behavior of PTFE/Al Reactive Material Composite Jet Impacting Steel Target

by Hongda Li, Hui Duan, Zhili Zhang and Yuanfeng Zheng

Materials 2023, 16(7), 2715; https://doi.org/10.3390/ma16072715 - 29 Mar 2023

Cited by 3 | Viewed by 1167

Abstract

To study the penetration and cratering effect of reactive material composite jets, a series of experiments are carried out for the shaped charge (SC) with different composite liners damaging steel targets. The inner layer of composite liners is metal and the outer one [...] Read more.

To study the penetration and cratering effect of reactive material composite jets, a series of experiments are carried out for the shaped charge (SC) with different composite liners damaging steel targets. The inner layer of composite liners is metal and the outer one is a polytetrafluoroethylene/aluminum (PTFE/Al) reactive material. Copper (Cu), titanium (Ti) and Al inner liners are used in this paper. The reactive material liner is composed of 73.5 wt.% PTFE and 26.5 wt.% Al powder through mass-matched ratios. Reactive material composite liners are prepared through machining, cold pressing and a sintering process. The SC mainly consists of a case, a composite liner, high-energy explosive and an initiator. The steel target is steel 45#, with a thickness of 66 mm. A standoff of 1.0 CD (charge diameter) is selected to conduct the penetration experiments. The experimental results show that when the inner layer of the composite liner is composed of Ti and Al, the hole diameters on the steel target formed by the reactive material composite jet are significantly larger than that of the inner Cu liner. By introducing the initiation delay time (τ) and detonation-like reaction model of PTFE/Al reactive materials, an integrated numerical simulation algorithm of the penetration and detonation-like effects of reactive material composite jets is realized. Numerical simulations demonstrate that the initial penetration holes on the steel targets are enlarged under the detonation-like effects of PTFE/Al reactive materials, and the simulated perforation sizes are in good agreement with the experimental results. Full article

(This article belongs to the Special Issue Dynamic Mechanical Analysis of Energetic Materials)

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14 pages, 6866 KiB

Open AccessEditor’s ChoiceArticle

Multifunctional TiO₂ Nanotube-Matrix Composites with Enhanced Photocatalysis and Lithium-Ion Storage Performances

by Mengmeng Zhang, Hui Li and Chunrui Wang

Materials 2023, 16(7), 2716; https://doi.org/10.3390/ma16072716 - 29 Mar 2023

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Abstract

As a multifunctional material, TiO₂ shows excellent performance in catalytic degradation and lithium-ion storage. However, high electron-hole pair recombination, poor conductivity, and low theoretical capacity severely limit the practical application of TiO₂. Herein, TiO₂ nanotube (TiO₂ NT) with [...] Read more.

As a multifunctional material, TiO₂ shows excellent performance in catalytic degradation and lithium-ion storage. However, high electron-hole pair recombination, poor conductivity, and low theoretical capacity severely limit the practical application of TiO₂. Herein, TiO₂ nanotube (TiO₂ NT) with a novel double-layer honeycomb structure were prepared by two-step electrochemical anodization. Honeycombed TiO₂ NT arrays possess clean top surfaces and a long-range ordering, which greatly facilitates the preparation of high-performance binary and ternary materials. A binary TiO₂ nanotube@Au nanoparticle (TiO₂ NT@Au NP) composite accompanied by appropriately concentrated and uniformly distributed gold particles was prepared in this work. Interestingly, the TiO₂ nanotube@Au nanoparticle (TiO₂ NT@Au NP) composites not only showed the excellent catalytic degradation effect of methylene blue, but also demonstrated large lithium-ion storage capacity (310.6 μAh cm⁻², 1.6 times of pristine TiO₂ NT). Based on the realization of the controllable fabrication of binary TiO₂ nanotube@MoS₂ nanosheet (TiO₂ NT@MoS₂ NS) composite, ternary TiO₂ nanotube@MoS₂ nanosheet@Au nanoparticle (TiO₂ NT@MoS₂ NS@Au NP) composite with abundant defects and highly ordered structure was also innovatively designed and fabricated. As expected, the TiO₂ NT@MoS₂ NS@Au NP anode exhibits extremely high initial discharge specific capacity (487.4 μAh cm⁻², 2.6 times of pristine TiO₂ NT) and excellent capacity retention (81.0%). Full article

(This article belongs to the Special Issue Advanced Nanomaterials and Mechanistic Studies for Energy Electrocatalysis)

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