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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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11 pages, 1889 KiB  
Article
Wall Shear Stress Analysis and Optimization in Tissue Engineering TPMS Scaffolds
by Tiago H. V. Pires, John W. C. Dunlop, André P. G. Castro and Paulo R. Fernandes
Materials 2022, 15(20), 7375; https://doi.org/10.3390/ma15207375 - 21 Oct 2022
Cited by 13 | Viewed by 2569
Abstract
When designing scaffolds for bone tissue engineering (BTE), the wall shear stress (WSS), due to the fluid flow inside the scaffold, is an important factor to consider as it influences the cellular process involved in new tissue formation. The present work analyzed the [...] Read more.
When designing scaffolds for bone tissue engineering (BTE), the wall shear stress (WSS), due to the fluid flow inside the scaffold, is an important factor to consider as it influences the cellular process involved in new tissue formation. The present work analyzed the average WSS in Schwartz diamond (SD) and gyroid (SG) scaffolds with different surface topologies and mesh elements using computational fluid dynamics (CFD) analysis. It was found that scaffold meshes with a smooth surface topology with tetrahedral elements had WSS levels 35% higher than the equivalent scaffold with a non-smooth surface topology with hexahedral elements. The present work also investigated the possibility of implementing the optimization algorithm simulated annealing to aid in the design of BTE scaffolds with a specific average WSS, with the outputs showing that the algorithm was able to reach WSS levels in the vicinity of 5 mPa (physiological range) within the established limit of 100 iterations. This proved the efficacy of combining CFD and optimization methods in the design of BTE scaffolds. Full article
(This article belongs to the Special Issue Design and Micromechanical Behavior of Orthopaedic Devices for Bone Repair and Regeneration)
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14 pages, 3715 KiB  
Article
Corrosion Crack Morphology and Creep Analysis of Members Based on Meso-Scale Corrosion Penetration
by Bin Zeng, Yiping Yang, Fuyuan Gong and Koichi Maekawa
Materials 2022, 15(20), 7338; https://doi.org/10.3390/ma15207338 - 20 Oct 2022
Cited by 4 | Viewed by 2012
Abstract
In this paper, to study the development of load-carrying capacity and long-term creep performance of reinforced concrete beams under different corrosion patterns, the rate-dependent model of concrete is used as the basis to consider the creep development process from the meso-scale level. The [...] Read more.
In this paper, to study the development of load-carrying capacity and long-term creep performance of reinforced concrete beams under different corrosion patterns, the rate-dependent model of concrete is used as the basis to consider the creep development process from the meso-scale level. The porosity mechanics method is used to simulate the generation and penetration process of corrosion products. Three corrosion conditions are set: bottom longitudinal reinforcement corrosion, top longitudinal reinforcement corrosion and all reinforcement corrosion. The corrosion rate is used as the variable in each corrosion condition. The results show that: (1) the greater the corrosion rate in all conditions, the lower the bearing capacity. In addition, the corrosion of top longitudinal reinforcement causes the damage form of the beam to change to brittle damage; (2) the creep coefficient decreases with the increase in corrosion rate in all working conditions, but the main factor for this phenomenon is the obvious increase in initial deformation. Consequently, it is not suitable to follow the conventional creep concept (deformation development/initial deformation) for the development of plastic deformation of damaged members. It is more reasonable to use the global deflection to describe the long-term deformation of corrosion-damaged members. Full article
(This article belongs to the Special Issue Multi-Scale Structural Characterization of Cement-Based Composites)
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36 pages, 8306 KiB  
Review
Gallium Oxide for Gas Sensor Applications: A Comprehensive Review
by Jun Zhu, Zhihao Xu, Sihua Ha, Dongke Li, Kexiong Zhang, Hai Zhang and Jijun Feng
Materials 2022, 15(20), 7339; https://doi.org/10.3390/ma15207339 - 20 Oct 2022
Cited by 49 | Viewed by 7762
Abstract
Ga2O3 has emerged as a promising ultrawide bandgap semiconductor for numerous device applications owing to its excellent material properties. In this paper, we present a comprehensive review on major advances achieved over the past thirty years in the field of [...] Read more.
Ga2O3 has emerged as a promising ultrawide bandgap semiconductor for numerous device applications owing to its excellent material properties. In this paper, we present a comprehensive review on major advances achieved over the past thirty years in the field of Ga2O3-based gas sensors. We begin with a brief introduction of the polymorphs and basic electric properties of Ga2O3. Next, we provide an overview of the typical preparation methods for the fabrication of Ga2O3-sensing material developed so far. Then, we will concentrate our discussion on the state-of-the-art Ga2O3-based gas sensor devices and put an emphasis on seven sophisticated strategies to improve their gas-sensing performance in terms of material engineering and device optimization. Finally, we give some concluding remarks and put forward some suggestions, including (i) construction of hybrid structures with two-dimensional materials and organic polymers, (ii) combination with density functional theoretical calculations and machine learning, and (iii) development of optical sensors using the characteristic optical spectra for the future development of novel Ga2O3-based gas sensors. Full article
(This article belongs to the Special Issue Development of Novel Functional Materials for the Manufacture of Electronic and Optoelectronic Devices)
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22 pages, 6169 KiB  
Review
A Review of Magnetic Flux Leakage Nondestructive Testing
by Bo Feng, Jianbo Wu, Hongming Tu, Jian Tang and Yihua Kang
Materials 2022, 15(20), 7362; https://doi.org/10.3390/ma15207362 - 20 Oct 2022
Cited by 65 | Viewed by 9149
Abstract
Magnetic flux leakage (MFL) testing is a widely used nondestructive testing (NDT) method for the inspection of ferromagnetic materials. This review paper presents the basic principles of MFL testing and summarizes the recent advances in MFL. An analytical expression for the leakage magnetic [...] Read more.
Magnetic flux leakage (MFL) testing is a widely used nondestructive testing (NDT) method for the inspection of ferromagnetic materials. This review paper presents the basic principles of MFL testing and summarizes the recent advances in MFL. An analytical expression for the leakage magnetic field based on the 3D magnetic dipole model is provided. Based on the model, the effects of defect size, defect orientation, and liftoff distance have been analyzed. Other influencing factors, such as magnetization strength, testing speed, surface roughness, and stress, have also been introduced. As the most important steps of MFL, the excitation method (a permanent magnet, DC, AC, pulsed) and sensing methods (Hall element, GMR, TMR, etc.), have been introduced in detail. Finally, the algorithms for the quantification of defects and the applications of MFL have been introduced. Full article
(This article belongs to the Special Issue Electromagnetic Nondestructive Testing)
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19 pages, 2664 KiB  
Article
Performance of Capsules in Self-Healing Cementitious Material
by Mouna A. Reda and Samir E. Chidiac
Materials 2022, 15(20), 7302; https://doi.org/10.3390/ma15207302 - 19 Oct 2022
Cited by 11 | Viewed by 2995
Abstract
Encapsulation is a very promising technique that is being explored to enhance the autonomous self-healing of cementitious materials. However, its success requires the survival of self-healing capsules during mixing and placing conditions, while still trigger the release of a healing agent upon concrete [...] Read more.
Encapsulation is a very promising technique that is being explored to enhance the autonomous self-healing of cementitious materials. However, its success requires the survival of self-healing capsules during mixing and placing conditions, while still trigger the release of a healing agent upon concrete cracking. A review of the literature revealed discontinuities and inconsistencies in the design and performance evaluation of self-healing cementitious material. A finite element model was developed to study the compatibility requirements for the capsule and the cementing material properties while the cement undergoes volume change due to hydration and/or drying. The FE results have provided insights into the observed inconsistencies and the importance of having capsules’ mechanical and geometrical properties compatible with the cementitious matrix. Full article
(This article belongs to the Special Issue Self-Healing Cementitious Material System)
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10 pages, 4878 KiB  
Article
Versatile Medium Entropy Ti-Based Bulk Metallic Glass Composites
by Tianzeng Liu, Yanchun Zhao, Li Feng and Pan Gong
Materials 2022, 15(20), 7304; https://doi.org/10.3390/ma15207304 - 19 Oct 2022
Cited by 1 | Viewed by 1658
Abstract
An ultra-strong Ti-based bulk metallic glass composite was developed via the transformation-induced plasticity (TRIP) effect to enhance both the ductility and work-hardening capability of the amorphous matrix. The functionally graded composites with a continuous gradient microstructure were obtained. It was found that the [...] Read more.
An ultra-strong Ti-based bulk metallic glass composite was developed via the transformation-induced plasticity (TRIP) effect to enhance both the ductility and work-hardening capability of the amorphous matrix. The functionally graded composites with a continuous gradient microstructure were obtained. It was found that the austenitic center possesses good plasticity and toughness. Furthermore, the amorphous surface exhibited high strength and hardness, as well as excellent wear corrosion resistance. Compared with the Ti-6Al-4V alloy, bulk metallic glass composites (BMGCs) exhibit better spontaneous passivation behavior during the potential dynamic polarization. No crystallization was observed on the friction surface, indicating their good friction-reduction and anti-wear properties. Full article
(This article belongs to the Special Issue Physical Metallurgy of Metals and Alloys)
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20 pages, 4900 KiB  
Article
Bio-Activation of HA/β-TCP Porous Scaffolds by High-Pressure CO2 Surface Remodeling: A Novel “Coating-from” Approach
by Clémentine Aubry, Christophe Drouet, Thierry Azaïs, Hyoung-Jun Kim, Jae-Min Oh, Ipek Karacan, Joshua Chou, Besim Ben-Nissan, Séverine Camy and Sophie Cazalbou
Materials 2022, 15(20), 7306; https://doi.org/10.3390/ma15207306 - 19 Oct 2022
Cited by 1 | Viewed by 2651
Abstract
Biphasic macroporous Hydroxyapatite/β-Tricalcium Phosphate (HA/β-TCP) scaffolds (BCPs) are widely used for bone repair. However, the high-temperature HA and β-TCP phases exhibit limited bioactivity (low solubility of HA, restricted surface area, low ion release). Strategies were developed to coat such BCPs with biomimetic apatite [...] Read more.
Biphasic macroporous Hydroxyapatite/β-Tricalcium Phosphate (HA/β-TCP) scaffolds (BCPs) are widely used for bone repair. However, the high-temperature HA and β-TCP phases exhibit limited bioactivity (low solubility of HA, restricted surface area, low ion release). Strategies were developed to coat such BCPs with biomimetic apatite to enhance bioactivity. However, this can be associated with poor adhesion, and metastable solutions may prove difficult to handle at the industrial scale. Alternative strategies are thus desirable to generate a highly bioactive surface on commercial BCPs. In this work, we developed an innovative “coating from” approach for BCP surface remodeling via hydrothermal treatment under supercritical CO2, used as a reversible pH modifier and with industrial scalability. Based on a set of complementary tools including FEG-SEM, solid state NMR and ion exchange tests, we demonstrate the remodeling of macroporous BCP surface with the occurrence of dissolution–reprecipitation phenomena involving biomimetic CaP phases. The newly precipitated compounds are identified as bone-like nanocrystalline apatite and octacalcium phosphate (OCP), both known for their high bioactivity character, favoring bone healing. We also explored the effects of key process parameters, and showed the possibility to dope the remodeled BCPs with antibacterial Cu2+ ions to convey additional functionality to the scaffolds, which was confirmed by in vitro tests. This new process could enhance the bioactivity of commercial BCP scaffolds via a simple and biocompatible approach. Full article
(This article belongs to the Special Issue Bio-Inspired and Biomimetic Materials for Healthcare: From Nature to Clinics)
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10 pages, 2602 KiB  
Article
Characterization of Porous CuO Films for H2S Gas Sensors
by Dawoon Jung, Sehoon Hwang, Hyun-Jong Kim, Jae-Hee Han and Ho-Nyun Lee
Materials 2022, 15(20), 7270; https://doi.org/10.3390/ma15207270 - 18 Oct 2022
Cited by 11 | Viewed by 2400
Abstract
Using a thermal evaporator, various porous Cu films were deposited according to the deposition pressure. CuO films were formed by post heat treatment in the air. Changes in morphological and structural characteristics of films were analyzed using field-emission scanning electron microscopy (FE-SEM) and [...] Read more.
Using a thermal evaporator, various porous Cu films were deposited according to the deposition pressure. CuO films were formed by post heat treatment in the air. Changes in morphological and structural characteristics of films were analyzed using field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Relative density and porosity were quantitatively calculated. CuO films with various pores ranging from 39.4 to 95.2% were successfully manufactured and were applied as gas sensors for H2S detection on interdigitated electrode (IDE) substrate. Resistance change was monitored at 325 °C and an increase in porosity of the film improved the sensor performance. The CuO-10 gas sensor with a high porosity of 95.2% showed a relatively high response (2.7) and a fast recovery time (514 s) for H2S 1.5 ppm. It is confirmed that the porosity of the CuO detection layer had a significant effect on response and recovery time. Full article
(This article belongs to the Special Issue Preparation, Characterization and Application of Metal Oxide Thin Films)
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25 pages, 3871 KiB  
Review
Structural Changes in Metallic Glass-Forming Liquids on Cooling and Subsequent Vitrification in Relationship with Their Properties
by D. V. Louzguine-Luzgin
Materials 2022, 15(20), 7285; https://doi.org/10.3390/ma15207285 - 18 Oct 2022
Cited by 27 | Viewed by 4064
Abstract
The present review is related to the studies of structural changes observed in metallic glass-forming liquids on cooling and subsequent vitrification in terms of radial distribution function and its analogues. These structural changes are discussed in relationship with liquid’s properties, especially the relaxation [...] Read more.
The present review is related to the studies of structural changes observed in metallic glass-forming liquids on cooling and subsequent vitrification in terms of radial distribution function and its analogues. These structural changes are discussed in relationship with liquid’s properties, especially the relaxation time and viscosity. These changes are found to be directly responsible for liquid fragility: deviation of the temperature dependence of viscosity of a supercooled liquid from the Arrhenius equation through modification of the activation energy for viscous flow. Further studies of this phenomenon are necessary to provide direct mathematical correlation between the atomic structure and properties. Full article
(This article belongs to the Special Issue Glass Science and First-Order Transitions at a Turning Point)
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14 pages, 2095 KiB  
Article
Multifunctional Microspheres Based on D-Mannose and Resveratrol for Ciprofloxacin Release
by Roberta Cassano, Federica Curcio, Debora Procopio, Marco Fiorillo and Sonia Trombino
Materials 2022, 15(20), 7293; https://doi.org/10.3390/ma15207293 - 18 Oct 2022
Cited by 5 | Viewed by 2497
Abstract
This article describes the preparation, characterization, and performance evaluation of functional microspheres useful for the release of ciprofloxacin. The particles were obtained using D-mannose, a natural aldohexose sugar, and resveratrol, a powerful antioxidant. In particular, the above compounds were initially converted into D-mannose [...] Read more.
This article describes the preparation, characterization, and performance evaluation of functional microspheres useful for the release of ciprofloxacin. The particles were obtained using D-mannose, a natural aldohexose sugar, and resveratrol, a powerful antioxidant. In particular, the above compounds were initially converted into D-mannose carboxylate and resveratrol methacrylate and, therefore, subjected to an esterification reaction. The resulting product was used for the preparation of the microspheres which were characterized by light scattering, FT-IR spectrophotometry and scanning electron microscopy (SEM). Subsequently, their degree of bloating was evaluated at pH 1.2 to simulate the pH of the stomach, at pH 6.8 and pH 7.4 to mimic the intestinal environment. The antibiotic ciprofloxacin was then loaded into the microspheres, with an encapsulation efficiency of 100%. The cumulative amount of drug released was 55% at pH 6.8 and 99% at pH 7.4. The tests conducted to evaluate the antibacterial activity demonstrated the ability of the microspheres obtained to inhibit the growth of Escherichia coli. The antioxidant efficacy, due to the presence of resveratrol in their structure, was confirmed using rat liver microsomal membranes. The results obtained have highlighted how the microspheres based on D-mannose and resveratrol can be considered promising multifunctional vectors useful in the treatment of intestinal and urinary infections. Full article
(This article belongs to the Special Issue Drug Delivery: Recent Developments and Future Prospects)
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10 pages, 1990 KiB  
Communication
The Research on Anti-Nickel Contamination Mechanism and Performance for Boron-Modified FCC Catalyst
by Chengyuan Yuan, Lei Zhou, Qiang Chen, Chengzhuang Su, Zhongfu Li and Guannan Ju
Materials 2022, 15(20), 7220; https://doi.org/10.3390/ma15207220 - 17 Oct 2022
Cited by 6 | Viewed by 1690
Abstract
Fluid catalytic cracking (FCC) is still a key process in the modern refining area, in which nickel-contamination for an FCC catalyst could obviously increase the dry gas and coke yields and thus seriously affect the stability of the FCC unit. From the points [...] Read more.
Fluid catalytic cracking (FCC) is still a key process in the modern refining area, in which nickel-contamination for an FCC catalyst could obviously increase the dry gas and coke yields and thus seriously affect the stability of the FCC unit. From the points of surface acidity modification and Ni-passivation, in this paper, a boron-modified FCC catalyst (BM-Cat) was prepared using the in situ addition method with B2O3 as a boron source and emphatically investigated its mechanism and performance of anti-nickel contamination. The mechanism research results suggested that, in calcination, boron could destroy the structure of the Y zeolite and thus decrease the total acid sites and strong acid sites of the Y zeolite from 291.5 and 44.6 μmol·g−1 to 244.2 and 32.1 μmol·g−1, respectively, which could obviously improve the dry gas and coke selectivity of the catalyst and thus enhance the nickel capacity for BM-Cat; on the other hand, under hydrothermal conditions, boron could react with NiO and form into NiB2O4, which could obviously raise the range of the reduction temperature for NiO from 350–600 °C to 650–800 °C and thus promote the nickel-passivation ability for BM-Cat. Therefore, evaluation results of heavy oil catalytic cracking indicated that, under the same nickel-contamination condition, in contrast to the compared catalyst (C-Cat), the dry gas yield, coke yield, and H2/CH4 of BM-Cat obviously decreased by 0.77 percentage points, 2.09 percentage points, and 13.53%, respectively, with light yield and total liquid yield increasing by 3.25 and 2.08 percentage points, respectively, which fully demonstrates the excellent anti-nickel contamination performance of BM-Cat. Full article
(This article belongs to the Section Catalytic Materials)
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21 pages, 7475 KiB  
Article
Entalpy of Mixing, Microstructure, Structural, Thermomagnetic and Mechanical Properties of Binary Gd-Pb Alloys
by Piotr Gębara, Mariusz Hasiak, Jozef Kovac and Michal Rajnak
Materials 2022, 15(20), 7213; https://doi.org/10.3390/ma15207213 - 16 Oct 2022
Viewed by 1636
Abstract
The aim of the present work is to study the phase composition, microstructure and magnetocaloric effect of binary Gd100−xPbx (where x = 5, 10, 15 and 20) alloys. The XRD and SEM/EDX analysis confirmed a biphasic structure built by Gd(Pb) [...] Read more.
The aim of the present work is to study the phase composition, microstructure and magnetocaloric effect of binary Gd100−xPbx (where x = 5, 10, 15 and 20) alloys. The XRD and SEM/EDX analysis confirmed a biphasic structure built by Gd(Pb) and Gd5Pb3 phases. The analysis of M vs. T curves showed the evolution of the Curie point of recognized phases. The temperature dependences of magnetic entropy change revealed two maxima corresponding to the recognized phases. The analysis of the exponent n (ΔSMmax = C(Bmax)n) confirmed the multiphase composition of the produced alloys. The same behavior was also observed in investigations of mechanical properties. Full article
(This article belongs to the Special Issue Structure, Magnetocaloric Properties, and Thermodynamic Modeling of Alloys)
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15 pages, 4963 KiB  
Article
Effects of Operating Conditions and Pit Area Ratio on the Coefficient of Friction of Textured Assemblies in Lubricated Reciprocating Sliding
by Slawomir Wos, Waldemar Koszela, Andrzej Dzierwa and Pawel Pawlus
Materials 2022, 15(20), 7199; https://doi.org/10.3390/ma15207199 - 15 Oct 2022
Cited by 6 | Viewed by 1668
Abstract
The experiment was carried out in a reciprocating lubricated conformal sliding contact between steel discs of the same hardness. The effects of disc surface texturing on the friction coefficient at various operating conditions (temperature, normal load, and frequency of oscillations) were studied. Under [...] Read more.
The experiment was carried out in a reciprocating lubricated conformal sliding contact between steel discs of the same hardness. The effects of disc surface texturing on the friction coefficient at various operating conditions (temperature, normal load, and frequency of oscillations) were studied. Under various conditions, surface texturing caused friction reductions of sliding pairs. The largest reduction was 4.6 times at a lower temperature and 2.5 times at a higher temperature. The effect of the pit area ratio on the friction reduction was visible at a higher temperature. The highest dimple density of 25% corresponded to a lower coefficient of friction than the smallest density of 9%. The sliding pair with a dimple density of 17% led to large variation of the friction force. At lower temperatures, the coefficients of friction were lower compared to tests at higher temperatures. Full article
(This article belongs to the Special Issue Tribology: Friction and Wear of Engineering Materials (Second Volume))
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21 pages, 4993 KiB  
Article
On As(III) Adsorption Characteristics of Innovative Magnetite Graphene Oxide Chitosan Microsphere
by Huimei Shan, Yunquan Liu, Chunya Zeng, Sanxi Peng and Hongbin Zhan
Materials 2022, 15(20), 7156; https://doi.org/10.3390/ma15207156 - 14 Oct 2022
Cited by 12 | Viewed by 1896
Abstract
A magnetite graphene oxide chitosan (MGOCS) composite microsphere was specifically prepared to efficiently adsorb As(III) from aqueous solutions. The characterization analysis of BET, XRD, VSM, TG, FTIR, XPS, and SEM-EDS was used to identify the characteristics and adsorption mechanism. Batch experiments were carried [...] Read more.
A magnetite graphene oxide chitosan (MGOCS) composite microsphere was specifically prepared to efficiently adsorb As(III) from aqueous solutions. The characterization analysis of BET, XRD, VSM, TG, FTIR, XPS, and SEM-EDS was used to identify the characteristics and adsorption mechanism. Batch experiments were carried out to determine the effects of the operational parameters and to evaluate the adsorption kinetic and equilibrium isotherm. The results show that the MGOCS composite microsphere with a particle size of about 1.5 mm can be prepared by a straightforward method of dropping FeCl2, graphene oxide (GO), and chitosan (CS) mixtures into NaOH solutions and then drying the mixed solutions at 45 °C. The produced MGOCS had a strong thermal stability with a mass loss of <30% below 620 °C. The specific surface area and saturation magnetization of the produced MGOCS was 66.85 m2/g and 24.35 emu/g, respectively. The As(III) adsorption capacity (Qe) and removal efficiency (Re) was only 0.25 mg/g and 5.81% for GOCS, respectively. After 0.08 mol of Fe3O4 modification, more than 53% of As(III) was efficiently removed by the formed MGOCS from aqueous solutions over a wide pH range of 5–10, and this was almost unaffected by temperature. The coexisting ion of PO43− decreased Qe from 3.81 mg/g to 1.32 mg/g, but Mn2+ increased Qe from 3.50 mg/g to 4.19 mg/g. The As(III) adsorption fitted the best to the pseudo-second-order kinetic model, and the maximum Qe was 20.72 mg/g as fitted by the Sips model. After four times regeneration, the Re value of As(III) slightly decreased from 76.2% to 73.8%, and no secondary pollution of Fe happened. Chemisorption is the major mechanism for As(III) adsorption, and As(III) was adsorbed on the surface and interior of the MGOCS, while the adsorbed As(III) was partially oxidized to As(V) accompanied by the reduction of Fe(III) to Fe(II). The produced As(V) was further adsorbed through ligand exchange (by forming Fe–O–As complexes) and electrostatic attraction, enhancing the As(III) removal. As an easily prepared and environmental-friendly composite, MGOCS not only greatly adsorbs As(III) but also effectively removes Cr(VI) and As(V) (Re > 60%) and other metals, showing a great advantage in the treatment of heavy metal-contaminated water. Full article
(This article belongs to the Section Biomaterials)
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15 pages, 5050 KiB  
Article
Comparison Study of PVD Coatings: TiN/AlTiN, TiN and TiAlSiN Used in Wood Machining
by Beata Kucharska, Paweł Czarniak, Krzysztof Kulikowski, Agnieszka Krawczyńska, Krzysztof Rożniatowski, Jerzy Kubacki, Karol Szymanowski, Peter Panjan and Jerzy Robert Sobiecki
Materials 2022, 15(20), 7159; https://doi.org/10.3390/ma15207159 - 14 Oct 2022
Cited by 16 | Viewed by 3365
Abstract
In this paper, we analyze the possibilities of the protection of tools for wood machining with PVD (Physical Vapor Deposition) hard coatings. The nanolayered TiN/AlTiN coating, nanocomposite TiAlSiN coatings, and single layer TiN coating were analyzed in order to use them for protection [...] Read more.
In this paper, we analyze the possibilities of the protection of tools for wood machining with PVD (Physical Vapor Deposition) hard coatings. The nanolayered TiN/AlTiN coating, nanocomposite TiAlSiN coatings, and single layer TiN coating were analyzed in order to use them for protection of tools for wood machining. Both nanostructured coatings were deposited in an industrial magnetron sputtering system on the cutting blades made of sintered carbide WC-Co, while TiN single layer coating was deposited by evaporation using thermionic arc. In the case of TiN/AlTiN nanolayer coatings the thickness of the individual TiN and AlTiN layer was in the 5–10 nm range, depending on the substrate vertical position. The microstructure and chemical composition of coatings were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) method. Additionally, in the case of the TiN/AlTiN coating, which was characterized by the best durability characteristics, the transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) methods were applied. The coatings adhesion to the substrate was analyzed by scratch test method combined with optical microscopy. Nano-hardness and durability tests were performed with uncoated and coated blades using chipboard. The best results durability characteristics were observed for TiN/AlTiN nanolayered coating. Performance tests of knives protected with TiN and TiAlSiN hard coatings did not show significantly better results compared to uncoated ones. Full article
(This article belongs to the Special Issue Advanced Materials – Microstructure, Manufacturing and Analysis)
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22 pages, 10702 KiB  
Article
Development and Characterisation of Joints with Novel Densified and Wood/Cork Composite Substrates
by Luis M. R. M. Corte-Real, Shahin Jalali, Catarina S. P. Borges, Eduardo A. S. Marques, Ricardo J. C. Carbas and Lucas F. M. da Silva
Materials 2022, 15(20), 7163; https://doi.org/10.3390/ma15207163 - 14 Oct 2022
Cited by 3 | Viewed by 2078
Abstract
The automotive industry, driven by the desire to decrease the environmental impact of vehicles, is permanently seeking to develop lightweight structural components, which lead to lower gas emissions and energy consumption, reducing their carbon footprint. In parallel, adopting innovative, constructive solutions, which dispense [...] Read more.
The automotive industry, driven by the desire to decrease the environmental impact of vehicles, is permanently seeking to develop lightweight structural components, which lead to lower gas emissions and energy consumption, reducing their carbon footprint. In parallel, adopting innovative, constructive solutions, which dispense non-recyclable and energy-intensive materials, can increase the footprint reduction. Thus, an increase in the use of renewable materials for structural applications, including wood and its by-products, has been observed over the last few decades. Furthermore, composite materials are often joined by using petroleum-based synthetic adhesives, which should be progressively replaced by eco-friendly bio-adhesives. In this study, novel densified wood and wood/cork composites, joined with a bio-adhesive, are proposed and characterised. The densification of the wood aims to enhance the mechanical properties of the natural material, with the purpose of improving the energy absorption of the wood/bio-adhesive joint. To mitigate delamination and the brittle behaviour of wood/cork agglomerates were introduced between the wood substrate and the bio-adhesive. Different configurations of single lap joints (SLJ) were manufactured to study the effect of the overlap length and loading rate on the performance of the joints, both in terms of failure load and energy absorption. Afterward, the joints were numerically simulated. The densification process was successful, although it represents an additional challenge in terms of surface flatness, because the bio-adhesive requires zero bondline thickness. The increase of the overlap had a positive impact on the energy absorption of the joint, and the addition of cork resulted in a more consistent failure mode and higher strain to failure. The numerical models developed had a good correlation with the experimental results. Full article
(This article belongs to the Section Biomaterials)
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19 pages, 11074 KiB  
Article
Electronic Band Structure and Surface States in Dirac Semimetal LaAgSb2
by Marcin Rosmus, Natalia Olszowska, Zbigniew Bukowski, Paweł Starowicz, Przemysław Piekarz and Andrzej Ptok
Materials 2022, 15(20), 7168; https://doi.org/10.3390/ma15207168 - 14 Oct 2022
Cited by 10 | Viewed by 3512
Abstract
LaAgSb2 is a Dirac semimetal showing charge density wave (CDW) order. Previous angle-resolved photoemission spectroscopy (ARPES) results suggest the existence of the Dirac-cone-like structure in the vicinity of the Fermi level along the Γ–M direction. This paper is devoted to a [...] Read more.
LaAgSb2 is a Dirac semimetal showing charge density wave (CDW) order. Previous angle-resolved photoemission spectroscopy (ARPES) results suggest the existence of the Dirac-cone-like structure in the vicinity of the Fermi level along the Γ–M direction. This paper is devoted to a complex analysis of the electronic band structure of LaAgSb2 by means of ARPES and theoretical studies within the ab initio method as well as tight binding model formulation. To investigate the possible surface states, we performed the direct DFT slab calculation and the surface Green function calculation for the (001) surface. The appearance of the surface states, which depends strongly on the surface, points to the conclusion that LaSb termination is realized in the cleaved crystals. Moreover, the surface states predicted by our calculations at the Γ and X points are found by ARPES. Nodal lines, which exist along the X–R and M–A paths due to crystal symmetry, are also observed experimentally. The calculations reveal other nodal lines, which originate from the vanishing of spin–orbit splitting and are located at the X–M–A–R plane at the Brillouin zone boundary. In addition, we analyze the band structure along the Γ–M path to verify whether Dirac surface states can be expected. Their appearance in this region is not confirmed. Full article
(This article belongs to the Special Issue Advances in Crystal Material: Design, Characterization, and Applications)
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15 pages, 4192 KiB  
Article
Improved Enamel Acid Resistance Using Biocompatible Nano-Hydroxyapatite Coating Method
by Ryouichi Satou, Miyu Iwasaki, Hideyuki Kamijo and Naoki Sugihara
Materials 2022, 15(20), 7171; https://doi.org/10.3390/ma15207171 - 14 Oct 2022
Cited by 4 | Viewed by 2597
Abstract
In this study, we attempted to develop a dental caries prevention method using a bioapatite (BioHap), an eggshell-derived apatite with nanoparticle size and biocompatibility, with a high-concentration fluoride tooth surface application method. The enamel acid resistance after the application of the proposed method [...] Read more.
In this study, we attempted to develop a dental caries prevention method using a bioapatite (BioHap), an eggshell-derived apatite with nanoparticle size and biocompatibility, with a high-concentration fluoride tooth surface application method. The enamel acid resistance after the application of the proposed method was compared with that of a conventional topical application of fluoride using bovine tooth enamel as an example. The tooth samples were divided into three groups based on the preventive treatment applied, and an acid challenge was performed. The samples were evaluated for acid resistance using qualitative and quantitative analytical methods. The BioHap group demonstrated reduced enamel loss and improved micro-Vickers hardness, along with a thick coating layer, decreased reaction area depth, and decreased mineral loss value and lesion depth. The combination of BioHap with high-concentration fluoride led to the formation of a thick coating layer on the enamel surface and better suppression of demineralization than the conventional method, both qualitatively and quantitatively. The proposed biocompatible nano-hydroxyapatite coating method is expected to become a new standard for providing professional care to prevent dental caries. Full article
(This article belongs to the Special Issue Materials for Hard Tissue Repair and Regeneration (Second Volume))
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14 pages, 4776 KiB  
Article
Experimental Investigation on the Use of a PEI Foam as Core Material for the In-Situ Production of Thermoplastic Sandwich Structures Using Laser-Based Thermoplastic Automated Fiber Placement
by Berend Denkena, Carsten Schmidt, Christopher Schmitt and Maximilian Kaczemirzk
Materials 2022, 15(20), 7141; https://doi.org/10.3390/ma15207141 - 13 Oct 2022
Cited by 2 | Viewed by 2598
Abstract
Laser-based thermoplastic automated fiber placement (TAFP) is nowadays mainly used to produce pure carbon fiber-reinforced plastic (CFRP) structures. This paper investigates the feasibility of a novel application: The deposition of thermoplastic prepreg tapes onto a thermoplastic foam for the production of thermoplastic sandwich [...] Read more.
Laser-based thermoplastic automated fiber placement (TAFP) is nowadays mainly used to produce pure carbon fiber-reinforced plastic (CFRP) structures. This paper investigates the feasibility of a novel application: The deposition of thermoplastic prepreg tapes onto a thermoplastic foam for the production of thermoplastic sandwich structures. Therefore, simple deposition experiments of thermoplastic PEEK/CF prepreg tapes on a PEI closed-cell foam were carried out. 3D surface profile measurements and peel tests according to DIN EN 28510-1 standard were used to investigate the joining area and bonding quality. The results show that a cohesive bond is formed between the deposited tapes and the foam core, however the foam structure in the area of the deposited tapes deforms in dependence of the process parameters, and increasingly with higher deposition temperatures. Due to the deformations that occur during tape deposition, the thermomechanical foam behavior under the TAFP process conditions was investigated in more detail in a subsequent study for an extensive parameter space using a simple experimental setup. Results show that for suitable process parameters, namely a short contact time and a high temperature, the foam deformation can be minimized with the simultaneous formation of a thin melting layer required for cohesive bonding. The inner foam core structure remains unaffected. Full article
(This article belongs to the Special Issue Sandwich Composites: Design, Simulation and Applications)
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20 pages, 4546 KiB  
Article
Programmable Density of Laser Additive Manufactured Parts by Considering an Inverse Problem
by Mika León Altmann, Stefan Bosse, Christian Werner, Rainer Fechte-Heinen and Anastasiya Toenjes
Materials 2022, 15(20), 7090; https://doi.org/10.3390/ma15207090 - 12 Oct 2022
Cited by 1 | Viewed by 2440
Abstract
In this Article, the targeted adjustment of the relative density of laser additive manufactured components made of AlSi10Mg is considered. The interest in demand-oriented process parameters is steadily increasing. Thus, shorter process times and lower unit costs can be achieved with decreasing component [...] Read more.
In this Article, the targeted adjustment of the relative density of laser additive manufactured components made of AlSi10Mg is considered. The interest in demand-oriented process parameters is steadily increasing. Thus, shorter process times and lower unit costs can be achieved with decreasing component densities. Especially when hot isostatic pressing is considered as a post-processing step. In order to be able to generate process parameters automatically, a model hypothesis is learned via artificial neural networks (ANN) for a density range from 70% to almost 100%, based on a synthetic dataset with equally distributed process parameters and a statistical test series with 256 full factorial combined instances. This allows the achievable relative density to be predicted from given process parameters. Based on the best model, a database approach and supervised training of concatenated ANNs are developed to solve the inverse parameter prediction problem for a target density. In this way, it is possible to generate a parameter prediction model for the high-dimensional result space through constraints that are shown with synthetic test data sets. The presented concatenated ANN model is able to reproduce the origin distribution. The relative density of synthetic data can be predicted with an R2-value of 0.98. The mean build rate can be increased by 12% with the formulation of a hint during the backward model training. The application of the experimental data shows increased fuzziness related to the big data gaps and a small number of instances. For practical use, this algorithm could be trained on increased data sets and can be expanded by properties such as surface quality, residual stress, or mechanical strength. With knowledge of the necessary (mechanical) properties of the components, the model can be used to generate appropriate process parameters. This way, the processing time and the amount of scrap parts can be reduced. Full article
(This article belongs to the Special Issue Recent Advances in Metal Powder Based Additive Manufacturing)
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16 pages, 5351 KiB  
Article
Sliding Friction and Wear Characteristics of Wire Rope Contact with Sheave under Long-Distance Transmission Conditions
by Xiangdong Chang, Yuxing Peng, Zhencai Zhu, Hao Lu, Wei Tang and Xing Zhang
Materials 2022, 15(20), 7092; https://doi.org/10.3390/ma15207092 - 12 Oct 2022
Cited by 4 | Viewed by 4311
Abstract
Wire rope has different degrees of surface wear under long-distance transmission conditions, which leads to performance degradation and greatly threatens its safety and reliability in service. In this paper, friction and wear tests between the transmission wire rope and sheave under different sliding [...] Read more.
Wire rope has different degrees of surface wear under long-distance transmission conditions, which leads to performance degradation and greatly threatens its safety and reliability in service. In this paper, friction and wear tests between the transmission wire rope and sheave under different sliding velocities (from 0.8 m/s to 1.6 m/s) were carried out using a homemade test rig. The material of the steel wires was low carbon steel, and pulley material was ASTM A36 steel plate. The sliding friction coefficient (COF), friction temperature rise, wear characteristic parameters and wear mechanisms of the wire rope were analyzed. Additionally, the effect of different wear on the fracture behavior of the wire rope was investigated by a breaking tensile test. The results show that the average COF in the relatively stable stage decreased from approximately 0.58 to 0.51 with the increase of sliding velocity. The temperature rise of the wire rope increased rapidly with an increase of sliding velocity, from approximately 52.7 °C to 116.2 °C. The maximum wear width was the smallest when the sliding velocity was 1.2 m/s (approximately 1.5 mm). The surface wear was characterized by spalling, furrowing and plastic deformation, which are strongly affected by the sliding velocity. The wear mechanisms of the wire rope were mainly adhesive wear and abrasive wear. Surface wear changes the fracture morphology of the wire rope and accelerates its fracture speed. Full article
(This article belongs to the Special Issue Tribology: Friction and Wear of Engineering Materials (Second Volume))
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16 pages, 4061 KiB  
Article
Influence of Heat Treatment on Microstructure and Mechanical Properties of AZ61 Magnesium Alloy Prepared by Selective Laser Melting (SLM)
by Shuai Liu and Hanjie Guo
Materials 2022, 15(20), 7067; https://doi.org/10.3390/ma15207067 - 11 Oct 2022
Cited by 14 | Viewed by 2382
Abstract
From previous studies, it is known that the dissolution of β-Mg17Al12 at high temperature and the increase of densities at high pressure after hot isostatic pressing (HIP) are the two main reasons for significant improvement in the ductility of AZ61 [...] Read more.
From previous studies, it is known that the dissolution of β-Mg17Al12 at high temperature and the increase of densities at high pressure after hot isostatic pressing (HIP) are the two main reasons for significant improvement in the ductility of AZ61 magnesium alloy prepared by SLM. However, the mechanism of dissolution of β-Mg17Al12 in SLMed AZ61 magnesium alloy at high temperature is not clear. To illustrate the mechanism of the effect of β-Mg17Al12 dissolution on the ductility of SLMed AZ61 Mg alloy, the effect of solid solution heat treatment (T4) on the microstructure and mechanical properties of SLMed AZ61 was investigated and the kinetic model of β-Mg17Al12 dissolution of SLMed AZ61 magnesium alloy was established. According to the results, there is no significant change in the dissolution of the β-Mg17Al12 with an increase of temperature and time when the T4 temperature is lower than 410 °C. At the optimum solution heat treatment temperature of 410 °C, the dissolution rate is accelerated and the β-Mg17Al12 is completely dissolved after 2 h. In addition, the dissolution rate of β-Mg17Al12 decreases with the increase of dissolution time. The strength of SLMed AZ61 magnesium alloy decreases and the ductility increases as the T4 temperature increases. The strength of the specimens is reduced by grain coarsening (29.2 ± 3.7 μm), but the elongation is increased by 90% compared to SLMed AZ61, due to the effect of β-Mg17Al12 dissolution. Full article
(This article belongs to the Special Issue Additive Manufacturing (AM) of Metal Alloys: Microstructure and Mechanical Performance)
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18 pages, 11098 KiB  
Article
Exceptional Strengthening Efficiency and Hardness of Ti/Mg-9Al-Zn-0.3Mn Matrix Composite
by Rongrong Wang, Yejin Han, Huan Yu, Qian Su, Hang Li, Kaiming Cheng, Jixue Zhou, Shouqiu Tang and Wei Ju
Materials 2022, 15(20), 7075; https://doi.org/10.3390/ma15207075 - 11 Oct 2022
Cited by 9 | Viewed by 1775
Abstract
The involvement of magnesium matrix composite enhanced by metal particles, the development of low lattice mismatch interface, and the refining of particle size are all of great significance in improving strengthening efficiency. In this work, nano-crystalline Ti/Mg-9Al-Zn-0.3Mn composites were prepared by mechanical milling. [...] Read more.
The involvement of magnesium matrix composite enhanced by metal particles, the development of low lattice mismatch interface, and the refining of particle size are all of great significance in improving strengthening efficiency. In this work, nano-crystalline Ti/Mg-9Al-Zn-0.3Mn composites were prepared by mechanical milling. The microstructure was characterized and the mechanical property was measured. After mechanical milling, the grain of the Mg matrix was refined to ~72 nm. Ti particles were smashed to submicron scale, and dispersed in the Mg matrix. In total, 68% of Ti particles were nano-scale and the average particle size was 133 nm. A nano-scale Mg17Al12 precipitate was found and the average particle size was approximately 44 nm. Meanwhile, coherent interfaces of Ti/Mg and Mg17Al12/Mg were observed, and it was found that the (101)Mg plane and (100)Ti plane inclined 12° and [044]Mg17Al12 was parallel to [010]Mg. The hardness of the milled Ti/Mg-9Al-Zn-0.3Mn composite was 1.98 GPa, 247% higher than the initial alloy. Milled Mg-9Al-Zn-0.3Mn alloy under the same preparation processing was used as a comparison, and the value of hardness was 1.53 GPa. Tiny Ti particles displayed excellent strengthening efficiency. Strengthening mechanisms of the milled Ti/Mg-9Al-Zn-0.3Mn composite were analyzed and the main strengthening mechanisms included the strengthening of grain boundary strengthening, Orowan strengthening, dislocation strengthening, solid solution strengthening and load-bearing strengthening, which accounted for 56.3%, 18.2%, 17.4%, 4.7% and 3.5%, respectively. Full article
(This article belongs to the Section Advanced Materials Characterization)
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29 pages, 81231 KiB  
Review
A Review of the Intelligent Optimization and Decision in Plastic Forming
by Xuefeng Tang, Zhizhou Wang, Lei Deng, Xinyun Wang, Jinchuan Long, Xin Jiang, Junsong Jin and Juchen Xia
Materials 2022, 15(19), 7019; https://doi.org/10.3390/ma15197019 - 10 Oct 2022
Cited by 19 | Viewed by 4918
Abstract
The plastic forming process involves many influencing factors and has some inevitable disturbance factors, rendering the multi-objective collaborative optimization difficult. With the rapid development of big data and artificial intelligence (AI) technology, intelligent process optimization has become one of the critical technologies for [...] Read more.
The plastic forming process involves many influencing factors and has some inevitable disturbance factors, rendering the multi-objective collaborative optimization difficult. With the rapid development of big data and artificial intelligence (AI) technology, intelligent process optimization has become one of the critical technologies for plastic forming. This paper elaborated on the research progress on the intelligent optimization of plastic forming and the data-driven process planning and decision-making system in plastic forming process optimization. The development trend in intelligent optimization of the plastic forming process was researched. This review showed that the intelligent optimization algorithm has great potential in controlling forming quality, microstructure, and performance in plastic forming. It is a general trend to develop an intelligent optimization model of the plastic forming process with high integration, versatility, and high performance. Future research will take the data-driven expert system and digital twin system as the carrier, integrate the optimization algorithm and model, and realize the multi-scale, high-precision, high-efficiency, and real-time optimization of the plastic forming process. Full article
(This article belongs to the Special Issue Feature Papers in "Metals and Alloys" Section)
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16 pages, 4359 KiB  
Article
Nanoplatforms for Irinotecan Delivery Based on Mesoporous Silica Modified with a Natural Polysaccharide
by Ana-Maria Brezoiu, Ana-Maria Prelipcean, Daniel Lincu, Mihaela Deaconu, Eugeniu Vasile, Rodica Tatia, Ana-Maria Seciu-Grama, Cristian Matei and Daniela Berger
Materials 2022, 15(19), 7003; https://doi.org/10.3390/ma15197003 - 9 Oct 2022
Cited by 9 | Viewed by 2906
Abstract
Natural compounds are an important source of beneficial components that could be used in cancer therapy along with well-known cytostatic agents to enhance the therapeutic effect while targeting tumoral tissues. Therefore, nanoplatforms containing mesoporous silica and a natural polysaccharide, ulvan, extracted from Ulva [...] Read more.
Natural compounds are an important source of beneficial components that could be used in cancer therapy along with well-known cytostatic agents to enhance the therapeutic effect while targeting tumoral tissues. Therefore, nanoplatforms containing mesoporous silica and a natural polysaccharide, ulvan, extracted from Ulva Lactuca seaweed, were developed for irinotecan. Either mesoporous silica-ulvan nanoplatforms or irinotecan-loaded materials were structurally and morphologically characterized. In vitro drug release experiments in phosphate buffer solution with a pH of 7.6 emphasized the complete recovery of irinotecan in 8 h. Slower kinetics were obtained for the nanoplatforms with a higher amount of natural polysaccharide. Ulvan extract proved to be biocompatible up to 2 mg/mL on fibroblasts L929 cell line. The irinotecan-loaded nanoplatforms exhibited better anticancer activity than that of the drug alone on human colorectal adenocarcinoma cells (HT-29), reducing their viability to 60% after 24 h. Moreover, the cell cycle analysis proved that the irinotecan loading onto developed nanoplatforms caused an increase in the cell number trapped at G0/G1 phase and influenced the development of the tumoral cells. Full article
(This article belongs to the Special Issue Synthesis and Characterization of Nano-Biomaterials and Their Applications)
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21 pages, 3908 KiB  
Article
Experimental and Computational Studies on Bio-Inspired Flavylium Salts as Sensitizers for Dye-Sensitized Solar Cells
by Iulia Păușescu, Anamaria Todea, Diana-Maria Dreavă, Tania Boboescu, Bianca Pațcan, Larisa Pațcan, Daiana Albulescu, Valentin Badea, Francisc Peter, Róbert Tőtős, Daniel Ursu, Lorant Szolga and Mihai Medeleanu
Materials 2022, 15(19), 6985; https://doi.org/10.3390/ma15196985 - 8 Oct 2022
Cited by 5 | Viewed by 3465
Abstract
Six new bio-inspired flavylium salts were synthesized and investigated by a combined computational and experimental study for dye-sensitized solar cell applications. The compounds were characterized by FT–IR, UV–Vis, NMR spectroscopy, and LC–MS spectrometry techniques. The pH-dependent photochromic properties of the flavylium dyes were [...] Read more.
Six new bio-inspired flavylium salts were synthesized and investigated by a combined computational and experimental study for dye-sensitized solar cell applications. The compounds were characterized by FT–IR, UV–Vis, NMR spectroscopy, and LC–MS spectrometry techniques. The pH-dependent photochromic properties of the flavylium dyes were investigated through a UV–Vis spectroscopy study and revealed that they follow the same network of chemical reactions as anthocyanins upon pH changes. The structural and electronic properties of the dyes were investigated using density functional theory (DFT) and time-dependent density functional theory (TD–DFT). Geometry optimization calculation revealed that all dyes, regardless of the specie, flavylium cations or quinoidal bases, present a planar geometry. The photovoltaic performances of the dyes, in both flavylium and quinoidal base forms, were evaluated by the HOMO and LUMO energies and by calculating the light-harvesting efficiencies, the free energy change of electron injection, and the free energy change regeneration. The MO analysis showed that all dyes can inject electrons into the conduction band of the TiO2 upon excitation and that the redox couple can regenerate the oxidized dyes. The results obtained for the free energy change of electron injection suggest that the quinoidal bases should inject electrons into the semiconductor more efficiently than the flavylium cations. The values for the free energy change regeneration showed that the redox electrolyte can easily regenerate all dyes. Dipole moment analysis was also performed. DSSCs based on the dyes, in both flavylium and quinoidal base forms, were assembled, and their photovoltaic performances were evaluated by measuring the open-circuit voltage, the short circuit current density, the fill factor, and the energy conversion efficiency. Results obtained by both experimental and computational studies showed that the overall performances of the DSSCs with the quinoidal forms were better than those obtained with the flavylium cations dyes. Full article
(This article belongs to the Special Issue Soft Materials and Optical Devices)
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14 pages, 7651 KiB  
Article
The Microstructure and Strength of UFG 6060 Alloy after Superplastic Deformation at a Lower Homologous Temperature
by Elena V. Bobruk, Pavel D. Dolzhenko, Maxim Yu. Murashkin, Ruslan Z. Valiev and Nariman A. Enikeev
Materials 2022, 15(19), 6983; https://doi.org/10.3390/ma15196983 - 8 Oct 2022
Cited by 7 | Viewed by 2290
Abstract
The paper reports on the features of low-temperature superplasticity of the heat-treatable aluminum Al-Mg-Si alloy in the ultrafine-grained state at temperatures below 0.5 times the melting point as well as on its post-deformation microstructure and tensile strength. We show that the refined microstructure [...] Read more.
The paper reports on the features of low-temperature superplasticity of the heat-treatable aluminum Al-Mg-Si alloy in the ultrafine-grained state at temperatures below 0.5 times the melting point as well as on its post-deformation microstructure and tensile strength. We show that the refined microstructure is retained after superplastic deformation in the range of deformation temperatures of 120–180 °C and strain rates of 5 × 10–3 s–1–10–4 s–1. In the absence of noticeable grain growth, the ultrafine-grained alloy maintains the strength up to 380 MPa after SP deformation, which considerably exceeds the value (250 MPa) for the alloy in the peak-aged coarse-grain state. This finding opens pathways to form high-strength articles of Al-Mg-Si alloys after superplastic forming. Full article
(This article belongs to the Special Issue Recent Advances on Mechanical Properties and Microstructural Features of Alloy/Steel)
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18 pages, 8332 KiB  
Article
Influence of Grain Orientation and Grain Boundary Features on Local Stress State of Cu-8Al-11Mn Alloy Investigated Using Crystal Plasticity Finite Element Method
by Ce Zheng, Lijun Xu, Xiaohui Feng, Qiuyan Huang, Yingju Li, Zhongwu Zhang and Yuansheng Yang
Materials 2022, 15(19), 6950; https://doi.org/10.3390/ma15196950 - 7 Oct 2022
Cited by 4 | Viewed by 2330
Abstract
Reducing the local stress in the vicinity of the grain boundaries is a favorable way to improve the super-elastic properties of super-elastic alloys. The crystal plasticity finite element method (CPFEM) was applied in this study to simulate the deformation behavior and local stress [...] Read more.
Reducing the local stress in the vicinity of the grain boundaries is a favorable way to improve the super-elastic properties of super-elastic alloys. The crystal plasticity finite element method (CPFEM) was applied in this study to simulate the deformation behavior and local stress of a super-elastic Cu-8Al-11Mn (wt.%) alloy containing single grains with various orientations, columnar grains with different misorientation angles, and tri-crystals with distinct grain boundary morphologies. The results indicated that the stress distribution of single grains presented obvious orientation dependence during deformation. Uniformly distributed stress was observed in grains with orientations of 0° and 90° when more slip systems were activated during deformation. With the increase in the misorientation angles of columnar grains, the stresses in the vicinity of the grain boundaries increased, which was related to the difference in the shear stress of the slip systems in adjacent grains. When the difference in the shear stress of the slip systems in two adjacent grains was large, a local stress concentration formed in the vicinity of the grain boundary. Compared with the triple-junction grain boundaries, the local stresses of the straight and vertical grain boundaries were smaller, which was closely related to the number of activated slip systems on both sides of the grain boundary. The above results were obtained experimentally and could be used to design super-elastic alloys with high performance. Full article
(This article belongs to the Special Issue Application of Advanced Metal-Forming Technology in Light-Weight Alloys)
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60 pages, 33352 KiB  
Review
The Influence of Surface Texturing of Ceramic and Superhard Cutting Tools on the Machining Process—A Review
by Sergey N. Grigoriev, Thet Naing Soe, Khaled Hamdy, Yuri Pristinskiy, Alexander Malakhinsky, Islamutdin Makhadilov, Vadim Romanov, Ekaterina Kuznetsova, Pavel Podrabinnik, Alexandra Yu. Kurmysheva, Anton Smirnov and Nestor Washington Solís Pinargote
Materials 2022, 15(19), 6945; https://doi.org/10.3390/ma15196945 - 6 Oct 2022
Cited by 9 | Viewed by 3379
Abstract
Machining is an indispensable manufacturing process for a wide range of engineering materials, such as metals, ceramics, and composite materials, in which the tool wear is a serious problem, which affects not only the costs and productivity but also the quality of the [...] Read more.
Machining is an indispensable manufacturing process for a wide range of engineering materials, such as metals, ceramics, and composite materials, in which the tool wear is a serious problem, which affects not only the costs and productivity but also the quality of the machined components. Thus, the modification of the cutting tool surface by application of textures on their surfaces is proposed as a very promising method for improving tool life. Surface texturing is a relatively new surface engineering technology, where microscale or nanoscale surface textures are generated on the cutting tool through a variety of techniques in order to improve tribological properties of cutting tool surfaces by reducing the coefficient of friction and increasing wear resistance. In this paper, the studies carried out to date on the texturing of ceramic and superhard cutting tools have been reviewed. Furthermore, the most common methods for creating textures on the surfaces of different materials have been summarized. Moreover, the parameters that are generally used in surface texturing, which should be indicated in all future studies of textured cutting tools in order to have a better understanding of its effects in the cutting process, are described. In addition, this paper proposes a way in which to classify the texture surfaces used in the cutting tools according to their geometric parameters. This paper highlights the effect of ceramic and superhard textured cutting tools in improving the machining performance of difficult-to-cut materials, such as coefficient of friction, tool wear, cutting forces, cutting temperature, and machined workpiece roughness. Finally, a conclusion of the analyzed papers is given. Full article
(This article belongs to the Special Issue Advanced Ceramics and Composites: Design, Structure, Processing, Properties, and Applications)
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13 pages, 3942 KiB  
Article
Relation between Ga Vacancies, Photoluminescence, and Growth Conditions of MOVPE-Prepared GaN Layers
by Alice Hospodková, Jakub Čížek, František Hájek, Tomáš Hubáček, Jiří Pangrác, Filip Dominec, Karla Kuldová, Jan Batysta, Maciej O. Liedke, Eric Hirschmann, Maik Butterling and Andreas Wagner
Materials 2022, 15(19), 6916; https://doi.org/10.3390/ma15196916 - 5 Oct 2022
Cited by 6 | Viewed by 2433
Abstract
A set of GaN layers prepared by metalorganic vapor phase epitaxy under different technological conditions (growth temperature carrier gas type and Ga precursor) were investigated using variable energy positron annihilation spectroscopy (VEPAS) to find a link between technological conditions, GaN layer properties, and [...] Read more.
A set of GaN layers prepared by metalorganic vapor phase epitaxy under different technological conditions (growth temperature carrier gas type and Ga precursor) were investigated using variable energy positron annihilation spectroscopy (VEPAS) to find a link between technological conditions, GaN layer properties, and the concentration of gallium vacancies (VGa). Different correlations between technological parameters and VGa concentration were observed for layers grown from triethyl gallium (TEGa) and trimethyl gallium (TMGa) precursors. In case of TEGa, the formation of VGa was significantly influenced by the type of reactor atmosphere (N2 or H2), while no similar behaviour was observed for growth from TMGa. VGa formation was suppressed with increasing temperature for growth from TEGa. On the contrary, enhancement of VGa concentration was observed for growth from TMGa, with cluster formation for the highest temperature of 1100 °C. From the correlation of photoluminescence results with VGa concentration determined by VEPAS, it can be concluded that yellow band luminescence in GaN is likely not connected with VGa; additionally, increased VGa concentration enhances excitonic luminescence. The probable explanation is that VGa prevent the formation of some other highly efficient nonradiative defects. Possible types of such defects are suggested. Full article
(This article belongs to the Special Issue Growth and Characteristics of Nitride Semiconductor Layers)
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14 pages, 4224 KiB  
Article
Selective Etching of Si versus Si1−xGex in Tetramethyl Ammonium Hydroxide Solutions with Surfactant
by Yongjoon Choi, Choonghee Cho, Dongmin Yoon, Joosung Kang, Jihye Kim, So Young Kim, Dong Chan Suh and Dae-Hong Ko
Materials 2022, 15(19), 6918; https://doi.org/10.3390/ma15196918 - 5 Oct 2022
Viewed by 3148
Abstract
We investigated the selective etching of Si versus Si1−xGex with various Ge concentrations (x = 0.13, 0.21, 0.30, 0.44) in tetramethyl ammonium hydroxide (TMAH) solution. Our results show that the Si1−xGex with a higher Ge concentration was [...] Read more.
We investigated the selective etching of Si versus Si1−xGex with various Ge concentrations (x = 0.13, 0.21, 0.30, 0.44) in tetramethyl ammonium hydroxide (TMAH) solution. Our results show that the Si1−xGex with a higher Ge concentration was etched slower due to the reduction in the Si(Ge)–OH bond. Owing to the difference in the etching rate, Si was selectively etched in the Si0.7Ge0.3/Si/Si0.7Ge0.3 multi-layer. The etching rate of Si depends on the Si surface orientation, as TMAH is an anisotropic etchant. The (111) and (010) facets were formed in TMAH, when Si was laterally etched in the <110> and <100> directions in the multi-layer, respectively. We also investigated the effect of the addition of Triton X-100 in TMAH on the wet etching process. Our results confirmed that the presence of 0.1 vol% Triton reduced the roughness of the etched Si and Si1−xGex surfaces. Moreover, the addition of Triton to TMAH could change the facet formation from (010) to (011) during Si etching in the <100>-direction. The facet change could reduce the lateral etching rate of Si and consequently reduce selectivity. The decrease in the layer thickness also reduced the lateral Si etching rate in the multi-layer. Full article
(This article belongs to the Special Issue Anisotropic Functional Nanomaterials: Preparations, Characterizations, and Applications)
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11 pages, 13571 KiB  
Article
Gold-Nanoparticle-Coated Magnetic Beads for ALP-Enzyme-Based Electrochemical Immunosensing in Human Plasma
by Seo-Eun Lee, Se-Eun Jeong, Jae-Sang Hong, Hyungsoon Im, Sei-Young Hwang, Jun Kyun Oh and Seong-Eun Kim
Materials 2022, 15(19), 6875; https://doi.org/10.3390/ma15196875 - 3 Oct 2022
Cited by 5 | Viewed by 3429
Abstract
A simple and sensitive AuNP-coated magnetic beads (AMB)-based electrochemical biosensor platform was fabricated for bioassay. In this study, AuNP-conjugated magnetic particles were successfully prepared using biotin–streptavidin conjugation. The morphology and structure of the nanocomplex were characterized by scanning electron microscopy (SEM) with energy-dispersive [...] Read more.
A simple and sensitive AuNP-coated magnetic beads (AMB)-based electrochemical biosensor platform was fabricated for bioassay. In this study, AuNP-conjugated magnetic particles were successfully prepared using biotin–streptavidin conjugation. The morphology and structure of the nanocomplex were characterized by scanning electron microscopy (SEM) with energy-dispersive X-ray analysis (EDX) and UV–visible spectroscopy. Moreover, cyclic voltammetry (CV) was used to investigate the effect of AuNP-MB on alkaline phosphatase (ALP) for electrochemical signal enhancement. An ALP-based electrochemical (EC) immunoassay was performed on the developed AuNP-MB complex with indium tin oxide (ITO) electrodes. Subsequently, the concentration of capture antibodies was well-optimized on the AMB complex via biotin–avidin conjugation. Lastly, the developed AuNP-MB immunoassay platform was verified with extracellular vesicle (EV) detection via immune response by showing the existence of EGFR proteins on glioblastoma multiforme (GBM)-derived EVs (108 particle/mL) spiked in human plasma. Therefore, the signal-enhanced ALP-based EC biosensor on AuNP-MB was favorably utilized as an immunoassay platform, revealing the potential application of biosensors in immunoassays in biological environments. Full article
(This article belongs to the Special Issue Application of Nanoparticles as Biosensors in the Biomedical Field)
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17 pages, 4704 KiB  
Article
Flexible Perfluoropolyethers-Functionalized CNTs-Based UHMWPE Composites: A Study on Hydrogen Evolution, Conductivity and Thermal Stability
by Maurizio Sansotera, Valeria Marona, Piergiorgio Marziani, Nadka Tzankova Dintcheva, Elisabetta Morici, Rossella Arrigo, Gianlorenzo Bussetti, Walter Navarrini and Luca Magagnin
Materials 2022, 15(19), 6883; https://doi.org/10.3390/ma15196883 - 3 Oct 2022
Cited by 3 | Viewed by 1838
Abstract
Flexible conductive composites based on ultra-high molecular weight polyethylene (UHMWPE) filled with multi-walled carbon nanotubes (CNTs) modified by perfluoropolyethers (PFPEs) were produced. The bonding of PFPE chains, added in 1:1 and 2:1 weight ratios, on CNTs influences the dispersion of nanotubes in the [...] Read more.
Flexible conductive composites based on ultra-high molecular weight polyethylene (UHMWPE) filled with multi-walled carbon nanotubes (CNTs) modified by perfluoropolyethers (PFPEs) were produced. The bonding of PFPE chains, added in 1:1 and 2:1 weight ratios, on CNTs influences the dispersion of nanotubes in the UHMWPE matrix due to the non-polar nature of the polymer, facilitating the formation of nanofillers-rich conductive pathways and improving composites’ electrical conductivity (two to five orders of magnitude more) in comparison to UHMWPE-based nanocomposites obtained with pristine CNTs. Electrochemical atomic force microscopy (EC-AFM) was used to evaluate the morphological changes during cyclic voltammetry (CV). The decrease of the overpotential for hydrogen oxidation peaks in samples containing PFPE-functionalized CNTs and hydrogen production (approximately −1.0 V vs. SHE) suggests that these samples could find application in fuel cell technology as well as in hydrogen storage devices. Carbon black-containing composites were prepared for comparative study with CNTs containing nanocomposites. Full article
(This article belongs to the Section Advanced Composites)
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19 pages, 4196 KiB  
Article
Bright UV-C Phosphors with Excellent Thermal Stability—Y1−xScxPO4 Solid Solutions
by Dmitry Spassky, Andrey Vasil’ev, Vitali Nagirnyi, Irina Kudryavtseva, Dina Deyneko, Ivan Nikiforov, Ildar Kondratyev and Boris Zadneprovski
Materials 2022, 15(19), 6844; https://doi.org/10.3390/ma15196844 - 2 Oct 2022
Cited by 10 | Viewed by 1993
Abstract
The structural and luminescence properties of undoped Y1−xScxPO4 solid solutions have been studied. An intense thermally stable emission with fast decay (τ1/e ~ 10−7 s) and a band position varying from 5.21 to 5.94 eV [...] Read more.
The structural and luminescence properties of undoped Y1−xScxPO4 solid solutions have been studied. An intense thermally stable emission with fast decay (τ1/e ~ 10−7 s) and a band position varying from 5.21 to 5.94 eV depending on the Sc/Y ratio is detected and ascribed to the 2p O-3d Sc self-trapped excitons. The quantum yield of the UV-C emission, also depending on the Sc/Y ratio, reaches 34% for the solid solution with x = 0.5 at 300 K. It is shown by a combined analysis of theoretical and experimental data that the formation of Sc clusters occurs in the solid solutions studied. The clusters facilitate the creation of energy wells at the conduction band bottom, which enables deep localization of electronic excitations and the creation of luminescence centers characterized by high quantum yield and thermal stability of the UV-C emission. Full article
(This article belongs to the Collection Luminescent Materials)
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17 pages, 9975 KiB  
Article
Microstructure and Mechanical Properties of Hot-Extruded Mg–Zn–Ga–(Y) Biodegradable Alloys
by Viacheslav Bazhenov, Anna Li, Stanislav Tavolzhanskii, Andrey Bazlov, Natalia Tabachkova, Andrey Koltygin, Alexander Komissarov and Kwang Seon Shin
Materials 2022, 15(19), 6849; https://doi.org/10.3390/ma15196849 - 2 Oct 2022
Cited by 10 | Viewed by 2290
Abstract
Magnesium alloys are attractive candidates for use as temporary fixation devices in osteosynthesis because they have a density and Young’s modulus similar to those of cortical bone. One of the main requirements for biodegradable implants is its substitution by tissues during the healing [...] Read more.
Magnesium alloys are attractive candidates for use as temporary fixation devices in osteosynthesis because they have a density and Young’s modulus similar to those of cortical bone. One of the main requirements for biodegradable implants is its substitution by tissues during the healing process. In this article, the Mg–Zn–Ga–(Y) alloys were investigated that potentially can increase the bone growth rate by release of Ga ions during the degradation process. Previously, the effectiveness of Ga ions on bone tissue regeneration has been proved by clinical tests. This work is the first systematic study on the microstructure and mechanical properties of Mg–Zn–Y alloys containing Ga as an additional major alloying element prepared by the hot-extrusion process. The microstructure and phase composition of the Mg–Zn–Ga–(Y) alloys in as-cast, heat-treated, and extruded conditions were analyzed. In addition, it was shown that the use of hot extrusion produces Mg–Zn–Ga–(Y) alloys with favorable mechanical properties. The tensile yield strength, ultimate tensile strength, and elongation at fracture of the MgZn4Ga4 alloy extruded at 150 °C were 256 MPa, 343 MPa, and 14.2%, respectively. Overall, MgZn4Ga4 alloy is a perspective for applications in implants for osteosynthesis with improved bone regeneration ability. Full article
(This article belongs to the Special Issue Hot Deformation Behavior of Magnesium Alloys)
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12 pages, 3621 KiB  
Article
Effects of Grain Refinement and Thermal Aging on Atomic Scale Local Structures of Ultra-Fine Explosives by X-ray Total Scattering
by Jiangtao Xing, Weili Wang, Shiliang Huang, Maohua Du, Bing Huang, Yousong Liu, Shanshan He, Tianle Yao, Shichun Li and Yu Liu
Materials 2022, 15(19), 6835; https://doi.org/10.3390/ma15196835 - 1 Oct 2022
Cited by 3 | Viewed by 1683
Abstract
The atomic scale local structures affect the initiation performance of ultra-fine explosives according to the stimulation results of hot spot formation. However, the experimental characterization of local structures in ultra-fine explosives has been rarely reported, due to the difficulty in application of characterization [...] Read more.
The atomic scale local structures affect the initiation performance of ultra-fine explosives according to the stimulation results of hot spot formation. However, the experimental characterization of local structures in ultra-fine explosives has been rarely reported, due to the difficulty in application of characterization methods having both high resolution in and small damage to unstable organic explosive materials. In this work, X-ray total scattering was explored to investigate the atomic scale local distortion of two widely applicable ultra-fine explosives, LLM-105 and HNS. The experimental spectra of atomic pair distribution function (PDF) derived from scattering results were fitted by assuming rigid ring structures in molecules. The effects of grain refinement and thermal aging on the atomic scale local structure were investigated, and the changes in both the length of covalent bonds have been identified. Results indicate that by decreasing the particle size of LLM-105 and HNS from hundreds of microns to hundreds of nanometers, the crystal structures remain, whereas the molecular configuration slightly changes and the degree of structural disorder increases. For example, the average length of covalent bonds in LLM-105 reduces from 1.25 Å to 1.15 Å, whereas that in HNS increases from 1.25 Å to 1.30 Å, which is possibly related to the incomplete crystallization process and internal stress. After thermal aging of ultra-fine LLM-105 and HNS, the degree of structural disorder decreases, and the distortion in molecules formed in the synthesis process gradually healed. The average length of covalent bonds in LLM-105 increases from 1.15 Å to 1.27 Å, whereas that in HNS reduces from 1.30 Å to 1.20 Å. The possible reason is that the atomic vibration in the molecule intensifies during the heat aging treatment, and the internal stress was released through changes in molecular configuration, and thus the atomic scale distortion gradually heals. The characterization method and findings in local structures obtained in this work may pave the path to deeply understand the relationship between the defects and performance of ultra-fine explosives. Full article
(This article belongs to the Section Advanced Materials Characterization)
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27 pages, 10406 KiB  
Article
Three-Dimensional Numerical Simulation of Grain Growth during Selective Laser Melting of 316L Stainless Steel
by Feng Xu, Feiyu Xiong, Ming-Jian Li and Yanping Lian
Materials 2022, 15(19), 6800; https://doi.org/10.3390/ma15196800 - 30 Sep 2022
Cited by 10 | Viewed by 3626
Abstract
The grain structure of the selective laser melting additive manufactured parts has been shown to be heterogeneous and spatially non-uniform compared to the traditional manufacturing process. However, the complex formation mechanism of these unique grain structures is hard to reveal using the experimental [...] Read more.
The grain structure of the selective laser melting additive manufactured parts has been shown to be heterogeneous and spatially non-uniform compared to the traditional manufacturing process. However, the complex formation mechanism of these unique grain structures is hard to reveal using the experimental method alone. In this study, we presented a high-fidelity 3D numerical model to address the grain growth mechanisms during the selective laser melting of 316 stainless steel, including two heating modes, i.e., conduction mode and keyhole mode melting. In the numerical model, the powder-scale thermo-fluid dynamics are simulated using the finite volume method with the volume of fluid method. At the same time, the grain structure evolution is sequentially predicted by the cellular automaton method with the predicted temperature field and the as-melted powder bed configuration as input. The simulation results agree well with the experimental data available in the literature. The influence of the process parameters and the keyhole and keyhole-induced void on grain structure formation are addressed in detail. The findings of this study are helpful to the optimization of process parameters for tailoring the microstructure of fabricated parts with expected mechanical properties. Full article
(This article belongs to the Special Issue Experimental Research and Numerical Simulations of Metal Additive Manufacturing)
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16 pages, 8996 KiB  
Article
Simulation of the Refractive Index Variation and Validation of the Form Deviation in Precisely Molded Chalcogenide Glass Lenses (IRG 26) Considering the Stress and Structure Relaxation
by Cheng Jiang, Carlos Marin Tovar, Jan-Helge Staasmeyer, Marcel Friedrichs, Tim Grunwald and Thomas Bergs
Materials 2022, 15(19), 6756; https://doi.org/10.3390/ma15196756 - 29 Sep 2022
Cited by 5 | Viewed by 2520
Abstract
Precise infrared (IR) optics are core elements of infrared cameras for thermal imaging and night vision applications and can be manufactured directly or using a replicative process. For instance, precision glass molding (PGM) is a replicative manufacturing method that meets the demand of [...] Read more.
Precise infrared (IR) optics are core elements of infrared cameras for thermal imaging and night vision applications and can be manufactured directly or using a replicative process. For instance, precision glass molding (PGM) is a replicative manufacturing method that meets the demand of producing precise and accurate glass optics in a cost-efficient manner. However, several iterations in the PGM process are applied to compensate the induced form deviation and the index drop after molding. The finite element method (FEM) is utilized to simulate the thermomechanical process, predicting the optical properties of molded chalcogenide lenses and thus preventing costly iterations. Prior to FEM modelling, self-developed glass characterization methods for the stress and structure relaxation of chalcogenide glass IRG 26 are implemented. Additionally, a ray-tracing method is developed in this work to calculate the optical path difference (OPD) based on the mesh structure results from the FEM simulation. The developed method is validated and conducted during the production of molded lenses. Full article
(This article belongs to the Section Optical and Photonic Materials)
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26 pages, 8954 KiB  
Review
Frontier and Hot Topics of Pulsed Fiber Lasers via CiteSpace Scientometric Analysis: Passively Mode-Locked Fiber Lasers with Real Saturable Absorbers Based on Two-Dimensional Materials
by Wen Zhou, Xiuyang Pang, Hanke Zhang, Qiang Yu, Fangqi Liu, Wenyue Wang, Yikun Zhao, Yan Lu and Zixin Yang
Materials 2022, 15(19), 6761; https://doi.org/10.3390/ma15196761 - 29 Sep 2022
Cited by 13 | Viewed by 3112
Abstract
Pulsed fiber lasers, with high peak power and narrow pulse widths, have been proven to be an important tool for a variety of fields of application. In this work, frontier and hot topics in pulsed fiber lasers were analyzed with 11,064 articles. Benefitting [...] Read more.
Pulsed fiber lasers, with high peak power and narrow pulse widths, have been proven to be an important tool for a variety of fields of application. In this work, frontier and hot topics in pulsed fiber lasers were analyzed with 11,064 articles. Benefitting from the scientometric analysis capabilities of CiteSpace, the analysis found that passively mode-locked fiber lasers with saturable absorbers (SAs) based on two-dimensional (2D) materials have become a hot research topic in the field of pulsed fiber lasers due to the advantages of self-starting operation, high stability, and good compatibility. The excellent nonlinear optical properties exhibited by 2D materials at nanometer-scale thicknesses have become a particularly popular research topic; the research has paved the way for exploring its wider applications. We summarize the performance of several typical 2D materials in ultrafast fiber lasers, such as graphene, topological insulators (TIs), transition metal dichalcogenides (TMDs), and black phosphorus (BP). Meanwhile, we review and analyze the direction of the development of 2D SAs for ultrafast fiber lasers. Full article
(This article belongs to the Special Issue Fiber Lasers and Non-Linear Optics of Materials)
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10 pages, 2425 KiB  
Article
Study of Carrier Mobilities in 4H-SiC MOSFETS Using Hall Analysis
by Suman Das, Yongju Zheng, Ayayi Ahyi, Marcelo A. Kuroda and Sarit Dhar
Materials 2022, 15(19), 6736; https://doi.org/10.3390/ma15196736 - 28 Sep 2022
Cited by 11 | Viewed by 3546
Abstract
The channel conduction in 4H-SiC metal–oxide–semiconductor field effect transistors (MOSFETs) are highly impacted by charge trapping and scattering at the interface. Even though nitridation reduces the interface trap density, scattering still plays a crucial role in increasing the channel resistance in these transistors. [...] Read more.
The channel conduction in 4H-SiC metal–oxide–semiconductor field effect transistors (MOSFETs) are highly impacted by charge trapping and scattering at the interface. Even though nitridation reduces the interface trap density, scattering still plays a crucial role in increasing the channel resistance in these transistors. In this work, the dominant scattering mechanisms are distinguished for inversion layer electrons and holes using temperature and body-bias-dependent Hall measurements on nitrided lateral 4H-SiC MOSFETs. The effect of the transverse electric field (Eeff) on carrier mobility is analyzed under strong inversion condition where surface roughness scattering becomes prevalent. Power law dependencies of the electron and hole Hall mobility for surface roughness scattering are determined to be Eeff−1.8 and Eeff−2.4, respectively, analogous to those of silicon MOSFETs. Moreover, for n-channel MOSFETs, the effect of phonon scattering is observed at zero body bias, whereas in p-channel MOSFETs, it is observed only under negative body biases. Along with the identification of regimes governed by different scattering mechanisms, these results highlight the importance of the selection of substrate doping and of Eeff in controlling the value of channel mobility in 4H-SiC MOSFETs. Full article
(This article belongs to the Special Issue Silicon Carbide: Material Growth, Device Processing and Applications)
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17 pages, 3510 KiB  
Article
Study on the Stability of Bio-Oil Modified Prime Coat Oil Based on Molecular Dynamics
by Shuang Shi, Lanqin Lin, Zhaoguang Hu, Linhao Gu and Yanning Zhang
Materials 2022, 15(19), 6737; https://doi.org/10.3390/ma15196737 - 28 Sep 2022
Cited by 11 | Viewed by 2164
Abstract
To explore the effect of different emulsifier contents on the stability performance of biomass-emulsified asphalt, three types of emulsified asphalt with 1%, 3%, and 5% anionic emulsifiers were prepared and analyzed by molecular dynamics simulation and macroscopic experiments. Firstly, we used molecular simulation [...] Read more.
To explore the effect of different emulsifier contents on the stability performance of biomass-emulsified asphalt, three types of emulsified asphalt with 1%, 3%, and 5% anionic emulsifiers were prepared and analyzed by molecular dynamics simulation and macroscopic experiments. Firstly, we used molecular simulation software (Material Studio, MS) to construct a model of biomass-emulsified asphalt with different emulsifier contents and analyzed the microscopic mechanism of the emulsifier to improve the stability of the emulsified asphalt by the radial distribution function, interaction energy, interfacial layer thickness, and solubility parameters of the emulsified asphalt system with different emulsifier contents. The results were validated by macro and micro tests including storage stability, particle size determination, and infrared spectroscopy. The results show that at low emulsifier contents, the emulsifier can reduce the interfacial tension between the oil–water interface and expand the transition region between the two phases (interfacial layer thickness), which will prevent interparticle agglomeration and reduce the emulsion particle size, thus reducing the settling rate and ensuring the stability of the emulsion. When the emulsifier content is further increased beyond the critical micelle concentration, the emulsifiers will agglomerate with each other and show larger peaks in the radial distribution function, and the phenomenon of emulsifier agglomeration will appear in the five-day storage stability test, resulting in a corresponding decrease in the proximity of the infrared absorption peak area ratio in the same wavelength band of the upper and lower layers of the biomass-emulsified asphalt, and the emulsion stability decreases instead. Full article
(This article belongs to the Special Issue Sustainable Recycling Techniques of Pavement Materials)
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13 pages, 5635 KiB  
Article
Excellent Thermoelectric Performance of 2D CuMN2 (M = Sb, Bi; N = S, Se) at Room Temperature
by Wenyu Fang, Yue Chen, Kuan Kuang and Mingkai Li
Materials 2022, 15(19), 6700; https://doi.org/10.3390/ma15196700 - 27 Sep 2022
Cited by 9 | Viewed by 2570
Abstract
2D copper-based semiconductors generally possess low lattice thermal conductivity due to their strong anharmonic scattering and quantum confinement effect, making them promising candidate materials in the field of high-performance thermoelectric devices. In this work, we proposed four 2D copper-based materials, namely CuSbS2 [...] Read more.
2D copper-based semiconductors generally possess low lattice thermal conductivity due to their strong anharmonic scattering and quantum confinement effect, making them promising candidate materials in the field of high-performance thermoelectric devices. In this work, we proposed four 2D copper-based materials, namely CuSbS2, CuSbSe2, CuBiS2, and CuBiSe2. Based on the framework of density functional theory and Boltzmann transport equation, we revealed that the monolayers possess high stability and narrow band gaps of 0.57~1.10 eV. Moreover, the high carrier mobilities (102~103 cm2·V−1·s−1) of these monolayers lead to high conductivities (106~107 Ω−1·m−1) and high-power factors (18.04~47.34 mW/mK2). Besides, as the strong phonon-phonon anharmonic scattering, the monolayers also show ultra-low lattice thermal conductivities of 0.23~3.30 W/mK at 300 K. As results show, all the monolayers for both p-type and n-type simultaneously show high thermoelectric figure of merit (ZT) of about 0.91~1.53 at room temperature. Full article
(This article belongs to the Special Issue Materials Physics in Thermoelectric Materials)
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14 pages, 1178 KiB  
Article
Evaluation of the Color Stability, Water Sorption, and Solubility of Current Resin Composites
by Wenkai Huang, Ling Ren, Yuyao Cheng, Minghua Xu, Wenji Luo, Desong Zhan, Hidehiko Sano and Jiale Fu
Materials 2022, 15(19), 6710; https://doi.org/10.3390/ma15196710 - 27 Sep 2022
Cited by 34 | Viewed by 3694
Abstract
This study aims to assess the color stability, water sorption, and solubility of 11 resin composites as commercially available dental products. Twenty samples (10 mm in diameter and 2 mm in thickness) of each material were fabricated using a customized silicone mold, followed [...] Read more.
This study aims to assess the color stability, water sorption, and solubility of 11 resin composites as commercially available dental products. Twenty samples (10 mm in diameter and 2 mm in thickness) of each material were fabricated using a customized silicone mold, followed by immersion in each of curry, coffee, wine, and distilled water for 28 days (n = 5). Baseline shade and color changes (ΔE) were measured using a reflection spectrophotometer. The CIE L*, a*, b* system was used to evaluate the color changes. Five samples of each resin composite were applied to test water sorption and solubility according to ISO 4049:2009. As a result, the ∆E values were significantly influenced by each of the three factors (composition of material, solution, time) and the interactions between them (p < 0.001). Highest resistance to discoloration was achieved by Ceram.X One Universal (CXU), followed by Magnafill Putty (MP). Generally, microhybrid composites showed fewer color changes than nanohybrid composites and giomers. DX. Universal and Filtek Z350 XT showed the highest ΔE values in all colorants. All materials tested in this study fulfilled the criteria of ISO 4049:2009; CXU and MP had the lowest water sorption and solubility. The Pearson test showed statistically significant positive correlations between water sorption and ΔE and between solubility and ΔE. Full article
(This article belongs to the Special Issue Advanced Restorative Dental Composite Resins: Research and Development)
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12 pages, 5057 KiB  
Article
Ultrahigh Piezoelectric Strains in PbZr1−xTixO3 Single Crystals with Controlled Ti Content Close to the Tricritical Point
by Iwona Lazar, Roger William Whatmore, Andrzej Majchrowski, Anthony Mike Glazer, Dariusz Kajewski, Janusz Koperski, Andrzej Soszyński, Julita Piecha, Barbara Loska and Krystian Roleder
Materials 2022, 15(19), 6708; https://doi.org/10.3390/ma15196708 - 27 Sep 2022
Cited by 5 | Viewed by 2049
Abstract
Intensive investigations of PbZr1-xTixO3 (PZT) materials with the ABO3 perovskite structure are connected with their extraordinary piezoelectric properties. Especially well known are PZT ceramics at the Morphotropic Phase Boundary (MPB), with x~0.48, whose applications are the most [...] Read more.
Intensive investigations of PbZr1-xTixO3 (PZT) materials with the ABO3 perovskite structure are connected with their extraordinary piezoelectric properties. Especially well known are PZT ceramics at the Morphotropic Phase Boundary (MPB), with x~0.48, whose applications are the most numerous among ferroelectrics. These piezoelectric properties are often obtained by doping with various ions at the B sites. Interestingly, we have found similar properties for undoped PZT single crystals with low Ti content, for which we have confirmed the existence of the tricritical point near x~0.06. For a PbZr0.95 ± 0.01Ti0.05∓ 0.01O3 crystal, we describe the ultrahigh strain, dielectric, optical and piezoelectric properties. We interpret the ultrahigh strain observed in the region of the antiferroelectric–ferroelectric transition as an inverse piezoelectric effect generated by the coexistence of domains of different symmetries. The complex domain coexistence was confirmed by determining optical indicatrix orientations in domains. The piezoelectric coefficient in this region reached an extremely high value of 5000 pm/V. We also verified that the properties of the PZT single crystals from the region near the tricritical point are incredibly susceptible to a slight deviation in the Ti content. Full article
(This article belongs to the Special Issue Emerging Dielectric, Piezoelectric and Ferroelectric Ceramic and Crystalline Materials and Their Applications)
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13 pages, 4286 KiB  
Article
Dissolution of β-C2S Cement Clinker: Part 2 Atomistic Kinetic Monte Carlo (KMC) Upscaling Approach
by Mohammadreza Izadifar, Neven Ukrainczyk, Khondakar Mohammad Salah Uddin, Bernhard Middendorf and Eduardus Koenders
Materials 2022, 15(19), 6716; https://doi.org/10.3390/ma15196716 - 27 Sep 2022
Cited by 21 | Viewed by 2881
Abstract
Cement clinkers containing mainly belite (β-C2S as a model crystal), replacing alite, offer a promising solution for the development of environmentally friendly solutions to reduce the high level of CO2 emissions in the production of Portland cement. However, the much [...] Read more.
Cement clinkers containing mainly belite (β-C2S as a model crystal), replacing alite, offer a promising solution for the development of environmentally friendly solutions to reduce the high level of CO2 emissions in the production of Portland cement. However, the much lower reactivity of belite compared to alite limits the widespread use of belite cements. Therefore, this work presents a fundamental atomistic computational approach for comprehending and quantifying the mesoscopic forward dissolution rate of β-C2S, applied to two reactive crystal facets of (100) and (1¯00). For this, an atomistic kinetic Monte Carlo (KMC) upscaling approach for cement clinker was developed. It was based on the calculated activation energies (ΔG*) under far-from-equilibrium conditions obtained by a molecular dynamic simulation using the combined approach of ReaxFF and metadynamics, as described in the Part 1 paper in this Special Issue. Thus, the individual atomistic dissolution rates were used as input parameters for implementing the KMC upscaling approach coded in MATLAB to study the dissolution time and morphology changes at the mesoscopic scale. Four different cases and 21 event scenarios were considered for the dissolution of calcium atoms (Ca) and silicate monomers. For this purpose, the (100) and (1¯00) facets of a β-C2S crystal were considered using periodic boundary conditions (PBCs). In order to demonstrate the statistical nature of the KMC approach, 40 numerical realizations were presented. The major findings showed a striking layer-by-layer dissolution mechanism in the case of an ideal crystal, where the total dissolution rate was limited by the much slower dissolution of the silicate monomer compared to Ca. The introduction of crystal defects, namely cutting the edges at two crystal boundaries, increased the overall average dissolution rate by a factor of 519. Full article
(This article belongs to the Special Issue Mathematical Modeling of Building Materials)
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12 pages, 3274 KiB  
Article
Immediate and Long-Term Radiopacity and Surface Morphology of Hydraulic Calcium Silicate-Based Materials
by Goda Bilvinaite, Saulius Drukteinis, Vilma Brukiene and Sivaprakash Rajasekharan
Materials 2022, 15(19), 6635; https://doi.org/10.3390/ma15196635 - 24 Sep 2022
Cited by 8 | Viewed by 2406
Abstract
The present study aimed to evaluate and compare the radiopacity and surface morphology of AH Plus Bioceramic Sealer (AHPB), Bio-C Sealer (BIOC), Biodentine (BD), BioRoot RCS (BR), Grey-MTAFlow (GMF), White-MTAFlow (WMF), TotalFill BC Sealer (TF), and TotalFill BC Sealer HiFlow (TFHF) at different [...] Read more.
The present study aimed to evaluate and compare the radiopacity and surface morphology of AH Plus Bioceramic Sealer (AHPB), Bio-C Sealer (BIOC), Biodentine (BD), BioRoot RCS (BR), Grey-MTAFlow (GMF), White-MTAFlow (WMF), TotalFill BC Sealer (TF), and TotalFill BC Sealer HiFlow (TFHF) at different time moments—30 min, 24 h, and 28 days. Ten specimens of each material were prepared according to the ISO-6876:2012 standard and radiographed next to an aluminum step wedge using a digital sensor. The specimens were stored in a gelatinized Hank’s balanced salt solution at 37 °C between assessments. The mean grayscale values of each specimen were converted into equivalent aluminum thickness by a linear regression model. Characterization of the surface morphology was performed by using a scanning electron microscope at ×4.0k and ×10.0k magnifications. The radiographic analysis revealed that all the tested materials exceeded the ISO-specified limit of 3 mm Al, with the highest radiopacity presented by AHPB and the lowest by BD. None of the tested materials demonstrated considerable variances between the 30 min and the 24 h radiopacity level (p < 0.05), and statistically significant long-term radiopacity changes were exhibited by BR, TFHF, and TF (p > 0.05). All the specimens demonstrated a common feature of limited precipitate formation, with numerous unreacted particles still presented on the surface after 24 h, whereas the particle rearrangement and the deposition of precipitates were clearly observed after 28 days. Full article
(This article belongs to the Special Issue Biomaterials for Medical and Dental Application)
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10 pages, 3795 KiB  
Article
Effects of the Parent Alloy Microstructure on the Thermal Stability of Nanoporous Au
by Andrea Pinna, Giorgio Pia, Roberta Licheri and Luca Pilia
Materials 2022, 15(19), 6621; https://doi.org/10.3390/ma15196621 - 23 Sep 2022
Cited by 2 | Viewed by 1572
Abstract
Nanoporous (NP) metals represent a unique class of materials with promising properties for a wide set of applications in advanced technology, from catalysis and sensing to lightweight structural materials. However, they typically suffer from low thermal stability, which results in a coarsening behavior [...] Read more.
Nanoporous (NP) metals represent a unique class of materials with promising properties for a wide set of applications in advanced technology, from catalysis and sensing to lightweight structural materials. However, they typically suffer from low thermal stability, which results in a coarsening behavior not yet fully understood. In this work, we focused precisely on the coarsening process undergone by NP Au, starting from the analysis of data available in the literature and addressing specific issues with suitably designed experiments. We observe that annealing more easily induces densification in systems with short characteristic lengths. The NP Au structures obtained by dealloying of mechanically alloyed AuAg precursors exhibit lower thermal stability than several NP Au samples discussed in the literature. Similarly, NP Au samples prepared by annealing the precursor alloy before dealloying display enhanced resistance to coarsening. We suggest that the microstructure of the precursor alloy, and, in particular, the grain size of the metal phases, can significantly affect the thermal stability of the NP metal. Specifically, the smaller the grain size of the parent alloy, the lower the thermal stability. Full article
(This article belongs to the Special Issue Recent Advances in the Mechanical Properties and Microstructural Features of Porous Materials)
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24 pages, 11073 KiB  
Article
Performance-Based Assessment of Bridges with Novel SMA-Washer-Based Self-Centering Rocking Piers
by Jiawei Chen, Dong Liang, Xin You and Hao Liang
Materials 2022, 15(19), 6589; https://doi.org/10.3390/ma15196589 - 22 Sep 2022
Cited by 5 | Viewed by 2227
Abstract
This study discussed a novel self-centering rocking (SCR) bridge system equipped with shape memory alloy (SMA)-based piers, with a particular focus on the benefit of the SCR bridge system in a life-cycle context. The study commences with an introduction of the SCR bridge [...] Read more.
This study discussed a novel self-centering rocking (SCR) bridge system equipped with shape memory alloy (SMA)-based piers, with a particular focus on the benefit of the SCR bridge system in a life-cycle context. The study commences with an introduction of the SCR bridge system; subsequently, a life-cycle loss and resilience assessment framework for the SCR bridge system is presented. Specifically, the seismic fragility, resilience, and life-cycle loss associated with the SCR and conventional bridge systems were addressed. The proposed life-cycle assessment framework was finally applied to two highway bridges with and without SMA washer-based rocking piers, considering the representative hazard scenarios that could happen within the investigated regions. The results revealed that the novel SCR pier bridge system slightly increased the bearing displacement but extensively reduced the pier curvature ductility due to the rocking mechanism. The SCR bridge system kept a lower life-cycle loss level and exhibited more resilient performance than the conventional bridge, especially in the region with higher seismic intensities. Indirect loss can be significantly larger than the direct loss, specifically for the earthquakes with a relatively low probability of occurrence. The SCR bridge system outperformed the conventional system in terms of recovery time, where a quick recovery after an earthquake and drastically decreased the social and economic losses. Full article
(This article belongs to the Special Issue Shape Memory Alloys for Civil Engineering)
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12 pages, 4339 KiB  
Article
Electric Arc Furnace Dust Recycled in 7075 Aluminum Alloy Composites Fabricated by Spark Plasma Sintering (SPS)
by Elder Soares, Nadège Bouchonneau, Elizeth Alves, Kleber Alves, Oscar Araújo Filho, David Mesguich, Geoffroy Chevallier, Nouhaila Khalile, Christophe Laurent and Claude Estournès
Materials 2022, 15(19), 6587; https://doi.org/10.3390/ma15196587 - 22 Sep 2022
Cited by 3 | Viewed by 2132
Abstract
The reuse of industrial waste, such as electric arc furnace dust (EAFD) as reinforcement in aluminum matrix composites (AMC), is still little explored even though it has shown potential to improve the mechanical properties, such as hardness and mechanical strength, of AMCs. To [...] Read more.
The reuse of industrial waste, such as electric arc furnace dust (EAFD) as reinforcement in aluminum matrix composites (AMC), is still little explored even though it has shown potential to improve the mechanical properties, such as hardness and mechanical strength, of AMCs. To propose a new alternative for EAFD recycling, AA7075-EAFD composites were produced by spark plasma sintering (SPS). The starting powders were prepared by high-energy milling with different weight fractions of EAFD in two particle size ranges added to an AA7075 matrix. SEM shows that the distribution of reinforcement particles in the matrix is homogeneous with no agglomeration of the particles. XRD patterns of initial powders and the SPS-sintered (SPSed) samples suggest that there was no reaction during sintering (no additional peaks were detected). The relative density of all SPSed samples exceeded 96.5%. The Vickers microhardness of the composites tended to increase with increasing EAFD content, increasing from 108 HV (AA7075 without reinforcement) up to 168 HV (56% increase). The maximum microhardness value was obtained when using 15 wt.% EAFD with a particle size smaller than 53 μm (called G1), showing that EAFD presents a promising potential to be applied as reinforcement in AA7075 matrix composites. Full article
(This article belongs to the Special Issue Materials with Advanced Properties Fabricated by Spark Plasma Sintering)
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17 pages, 4643 KiB  
Article
Investigating the Correlation between the Microstructure and Electrical Properties of FeSbO4 Ceramics
by Carlos G. P. Moraes, Robert S. Matos, Cledson dos Santos, Ştefan Ţălu, John M. Attah-Baah, Romualdo S. Silva Junior, Marcelo S. da Silva, Marcos V. S. Rezende, Ronaldo S. Silva and Nilson S. Ferreira
Materials 2022, 15(19), 6555; https://doi.org/10.3390/ma15196555 - 21 Sep 2022
Cited by 6 | Viewed by 2528
Abstract
FeSbO4 powder was prepared using the solid-state reaction method in this work. Afterward, the dense and porous ceramics were obtained by sintering the pressed powder calcined at temperatures of 900 and 1000 °C for 4 h. Rietveld profile analysis of the X-ray [...] Read more.
FeSbO4 powder was prepared using the solid-state reaction method in this work. Afterward, the dense and porous ceramics were obtained by sintering the pressed powder calcined at temperatures of 900 and 1000 °C for 4 h. Rietveld profile analysis of the X-ray powder diffraction data showed that FeSbO4 adopts the trirutile-type structure (space group P42/mnm, with a ≅ 4.63 Å and c ≅ 9.23 Å). SEM images showed that the powder calcined at 900 °C after being sintered at 1200 °C resulted in ceramics of higher crystallinity, larger grains, and consequently, low porosity. The dielectric properties were measured in the frequency range of 10−1 Hz–1 MHz as a function of temperature (25–250 °C). The real (σ′) and imaginary (σ″) parts of the complex conductivity increase with rising annealing temperature for both samples. The real conductivity in the AC region for 𝑓 = 100 kHz was 1.59×10−6 S·cm−1 and 7.04×10−7 S·cm−1 for the ceramic samples obtained from the powder calcined at 900 (C-900) and 1000 °C (C-1000), respectively. Furthermore, the dielectric constants (k′) measured at room temperature and f=100 kHz were 13.77 (C-900) and 6.27 (C-1000), while the activation energies of the grain region were Ea = 0.53 eV and Ea = 0.49 eV, respectively. Similar activation energy (Ea = 0.52 eV and 0.49 eV) was also obtained by the brick-layer model and confirmed by the adjustment of activation energy by DC measurements which indicated an absence of the porosity influence on the parameter. Additionally, loss factor values were obtained to be equal to 3.8 (C-900) and 5.99 (C-1000) for measurements performed at 100 Hz, suggesting a contribution of the conductivity originated from the combination or accommodation of the pores in the grain boundary region. Our results prove that the microstructural factors that play a critical role in the electrical and dielectric properties are the average grain size and the porosity interspersed with the grain boundary region. Full article
(This article belongs to the Special Issue New Progresses in the Development, Microstructure and Properties of Ceramic-Metal Composites (Cermets))
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