Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
5.8
3.1
Journals
Materials
Editor’s Choice
materials-logo

Journal Menu

► Journal Menu

Journal Browser

► Journal Browser
share announcement

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.

Order results
Result details
Results per page
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
24 pages, 4088 KiB  
Article
Modeling Analysis of a Polygeneration Plant Using a CeO2/Ce2O3 Chemical Looping
by Greta Magnolia, Massimo Santarelli, Domenico Ferrero and Davide Papurello
Materials 2023, 16(1), 315; https://doi.org/10.3390/ma16010315 - 29 Dec 2022
Viewed by 2598
Abstract
In the current context of complexity between climate change, environmental sustainability, resource scarcity, and geopolitical aspects of energy resources, a polygenerative system with a circular approach is considered to generate energy (thermal, electrical, and fuel), contributing to the control of CO2 emissions. [...] Read more.
In the current context of complexity between climate change, environmental sustainability, resource scarcity, and geopolitical aspects of energy resources, a polygenerative system with a circular approach is considered to generate energy (thermal, electrical, and fuel), contributing to the control of CO2 emissions. A plant for the multiple productions of electrical energy, thermal heat, DME, syngas, and methanol is discussed and analyzed, integrating a chemical cycle for CO2/H2O splitting driven using concentrated solar energy and biomethane. Two-stage chemical looping is the central part of the plant, operating with the CeO2/Ce2O3 redox couple and operating at 1.2 bar and 900 °C. The system is coupled to biomethane reforming. The chemical loop generates fuel for the plant’s secondary units: a DME synthesis and distillation unit and a solid oxide fuel cell (SOFC). The DME synthesis and distillation unit are integrated with a biomethane reforming reactor powered by concentrated solar energy to produce syngas at 800 °C. The technical feasibility in terms of performance is presented in this paper, both with and without solar irradiation, with the following results, respectively: overall efficiencies of 62.56% and 59.08%, electricity production of 6.17 MWe and 28.96 MWe, and heat production of 111.97 MWt and 35.82 MWt. The fuel production, which occurs only at high irradiance, is 0.71 kg/s methanol, 6.18 kg/s DME, and 19.68 kg/s for the syngas. The increase in plant productivity is studied by decoupling the operation of the chemical looping with a biomethane reformer from intermittent solar energy using the heat from the SOFC unit. Full article
(This article belongs to the Special Issue Sustainable Solar Energy Technologies and Materials for Solar Thermal and Power Generation)
►▼ Show Figures

Figure 1

8 pages, 2126 KiB  
Article
Macrophage Polarization Related to Biomimetic Calcium Phosphate Coatings: A Preliminary Study
by Jiping Chen, Yiwen Zhou, Xingnan Lin and Huang Li
Materials 2023, 16(1), 332; https://doi.org/10.3390/ma16010332 - 29 Dec 2022
Cited by 7 | Viewed by 2202
Abstract
Biomimetic calcium phosphate (BioCaP) coatings were used to deliver bone morphogenetic protein 2 (BMP2), and enhance osteogenesis. However, the mechanism for BioCaP coatings interacting with the immune response during bone regeneration remains unclear. In this preliminary study, the effect of BioCaP coatings on [...] Read more.
Biomimetic calcium phosphate (BioCaP) coatings were used to deliver bone morphogenetic protein 2 (BMP2), and enhance osteogenesis. However, the mechanism for BioCaP coatings interacting with the immune response during bone regeneration remains unclear. In this preliminary study, the effect of BioCaP coatings on macrophage polarization without (BioCaP group) or with BMP2 (BioCaP+Inc.BMP2 group) was investigated. RAW 264.7 cells were cultured on the rough and platelike surfaces of coatings in BioCaP and BioCaP+Inc.BMP2 groups, while cultured on smooth surfaces in the group without material for 5 days. The BioCaP coatings per se modulated the switch of M1 to M2 phenotype from day 3, which promoted the expressions of Arg1 and CD 206 but reduced the expression of TNF-α compared with No material group. To detect the microenvironmental changes, the concentrations of calcium ion (Ca2+) and inorganic phosphate (Pi), pH values, as well as calcium phosphate crystal pattern were examined. The trends of ionic environmental changes were closely related with macrophage phenotype switch. These results suggest that BioCaP coating itself may affect the macrophage polarization through surface topography, surrounding ionic environment and calcium phosphate crystal pattern. Full article
(This article belongs to the Special Issue Drug Delivery Carriers and Application of Nanomaterials)
►▼ Show Figures

Figure 1

11 pages, 4497 KiB  
Article
Facile Synthesis of Island-like ZrO2-VO2 Composite Films with Enhanced Thermochromic Performance for Smart Windows
by Jiahao Wu, Zhe Wang, Bin Li, Baoshun Liu, Xiujian Zhao, Gen Tang, Dawen Zeng and Shouqin Tian
Materials 2023, 16(1), 273; https://doi.org/10.3390/ma16010273 - 28 Dec 2022
Cited by 11 | Viewed by 2142
Abstract
VO2-based film, as a very promising thermochromic material for smart windows, has attracted extensive attention but has not been widely applied because it is difficult to simultaneously improve in terms of both solar-modulation efficiency (ΔTsol) and visible transmittance [...] Read more.
VO2-based film, as a very promising thermochromic material for smart windows, has attracted extensive attention but has not been widely applied because it is difficult to simultaneously improve in terms of both solar-modulation efficiency (ΔTsol) and visible transmittance (Tlum) when made using the magnetron-sputtering method, and it has poor durability when made using the wet chemical method. Herein, island-like ZrO2-VO2 composite films with improved thermochromic performance (ΔTsol: 12.6%, Tlum: 45.0%) were created using a simple approach combining a dual magnetron-sputtering and acid-solution procedure. The film’s ΔTsol and Tlum values were increased initially and subsequently declined as the sputtering power of the ZrO2 target was raised from 30 W to 120 W. ΔTsol achieved its maximum of 12.6% at 60 W, and Tlum reached its maximum of 51.1% at 90 W. This is likely the result of the interaction of two opposing effects: Some VO2 nanocrystals in the composite film were isolated by a few ZrO2 grains, and some pores could utilize their surface-plasmon-resonance effect at high temperature to absorb some near-infrared light for an enhanced ΔTsol and Tlum. More ZrO2 grains means fewer VO2 grains in the composite film and increased film thickness, which also results in a decrease in ΔTsol and Tlum. As a result, this work may offer a facile strategy to prepare VO2-based films with high thermochromic performance and promote their application in smart windows. Full article
(This article belongs to the Section Smart Materials)
►▼ Show Figures

Figure 1

15 pages, 2801 KiB  
Article
Tuning of the Titanium Oxide Surface to Control Magnetic Properties of Thin Iron Films
by Juliusz Chojenka, Arkadiusz Zarzycki, Marcin Perzanowski, Michał Krupiński, Tamás Fodor, Kálmán Vad and Marta Marszałek
Materials 2023, 16(1), 289; https://doi.org/10.3390/ma16010289 - 28 Dec 2022
Cited by 3 | Viewed by 2134
Abstract
We describe the magnetic properties of thin iron films deposited on the nanoporous titanium oxide templates and analyze their dependance on nanopore radius. We then compare the results to a continuous iron film of the same thickness. Additionally, we investigate the evolution of [...] Read more.
We describe the magnetic properties of thin iron films deposited on the nanoporous titanium oxide templates and analyze their dependance on nanopore radius. We then compare the results to a continuous iron film of the same thickness. Additionally, we investigate the evolution of the magnetic properties of these films after annealing. We demonstrate that the M(H) loops consist of two magnetic phases originating from the iron layer and iron oxides formed at the titanium oxide/iron interface. We perform deconvolution of hysteresis loops to extract information for each magnetic phase. Finally, we investigate the magnetic interactions between the phases and verify the presence of exchange coupling between them. We observe the altering of the magnetic properties by the nanopores as a magnetic hardening of the magnetic material. The ZFC-FC (Zero-field cooled/field cooled) measurements indicate the presence of a disordered glass state below 50 K, which can be explained by the formation of iron oxide at the titanium oxide-iron interface with a short-range magnetic order. Full article
(This article belongs to the Section Thin Films and Interfaces)
►▼ Show Figures

Graphical abstract

16 pages, 477 KiB  
Review
UV-A,B,C Emitting Persistent Luminescent Materials
by Suchinder K. Sharma, Jinu James, Shailendra Kumar Gupta and Shamima Hussain
Materials 2023, 16(1), 236; https://doi.org/10.3390/ma16010236 - 27 Dec 2022
Cited by 26 | Viewed by 3612
Abstract
The nearly dormant field of persistent luminescence has gained fresh impetus after the discovery of strontium aluminate persistent luminescence phosphor in 1996. Several efforts have been put in to prepare efficient, long decay, persistent luminescent materials which can be used for different applications. [...] Read more.
The nearly dormant field of persistent luminescence has gained fresh impetus after the discovery of strontium aluminate persistent luminescence phosphor in 1996. Several efforts have been put in to prepare efficient, long decay, persistent luminescent materials which can be used for different applications. The most explored among all are the materials which emit in the visible wavelength region, 400–650 nm, of the electromagnetic spectrum. However, since 2014, the wavelength range is extended further above 650 nm for biological applications due to easily distinguishable signal between luminescent probe and the auto-fluorescence. Recently, UV-emitting persistent materials have gained interest among researchers’ due to their possible application in information storage, phototherapy and photocatalysis. In the present review, we summarize these recent developments on the UV-emitting persistent luminescent materials to motivate young minds working in the field of luminescent materials. Full article
(This article belongs to the Special Issue Advanced Luminescent Materials and Devices)
►▼ Show Figures

Figure 1

15 pages, 4517 KiB  
Article
Investigation of PbSnTeSe High-Entropy Thermoelectric Alloy: A DFT Approach
by Ming Xia, Marie-Christine Record and Pascal Boulet
Materials 2023, 16(1), 235; https://doi.org/10.3390/ma16010235 - 27 Dec 2022
Cited by 7 | Viewed by 3616
Abstract
Thermoelectric materials have attracted extensive attention because they can directly convert waste heat into electric energy. As a brand-new method of alloying, high-entropy alloys (HEAs) have attracted much attention in the fields of materials science and engineering. Recent researches have found that HEAs [...] Read more.
Thermoelectric materials have attracted extensive attention because they can directly convert waste heat into electric energy. As a brand-new method of alloying, high-entropy alloys (HEAs) have attracted much attention in the fields of materials science and engineering. Recent researches have found that HEAs could be potentially good thermoelectric (TE) materials. In this study, special quasi-random structures (SQS) of PbSnTeSe high-entropy alloys consisting of 64 atoms have been generated. The thermoelectric transport properties of the highest-entropy PbSnTeSe-optimized structure were investigated by combining calculations from first-principles density-functional theory and on-the-fly machine learning with the semiclassical Boltzmann transport theory and Green–Kubo theory. The results demonstrate that PbSnTeSe HEA has a very low lattice thermal conductivity. The electrical conductivity, thermal electronic conductivity and Seebeck coefficient have been evaluated for both n-type and p-type doping. N-type PbSnTeSe exhibits better power factor (PF = S2σ) than p-type PbSnTeSe because of larger electrical conductivity for n-type doping. Despite high electrical thermal conductivities, the calculated ZT are satisfactory. The maximum ZT (about 1.1) is found at 500 K for n-type doping. These results confirm that PbSnTeSe HEA is a promising thermoelectric material. Full article
(This article belongs to the Special Issue Recent Advances in Thermoelectricity: Materials Processing, Characterization and Modelling)
►▼ Show Figures

Figure 1

21 pages, 5105 KiB  
Review
Metal Oxide Heterostructures for Improving Gas Sensing Properties: A Review
by Fan-Jian Meng, Rui-Feng Xin and Shan-Xin Li
Materials 2023, 16(1), 263; https://doi.org/10.3390/ma16010263 - 27 Dec 2022
Cited by 40 | Viewed by 4193
Abstract
Metal oxide semiconductor gas sensors are widely used to detect toxic and inflammable gases in industrial production and daily life. The main research hotspot in this field is the synthesis of gas sensing materials. Previous studies have shown that incorporating two or more [...] Read more.
Metal oxide semiconductor gas sensors are widely used to detect toxic and inflammable gases in industrial production and daily life. The main research hotspot in this field is the synthesis of gas sensing materials. Previous studies have shown that incorporating two or more metal oxides to form a heterojunction interface can exhibit superior gas sensing performance in response and selectivity compared with single phase. This review focuses on mainly the synthesis methods and gas sensing mechanisms of metal oxide heterostructures. A significant number of heterostructures with different morphologies and shapes have been fabricated, which exhibit specific sensing performance toward a specific target gas. Among these synthesis methods, the hydrothermal method is noteworthy due to the fabrication of diverse structures, such as nanorod-like, nanoflower-like, and hollow sphere structures with enhanced sensing properties. In addition, it should be noted that the combination of different synthesis methods is also an efficient way to obtain metal oxide heterostructures with novel morphologies. Despite advanced methods in the metal oxide semiconductors and nanotechnology field, there are still some new issues which deserve further investigation, such as long-term chemical stability of sensing materials, reproducibility of the fabrication process, and selectivity toward homogeneous gases. Moreover, the gas sensing mechanism of metal oxide heterostructures is controversial. It should be clarified so as to further integrate laboratory theory research with practical exploitation. Full article
(This article belongs to the Special Issue Advances in Dielectric Ceramics and Their Applications)
►▼ Show Figures

Figure 1

24 pages, 2755 KiB  
Article
In-Service Delaminations in FRP Structures under Operational Loading Conditions: Are Current Fracture Testing and Analysis on Coupons Sufficient for Capturing the Essential Effects for Reliable Predictions?
by Andreas J. Brunner, René Alderliesten and John-Alan Pascoe
Materials 2023, 16(1), 248; https://doi.org/10.3390/ma16010248 - 27 Dec 2022
Cited by 6 | Viewed by 2401
Abstract
Quasi-static or cyclic loading of an artificial starter crack in unidirectionally fibre-reinforced composite test coupons yields fracture mechanics data—the toughness or strain-energy release rate (labelled G)—for characterising delamination initiation and propagation. Thus far, the reproducibility of these tests is typically between 10 and [...] Read more.
Quasi-static or cyclic loading of an artificial starter crack in unidirectionally fibre-reinforced composite test coupons yields fracture mechanics data—the toughness or strain-energy release rate (labelled G)—for characterising delamination initiation and propagation. Thus far, the reproducibility of these tests is typically between 10 and 20%. However, differences in the size and possibly the shape, but also in the fibre lay-up, between test coupons and components or structures raise additional questions: Is G from a coupon test a suitable parameter for describing the behaviour of delaminations in composite structures? Can planar, two-dimensional, delamination propagation in composite plates or shells be properly predicted from essentially one-dimensional propagation in coupons? How does fibre bridging in unidirectionally reinforced test coupons relate to delamination propagation in multidirectional lay-ups of components and structures? How can multiple, localised delaminations—often created by impact in composite structures—and their interaction under service loads with constant or variable amplitudes be accounted for? Does planar delamination propagation depend on laminate thickness, thickness variation or the overall shape of the structure? How does exposure to different, variable service environments affect delamination initiation and propagation? Is the microscopic and mesoscopic morphology of FRP composite structures sufficiently understood for accurate predictive modelling and simulation of delamination behaviour? This contribution will examine selected issues and discuss the consequences for test development and analysis. The discussion indicates that current coupon testing and analysis are unlikely to provide the data for reliable long-term predictions of delamination behaviour in FRP composite structures. The attempts to make the building block design methodology for composite structures more efficient via combinations of experiments and related modelling look promising, but models require input data with low scatter and, even more importantly, insight into the physics of the microscopic damage processes yielding delamination initiation and propagation. Full article
(This article belongs to the Special Issue Damage Analysis and Reliability Assessment for Composite Materials)
►▼ Show Figures

Figure 1

16 pages, 5853 KiB  
Article
One Pot Synthesis of Copper Oxide Nanoparticles for Efficient Antibacterial Activity
by Rajaram Rajamohan, Chaitany Jayprakash Raorane, Seong-Cheol Kim and Yong Rok Lee
Materials 2023, 16(1), 217; https://doi.org/10.3390/ma16010217 - 26 Dec 2022
Cited by 28 | Viewed by 4046
Abstract
The unique semiconductor and optical properties of copper oxides have attracted researchers for decades. However, using fruit waste materials such as peels to synthesize the nanoparticles of copper oxide (CuO NPs) has been rarely described in literature reviews. The main purpose of this [...] Read more.
The unique semiconductor and optical properties of copper oxides have attracted researchers for decades. However, using fruit waste materials such as peels to synthesize the nanoparticles of copper oxide (CuO NPs) has been rarely described in literature reviews. The main purpose of this part of the research was to report on the CuO NPs with the help of apple peel extract under microwave irradiation. Metal salts and extracts were irradiated at 540 W for 5 min in a microwave in a 1:2 ratio. The crystallinity of the NPs was confirmed by the XRD patterns and the crystallite size of the NPs was found to be 41.6 nm. Elemental mapping of NPs showed homogeneous distributions of Cu and O. The NPs were found to contain Cu and O by EDX and XPS analysis. In a test involving two human pathogenic microbes, NPs showed antibacterial activity and the results revealed that the zone of inhibition grew significantly with respect to the concentration of CuO NPs. In a biofilm, more specifically, NPs at 25.0 µg/mL reduced mean thickness and biomass values of S. aureus and E. coli biofilms by >85.0 and 65.0%, respectively, with respect to untreated controls. In addition, environmentally benign materials offer a number of benefits for pharmaceuticals and other biomedical applications as they are eco-friendly and compatible. Full article
(This article belongs to the Special Issue Functionalized Nanomaterials and Structures for Biomedical Applications)
►▼ Show Figures

Graphical abstract

13 pages, 3868 KiB  
Article
Microstructural Characterization and Property of Carbon Fiber Reinforced High-Density Polyethylene Composites Fabricated by Fused Deposition Modeling
by Partha Pratim Pandit, Chang Liu, Scott Iacono, Giancarlo Corti and Yingbin Hu
Materials 2023, 16(1), 180; https://doi.org/10.3390/ma16010180 - 25 Dec 2022
Cited by 7 | Viewed by 3218
Abstract
As a promising industrial thermoplastic polymer material, high-density polyethylene (HDPE) possesses distinct properties of ease to process, good biocompatibility, high recyclability, etc. and has been widely used to make packaging, prostheses and implants, and liquid-permeable membranes. Traditional manufacturing processes for HDPE, including injection [...] Read more.
As a promising industrial thermoplastic polymer material, high-density polyethylene (HDPE) possesses distinct properties of ease to process, good biocompatibility, high recyclability, etc. and has been widely used to make packaging, prostheses and implants, and liquid-permeable membranes. Traditional manufacturing processes for HDPE, including injection molding, thermoforming, and rotational molding, require molds or post processing. In addition, part shapes are highly restricted., Thus, fused deposition modeling (FDM) is introduced to process HDPE materials to take advantage of FDM’s free of design, no mold requirement, ease and low cost of processing. To improve the mechanical properties (such as stiffness and strength) and thermal resistance of HDPE, carbon fiber (CF) was incorporated into HDPE, and CF-reinforced HDPE composites were successfully fabricated using FDM process. In addition, the effects of CF content on surface quality, microstructure characterizations, tensile properties, dynamic mechanical properties, and thermal properties have been investigated. Experimental results show that an appropriate CF content addition is beneficial for improving surface quality, and mechanical and thermal properties. Full article
(This article belongs to the Special Issue 3D Printing and Additive Manufacturing of Polymer and Composites)
►▼ Show Figures

Figure 1

22 pages, 8780 KiB  
Article
Effective Halogen-Free Flame-Retardant Additives for Crosslinked Rigid Polyisocyanurate Foams: Comparison of Chemical Structures
by Johannes U. Lenz, Doris Pospiech, Hartmut Komber, Andreas Korwitz, Oliver Kobsch, Maxime Paven, Rolf W. Albach, Martin Günther and Bernhard Schartel
Materials 2023, 16(1), 172; https://doi.org/10.3390/ma16010172 - 24 Dec 2022
Cited by 4 | Viewed by 3098
Abstract
The impact of phosphorus-containing flame retardants (FR) on rigid polyisocyanurate (PIR) foams is studied by systematic variation of the chemical structure of the FR, including non-NCO-reactive and NCO-reactive dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO)- and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-containing compounds, among them a number of compounds not reported [...] Read more.
The impact of phosphorus-containing flame retardants (FR) on rigid polyisocyanurate (PIR) foams is studied by systematic variation of the chemical structure of the FR, including non-NCO-reactive and NCO-reactive dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO)- and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-containing compounds, among them a number of compounds not reported so far. These PIR foams are compared with PIR foams without FR and with standard FRs with respect to foam properties, thermal decomposition, and fire behavior. Although BPPO and DOPO differ by just one oxygen atom, the impact on the FR properties is very significant: when the FR is a filler or a dangling (dead) end in the PIR polymer network, DOPO is more effective than BPPO. When the FR is a subunit of a diol and it is fully incorporated in the PIR network, BPPO delivers superior results. Full article
(This article belongs to the Special Issue Flame Retardants for Polymeric Materials (Second Volume))
►▼ Show Figures

Figure 1

20 pages, 9290 KiB  
Article
Polymer Composites with Self-Regulating Temperature Behavior: Properties and Characterization
by Radu Setnescu, Eduard-Marius Lungulescu and Virgil Emanuel Marinescu
Materials 2023, 16(1), 157; https://doi.org/10.3390/ma16010157 - 24 Dec 2022
Cited by 5 | Viewed by 2223
Abstract
A novel conductive composite material with homogeneous binary polymer matrix of HDPE (HD) and LLDPE (LLD), mixed with conductive filler consisting of carbon black (CB) and graphite (Gr), was tested against a HDPE composite with a similar conductive filler. Even the concentration of [...] Read more.
A novel conductive composite material with homogeneous binary polymer matrix of HDPE (HD) and LLDPE (LLD), mixed with conductive filler consisting of carbon black (CB) and graphite (Gr), was tested against a HDPE composite with a similar conductive filler. Even the concentration of the conductive filler was deliberately lower for (CB + Gr)/(LLD + HD), and the properties of this composite are comparable or better to those of (CB + Gr)/HD. The kinetic parameters of the ρ-T curves and from the DSC curves indicate that the resistivity peak is obtained when the polymer matrix is fully melted. When subjected to repeated thermal cycles, the composite (CB + Gr)/(LLD + HD) presented a better electrical behavior than composite CB + Gr)/HD, with an increase in resistivity (ρmax) values with the number of cycles, as well as less intense NTC (Negative Temperature Coefficient) effects, both for the crosslinked and thermoplastic samples. Radiation crosslinking led to increased ρmax values, as well as to inhibition of NTC effects in both cases, thus having a clear beneficial effect. Limitation effects of surface temperature and current intensity through the sample were observed at different voltages, enabling the use of these materials as self-regulating heating elements at various temperatures below the melting temperature. The procedure based on physical mixing of the components appears more efficient in imparting lower resistivity in solid state and high PTC (Positive Temperature Coefficient) effects to the composites. This effect is probably due to the concentration of the conductive particles at the surface of the polymer domains, which would facilitate the formation of the conductive paths. Further work is still necessary to optimize both the procedure of composite preparation and the properties of such materials. Full article
(This article belongs to the Special Issue Advances in Polymer Blends and Composites)
►▼ Show Figures

Figure 1

18 pages, 4962 KiB  
Article
Novel Electrospun Polycaprolactone/Calcium Alginate Scaffolds for Skin Tissue Engineering
by Maria I. Echeverria Molina, Chi-An Chen, Jeniree Martinez, Perry Tran and Kyriakos Komvopoulos
Materials 2023, 16(1), 136; https://doi.org/10.3390/ma16010136 - 23 Dec 2022
Cited by 8 | Viewed by 3018
Abstract
After decades of research, fully functional skin regeneration is still a challenge. Skin is a multilayered complex organ exhibiting a cascading healing process affected by various mechanisms. Specifically, nutrients, oxygen, and biochemical signals can lead to specific cell behavior, ultimately conducive to the [...] Read more.
After decades of research, fully functional skin regeneration is still a challenge. Skin is a multilayered complex organ exhibiting a cascading healing process affected by various mechanisms. Specifically, nutrients, oxygen, and biochemical signals can lead to specific cell behavior, ultimately conducive to the formation of high-quality tissue. This biomolecular exchange can be tuned through scaffold engineering, one of the leading fields in skin substitutes and equivalents. The principal objective of this investigation was the design, fabrication, and evaluation of a new class of three-dimensional fibrous scaffolds consisting of poly(ε-caprolactone) (PCL)/calcium alginate (CA), with the goal to induce keratinocyte differentiation through the action of calcium leaching. Scaffolds fabricated by electrospinning using a PCL/sodium alginate solution were treated by immersion in a calcium chloride solution to replace alginate-linked sodium ions by calcium ions. This treatment not only provided ion replacement, but also induced fiber crosslinking. The scaffold morphology was examined by scanning electron microscopy and systematically assessed by measurements of the pore size and the diameter, alignment, and crosslinking of the fibers. The hydrophilicity of the scaffolds was quantified by contact angle measurements and was correlated to the augmentation of cell attachment in the presence of CA. The in vitro performance of the scaffolds was investigated by seeding and staining fibroblasts and keratinocytes and using differentiation markers to detect the evolution of basal, spinous, and granular keratinocytes. The results of this study illuminate the potential of the PCL/CA scaffolds for tissue engineering and suggest that calcium leaching out from the scaffolds might have contributed to the development of a desirable biological environment for the attachment, proliferation, and differentiation of the main skin cells (i.e., fibroblasts and keratinocytes). Full article
(This article belongs to the Special Issue Advances in Biomaterials towards Tissue Engineering)
►▼ Show Figures

Figure 1

11 pages, 1388 KiB  
Article
Biomechanical Comparison of WE43-Based Magnesium vs. Titanium Miniplates in a Mandible Fracture Model in Sheep
by Heilwig Fischer, Oskar Schmidt-Bleek, Vincenzo Orassi, Dag Wulsten, Katharina Schmidt-Bleek, Max Heiland, Claudius Steffen and Carsten Rendenbach
Materials 2023, 16(1), 102; https://doi.org/10.3390/ma16010102 - 22 Dec 2022
Cited by 9 | Viewed by 2714
Abstract
In fractures of the mandible, osteosynthesis with titanium plates is considered the gold standard. Titanium is an established and reliable material, its main disadvantages being metal artefacts and the need for removal in case of osteosynthesis complications. Magnesium, as a resorbable material with [...] Read more.
In fractures of the mandible, osteosynthesis with titanium plates is considered the gold standard. Titanium is an established and reliable material, its main disadvantages being metal artefacts and the need for removal in case of osteosynthesis complications. Magnesium, as a resorbable material with an elastic modulus close to cortical bone, offers a resorbable alternative osteosynthesis material, yet mechanical studies in mandible fracture fixation are still missing. The hypothesis of this study was that magnesium miniplates show no significant difference in the mechanical integrity provided for fracture fixation in mandible fractures under load-sharing indications. In a non-inferiority test, a continuous load was applied to a sheep mandible fracture model with osteosynthesis using either titanium miniplates of 1.0 mm thickness (Ti1.0), magnesium plates of 1.75 mm (Mg1.75), or magnesium plates of 1.5 mm thickness (Mg1.5). No significant difference (p > 0.05) was found in the peak force at failure, stiffness, or force at vertical displacement of 1.0 mm between Mg1.75, Mg1.5, and Ti1.0. This study shows the non-inferiority of WE43 magnesium miniplates compared to the clinical gold standard titanium miniplates. Full article
(This article belongs to the Section Biomaterials)
►▼ Show Figures

Figure 1

17 pages, 3629 KiB  
Article
Synthesis, Structural and Magnetic Properties of Cobalt-Doped GaN Nanowires on Si by Atmospheric Pressure Chemical Vapor Deposition
by Zhe Chuan Feng, Yu-Lun Liu, Jeffrey Yiin, Li-Chyong Chen, Kuei-Hsien Chen, Benjamin Klein and Ian T. Ferguson
Materials 2023, 16(1), 97; https://doi.org/10.3390/ma16010097 - 22 Dec 2022
Cited by 3 | Viewed by 2712
Abstract
GaN nanowires (NWs) grown on silicon via atmospheric pressure chemical vapor deposition were doped with Cobalt (Co) by ion implantation, with a high dose concentration of 4 × 1016 cm−2, corresponding to an average atomic percentage of ~3.85%, and annealed [...] Read more.
GaN nanowires (NWs) grown on silicon via atmospheric pressure chemical vapor deposition were doped with Cobalt (Co) by ion implantation, with a high dose concentration of 4 × 1016 cm−2, corresponding to an average atomic percentage of ~3.85%, and annealed after the implantation. Co-doped GaN showed optimum structural properties when annealed at 700 °C for 6 min in NH3 ambience. From scanning electron microscopy, X-ray diffraction, high resolution transmission electron microscope, and energy dispersive X-ray spectroscopy measurements and analyses, the single crystalline nature of Co-GaN NWs was identified. Slight expansion in the lattice constant of Co-GaN NWs due to the implantation-induced stress effect was observed, which was recovered by thermal annealing. Co-GaN NWs exhibited ferromagnetism as per the superconducting quantum interference device (SQUID) measurement. Hysteretic curves with Hc (coercivity) of 502.5 Oe at 5 K and 201.3 Oe at 300 K were obtained. Applied with a magnetic field of 100 Oe, the transition point between paramagnetic property and ferromagnetic property was determined at 332 K. Interesting structural and conducive magnetic properties show the potential of Co-doped GaN nanowires for the next optoelectronic, electronic, spintronic, sensing, optical, and related applications. Full article
(This article belongs to the Special Issue III-V Semiconductor Optoelectronics: Materials and Devices)
►▼ Show Figures

Graphical abstract

18 pages, 4408 KiB  
Article
Solid-State Dewetting as a Driving Force for Structural Transformation and Magnetization Reversal Mechanism in FePd Thin Films
by Arkadiusz Zarzycki, Marcin Perzanowski, Michal Krupinski and Marta Marszalek
Materials 2023, 16(1), 92; https://doi.org/10.3390/ma16010092 - 22 Dec 2022
Cited by 5 | Viewed by 2195
Abstract
In this work, the process of solid-state dewetting in FePd thin films and its influence on structural transformation and magnetic properties is presented. The morphology, structure and magnetic properties of the FePd system subjected to annealing at 600 °C for different times were [...] Read more.
In this work, the process of solid-state dewetting in FePd thin films and its influence on structural transformation and magnetic properties is presented. The morphology, structure and magnetic properties of the FePd system subjected to annealing at 600 °C for different times were studied. The analysis showed a strong correlation between the dewetting process and various physical phenomena. In particular, the transition between the A1 phase and L10 phase is strongly influenced by and inextricably connected with solid-state dewetting. Major changes were observed when the film lost its continuity, including a fast growth of the L10 phase, changes in the magnetization reversal behavior or the induction of magnetic spring-like behavior. Full article
(This article belongs to the Special Issue Modeling and Characterization of Materials with Unique Magnetic, Electric and Mechanical Properties (Second Volume))
►▼ Show Figures

Figure 1

28 pages, 13676 KiB  
Article
Growth Kinetics, Microstructure Evolution, and Some Mechanical Properties of Boride Layers Produced on X165CrV12 Tool Steel
by Natalia Makuch, Michał Kulka, Mourad Keddam and Adam Piasecki
Materials 2023, 16(1), 26; https://doi.org/10.3390/ma16010026 - 21 Dec 2022
Cited by 11 | Viewed by 2141
Abstract
The powder-pack boriding technique with an open retort was used to form borided layers on X165CrV12 tool steel. The process was carried out at 1123, 1173, and 1223 K for 3, 6, and 9 h. As a result of boriding the high-chromium substrate, [...] Read more.
The powder-pack boriding technique with an open retort was used to form borided layers on X165CrV12 tool steel. The process was carried out at 1123, 1173, and 1223 K for 3, 6, and 9 h. As a result of boriding the high-chromium substrate, the produced layers consisted of three zones: an outer FeB layer, an inner Fe2B layer, and a transition zone, below which the substrate material was present. Depending on the applied parameters of boriding, the total thickness of the borided layers ranged from 12.45 to 78.76 µm. The increased temperature, as well as longer duration, was accompanied by an increase in the thickness of the FeB zone and the total layer thickness. The integral diffusion model was utilized to kinetically describe the time evolution of the thickness of the FeB and (FeB + Fe2B) layers grown on the surface of powder-pack borided X165CrV12 steel. The activation energy of boron for the FeB phase was lower than that for the Fe2B phase. This suggested that the FeB phase could be formed before the Fe2B phase appeared in the microstructure. The high chromium concentration in X165CrV12 steel led to the formation of chromium borides in the borided layer, which increased the hardness (21.88 ± 1.35 GPa for FeB zone, 17.45 ± 1.20 GPa for Fe2B zone) and Young’s modulus (386.27 ± 27.04 GPa for FeB zone, 339.75 ± 17.44 GPa for Fe2B zone). The presence of the transition zone resulted from the accumulation of chromium and carbon atoms at the interface between the tips of Fe2B needles and the substrate material. The presence of hard iron and chromium borides provided significant improvement in the wear resistance of X165CrV12 steel. The powder-pack borided steel was characterized by a four times lower mass wear intensity factor and nine times lower ratio of mass loss to the length or wear path compared to the non-borided material. Full article
(This article belongs to the Special Issue Precision and Ultra-Precision Subtractive and Additive Manufacturing Processes of Alloys and Steels)
►▼ Show Figures

Figure 1

9 pages, 4904 KiB  
Article
Theoretical Study of Dynamical and Electronic Properties of Noncentrosymmetric Superconductor NbReSi
by Surajit Basak and Andrzej Ptok
Materials 2023, 16(1), 78; https://doi.org/10.3390/ma16010078 - 21 Dec 2022
Cited by 6 | Viewed by 2444
Abstract
The noncentrosymmetric NbReSi superconductor with Tc≃6.5 K is characterized by the relatively large upper critical magnetic field. Its multigap features were observed experimentally. Recent studies suggested the realization of P6¯2m or Ima2 symmetry. We discuss the dynamical [...] Read more.
The noncentrosymmetric NbReSi superconductor with Tc≃6.5 K is characterized by the relatively large upper critical magnetic field. Its multigap features were observed experimentally. Recent studies suggested the realization of P6¯2m or Ima2 symmetry. We discuss the dynamical properties of both symmetries (e.g., phonon spectra). In this paper, using the ab initio techniques, we clarify this ambiguity, and conclude that the Ima2 symmetry is unstable, and P6¯2m should be realized. The P6¯2m symmetry is also stable in the presence of external hydrostatic pressure. We show that NbReSi with the P6¯2m symmetry should host phonon surface states for (100) and (110) surfaces. Additionally, we discuss the main electronic properties of the system with the stable symmetry. Full article
(This article belongs to the Special Issue Engineering Properties of Superconducting Materials (Second Volume))
►▼ Show Figures

Figure 1

12 pages, 3151 KiB  
Article
Nd3+, Yb3+:YF3 Optical Temperature Nanosensors Operating in the Biological Windows
by Maksim Pudovkin, Ekaterina Oleynikova, Airat Kiiamov, Mikhail Cherosov and Marat Gafurov
Materials 2023, 16(1), 39; https://doi.org/10.3390/ma16010039 - 21 Dec 2022
Cited by 9 | Viewed by 2014
Abstract
This work is devoted to the study of thermometric performances of Nd3+ (0.1 or 0.5 mol.%), Yb3+ (X%):YF3 nanoparticles. Temperature sensitivity of spectral shape is related to the phonon-assisted nature of energy transfer (PAET) between Nd3+ and Yb3+ [...] Read more.
This work is devoted to the study of thermometric performances of Nd3+ (0.1 or 0.5 mol.%), Yb3+ (X%):YF3 nanoparticles. Temperature sensitivity of spectral shape is related to the phonon-assisted nature of energy transfer (PAET) between Nd3+ and Yb3+). However, in the case of single-doped Nd3+ (0.1 or 0.5 mol.%):YF3 nanoparticles, luminescence decay time (LDT) of 4F3/2 level of Nd3+ in Nd3+ (0.5 mol.%):YF3 decreases with the temperature decrease. In turn, luminescence decay time in Nd3+ (0.1 mol.%):YF3 sample remains constant. It was proposed, that at 0.5 mol.% the cross-relaxation (CR) between Nd3+ ions takes place in contradistinction from 0.1 mol.% Nd3+ concentration. The decrease of LDT with temperature is explained by the decrease of distances between Nd3+ with temperature that leads to the increase of cross-relaxation efficiency. It was suggested, that the presence of both CR and PAET processes in the studied system (Nd3+ (0.5 mol.%), Yb3+ (X%):YF3) nanoparticles provides higher temperature sensitivity compared to the systems having one process (Nd3+ (0.1 mol.%), Yb3+ (X%):YF3). The experimental results confirmed this suggestion. The maximum relative temperature sensitivity was 0.9%·K−1 at 80 K. Full article
(This article belongs to the Collection Luminescent Materials)
►▼ Show Figures

Graphical abstract

8 pages, 2202 KiB  
Article
Deformable Photonic Crystals Based on Chiral Liquid Crystals with Thermal-Mediative Shape Memory Effect
by Min-Seok Park, Kitae Kim, Young-Joo Lee, Jun-Hee Na and Se-Um Kim
Materials 2023, 16(1), 35; https://doi.org/10.3390/ma16010035 - 21 Dec 2022
Cited by 4 | Viewed by 2087
Abstract
We propose a deformable photonic crystal that exhibits the thermal-mediative shape memory effect. The chiral liquid crystalline polymeric scaffold, which produces the structural colors from a helical twist of the liquid crystal director, is prepared through phase-stabilization of a reactive mesogen in a [...] Read more.
We propose a deformable photonic crystal that exhibits the thermal-mediative shape memory effect. The chiral liquid crystalline polymeric scaffold, which produces the structural colors from a helical twist of the liquid crystal director, is prepared through phase-stabilization of a reactive mesogen in a small molecular chiral liquid crystal (CLC), polymerization, and removal of the CLC. The prepolymer of polyurethane acrylate (PUA) is then infiltrated in the prepared scaffold and subsequently photo-polymerized to form a CLC-PUA composite film. Upon compression, this film shows the blue shift of the structural color and retains this color-shift as released from compression. As the temperature increases, the color is recovered to a pristine state. The concept proposed in this study will be useful for designing mechanochromic soft materials. Full article
(This article belongs to the Special Issue Soft Materials and Optical Devices)
►▼ Show Figures

Figure 1

18 pages, 16588 KiB  
Article
Effects of Cold Rolling Reduction on Microstructure, Thickness, Adhesive Force of Al-Si Coating and on Bending Toughness of Al-Si Coated Press-Hardened Steel
by Xue Feng, Xianlei Hu and Xianghua Liu
Materials 2023, 16(1), 4; https://doi.org/10.3390/ma16010004 - 20 Dec 2022
Viewed by 4486
Abstract
Al-Si coated press-hardened steel (PHS) is widely used along with the development of light-weight vehicles, and the tailor-rolled blank parts based on Al-Si coated PHS have attracted much attention. The preparation process includes cold rolling, austenitization, hot-stamping, and quenching. The most widely used [...] Read more.
Al-Si coated press-hardened steel (PHS) is widely used along with the development of light-weight vehicles, and the tailor-rolled blank parts based on Al-Si coated PHS have attracted much attention. The preparation process includes cold rolling, austenitization, hot-stamping, and quenching. The most widely used AS60/60 coating will change after cold rolling and austenitization, which has been little-studied. Herein, the effects of cold rolling reduction on the microstructure, thickness, adhesive force of AS60/60 coating and on bending toughness of AS60/60 coated PHS were studied. As the cold rolling reduction ratio increased from 0% to 50%, the coatings were gradually thinned, but the overall continuity was unchanged. When the reduction ratio was 40% or above, rapid diffusion channels were formed. The adhesive force of coatings was 21.50–22.15 MPa. After austenitization, the coating thickness gradually decreased as the cold rolling reduction ratio rose from 0% to 50%, but the structure and overall continuity were both unchanged, and the adhesive force was 21.60–22.40 MPa. The rapid diffusion channels promoted the transition from brittle Fe2Al5 to tough FeAl during austenitization, leading to a rapid increment in bending toughness after Al-Si coated PHS was quenched. When the reduction ratio was 50%, the bending angle was improved by 23%. Full article
(This article belongs to the Special Issue Fabrication, Characterization, and Application of Coatings and Thin Films)
►▼ Show Figures

Figure 1

21 pages, 4353 KiB  
Article
Core–Shell Fe3O4@C Nanoparticles for the Organic Dye Adsorption and Targeted Magneto-Mechanical Destruction of Ehrlich Ascites Carcinoma Cells
by Oxana S. Ivanova, Irina S. Edelman, Chun-Rong Lin, Evgeniy S. Svetlitsky, Alexey E. Sokolov, Kirill A. Lukyanenko, Alexander L. Sukhachev, Nikolay P. Shestakov, Ying-Zhen Chen and Aleksandr A. Spivakov
Materials 2023, 16(1), 23; https://doi.org/10.3390/ma16010023 - 20 Dec 2022
Cited by 9 | Viewed by 2863
Abstract
The morphology, structure, and magnetic properties of Fe3O4 and Fe3O4@C nanoparticles, as well their effectiveness for organic dye adsorption and targeted destruction of carcinoma cells, were studied. The nanoparticles exhibited a high magnetic saturation value (79.4 [...] Read more.
The morphology, structure, and magnetic properties of Fe3O4 and Fe3O4@C nanoparticles, as well their effectiveness for organic dye adsorption and targeted destruction of carcinoma cells, were studied. The nanoparticles exhibited a high magnetic saturation value (79.4 and 63.8 emu/g, correspondingly) to facilitate magnetic separation. It has been shown that surface properties play a key role in the adsorption process. Both types of organic dyes—cationic (Rhodomine C) and anionic (Congo Red and Eosine)—were well adsorbed by the Fe3O4 nanoparticles’ surface, and the adsorption process was described by the polymolecular adsorption model with a maximum adsorption capacity of 58, 22, and 14 mg/g for Congo Red, Eosine, and Rhodomine C, correspondingly. In this case, the kinetic data were described well by the pseudo-first-order model. Carbon-coated particles selectively adsorbed only cationic dyes, and the adsorption process for Methylene Blue was described by the Freundlich model, with a maximum adsorption capacity of 14 mg/g. For the case of Rhodomine C, the adsorption isotherm has a polymolecular character with a maximum adsorption capacity of 34 mg/g. To realize the targeted destruction of the carcinoma cells, the Fe3O4@C nanoparticles were functionalized with aptamers, and an experiment on the Ehrlich ascetic carcinoma cells’ destruction was carried out successively using a low-frequency alternating magnetic field. The number of cells destroyed as a result of their interaction with Fe3O4@C nanoparticles in an alternating magnetic field was 27%, compared with the number of naturally dead control cells of 6%. Full article
(This article belongs to the Special Issue Functional Nanomaterials for a Better Life)
►▼ Show Figures

Figure 1

14 pages, 5736 KiB  
Article
Structure and Thermal Stability of ε/κ-Ga2O3 Films Deposited by Liquid-Injection MOCVD
by Edmund Dobročka, Filip Gucmann, Kristína Hušeková, Peter Nádaždy, Fedor Hrubišák, Fridrich Egyenes, Alica Rosová, Miroslav Mikolášek and Milan Ťapajna
Materials 2023, 16(1), 20; https://doi.org/10.3390/ma16010020 - 20 Dec 2022
Cited by 13 | Viewed by 3405
Abstract
We report on crystal structure and thermal stability of epitaxial ε/κ-Ga2O3 thin films grown by liquid-injection metal–organic chemical vapor deposition (LI-MOCVD). Si-doped Ga2O3 films with a thickness of 120 nm and root mean square surface roughness of [...] Read more.
We report on crystal structure and thermal stability of epitaxial ε/κ-Ga2O3 thin films grown by liquid-injection metal–organic chemical vapor deposition (LI-MOCVD). Si-doped Ga2O3 films with a thickness of 120 nm and root mean square surface roughness of ~1 nm were grown using gallium-tetramethylheptanedionate (Ga(thd)3) and tetraethyl orthosilicate (TEOS) as Ga and Si precursor, respectively, on c-plane sapphire substrates at 600 °C. In particular, the possibility to discriminate between ε and κ-phase Ga2O3 using X-ray diffraction (XRD) φ-scan analysis or electron diffraction analysis using conventional TEM was investigated. It is shown that the hexagonal ε-phase can be unambiguously identified by XRD or TEM only in the case that the orthorhombic κ-phase is completely suppressed. Additionally, thermal stability of prepared ε/κ-Ga2O3 films was studied by in situ and ex situ XRD analysis and atomic force microscopy. The films were found to preserve their crystal structure at temperatures as high as 1100 °C for 5 min or annealing at 900 °C for 10 min in vacuum ambient (<1 mBar). Prolonged annealing at these temperatures led to partial transformation to β-phase Ga2O3 and possible amorphization of the films. Full article
(This article belongs to the Special Issue Wide and Ultra-Wide Bandgap Semiconductor Materials for Power Devices)
►▼ Show Figures

Figure 1

32 pages, 15538 KiB  
Review
Transparent Wood-Based Materials: Current State-of-the-Art and Future Perspectives
by Alberto Mariani and Giulio Malucelli
Materials 2022, 15(24), 9069; https://doi.org/10.3390/ma15249069 - 19 Dec 2022
Cited by 9 | Viewed by 5886
Abstract
Human history is largely characterized by the massive use of wood, the most well-known natural composite material, possessing unique thermal, mechanical, and environmental features that make it suitable for several applications, ranging from civil engineering, art, and household uses, to business uses (including [...] Read more.
Human history is largely characterized by the massive use of wood, the most well-known natural composite material, possessing unique thermal, mechanical, and environmental features that make it suitable for several applications, ranging from civil engineering, art, and household uses, to business uses (including furniture, stationery, shipbuilding, and fuel). Further, as a renewable and recyclable biomass, wood perfectly matches the current circular economy concept. However, because of its structure and composition, wood is not transparent: therefore, the possibility of removing the embedded lignin, hence limiting the light-scattering phenomena, has been investigated over the last ten to fifteen years, hence obtaining the so-called “transparent wood (TW)”. This latter represents an up-to-date key material, as it can be utilized as obtained or further functionalized, combining the transparency with other features (such as flame retardance, energy storage ability, and environmental protection, among others), which widen the potential (and practical) applications of wood. The present manuscript aims at summarizing first the current methods employed for obtaining transparent wood, and then the latest achievements concerning the properties of transparent wood, providing the reader with some perspectives about its novel functionalizations and applications. Full article
(This article belongs to the Special Issue Advanced Composite Materials: Theory, Design and Applications)
►▼ Show Figures

Figure 1

17 pages, 12813 KiB  
Article
The Influence of Co Addition on the Structure and Mechanical Properties of Tungsten Heavy Alloys
by Paweł Skoczylas and Mieczysław Kaczorowski
Materials 2022, 15(24), 9064; https://doi.org/10.3390/ma15249064 - 19 Dec 2022
Cited by 6 | Viewed by 2627
Abstract
This study shows the results of Ni replacement with Co in a W-Ni-Co-type tungsten heavy alloy (WHA) in terms of the structure and mechanical properties. Five alloys containing 92 wt. % of tungsten plus Ni and Co changing in the proportions (Co:Ni) of [...] Read more.
This study shows the results of Ni replacement with Co in a W-Ni-Co-type tungsten heavy alloy (WHA) in terms of the structure and mechanical properties. Five alloys containing 92 wt. % of tungsten plus Ni and Co changing in the proportions (Co:Ni) of 1:9, 2:8, 3:7, 4:6, and 5:5 were prepared using liquid phase sintering (LPS). The specimens were studied directly after sintering and after solution heat treatment. The tensile strength, yield strength, and elongation were evaluated. The results of tensile tests were supplemented with microhardness measurements of tungsten grains and matrix. Light microscopy was used for the microstructure, and a scanning electron microscope (SEM) equipped with an EDS attachment was applied for the assessment of the fracture mode and chemical microanalysis. It was concluded that the replacement of Ni with Co led to a tensile property increase that was accompanied by a gradual decrease in elongation that started to be critical for a Co:Ni ratio higher than 4:6. Full article
(This article belongs to the Special Issue Nonconventional Technology in Materials Processing-Volume 2)
►▼ Show Figures

Figure 1

22 pages, 3479 KiB  
Article
An Improved Optimization Model to Predict the MOR of Glulam Prepared by UF-Oxidized Starch Adhesive: A Hybrid Artificial Neural Network-Modified Genetic Algorithm Optimization Approach
by Morteza Nazerian, Jalal Karimi, Hossin Jalali Torshizi, Antonios N. Papadopoulos, Sepideh Hamedi and Elham Vatankhah
Materials 2022, 15(24), 9074; https://doi.org/10.3390/ma15249074 - 19 Dec 2022
Cited by 3 | Viewed by 2112
Abstract
The purpose of the present article is to study the bending strength of glulam prepared by plane tree (Platanus Orientalis-L) wood layers adhered by UF resin with different formaldehyde to urea molar ratios containing the modified starch adhesive with different NaOCl concentrations. Artificial [...] Read more.
The purpose of the present article is to study the bending strength of glulam prepared by plane tree (Platanus Orientalis-L) wood layers adhered by UF resin with different formaldehyde to urea molar ratios containing the modified starch adhesive with different NaOCl concentrations. Artificial neural network (ANN) as a modern tool was used to predict this response, too. The multilayer perceptron (MLP) models were used to predict the modulus of rapture (MOR) and the statistics, including the determination coefficient (R2), root mean square error (RMSE), and mean absolute percentage error (MAPE) were used to validate the prediction. Combining the ANN and the genetic algorithm by using the multiple objective and nonlinear constraint functions, the optimum point was determined based on the experimental and estimated data, respectively. The characterization analysis, performed by FTIR and XRD, was used to describe the effect of the inputs on the output. The results indicated that the statistics obtained show excellent MOR predictions by the feed-forward neural network using Levenberg–Marquardt algorithms. The comparison of the optimal output of the actual values obtained by the genetic algorithm resulting from the multi-objective function and the optimal output of the values estimated by the nonlinear constraint function indicates a minimum difference between both functions. Full article
(This article belongs to the Special Issue Sustainable Natural Materials for Engineering Application (Volume II))
►▼ Show Figures

Figure 1

16 pages, 4195 KiB  
Article
Notch Effects on the Stress Intensity Factor and on the Fatigue Crack Path for Eccentric Circular Internal Cracks in Elliptically Notched Round Bars under Tensile Loading
by Jesús Toribio, Beatriz González, Juan-Carlos Matos and Iván González
Materials 2022, 15(24), 9091; https://doi.org/10.3390/ma15249091 - 19 Dec 2022
Cited by 2 | Viewed by 2381
Abstract
In this paper, stress intensity factor (SIF) solutions are numerically obtained for notched bars subjected to tensile loading containing an eccentric circular inner crack located in the cross-section corresponding to the notch root. The finite element method and the J-integral have been [...] Read more.
In this paper, stress intensity factor (SIF) solutions are numerically obtained for notched bars subjected to tensile loading containing an eccentric circular inner crack located in the cross-section corresponding to the notch root. The finite element method and the J-integral have been used to obtain the SIF and to analyze the effect on it of three elliptical notch geometries (of equal radial depth). The results show how the SIF is greater in the notched bars than in the smooth bar and within the former when the axial semi-axis of the notch rises, its effect being greater as the diameter and eccentricity of the inner crack increase. In addition, the fatigue growth of an eccentric crack induces an increase in such eccentricity, greater as the notch axial semi-axis increases. The cause of these phenomena can be attributed to the constraint loss caused by the notch, which also facilitates bending of the specimen due to the asymmetry generated by the crack eccentricity. Full article
(This article belongs to the Special Issue Research and Modeling of Materials Fatigue and Fracture)
►▼ Show Figures

Figure 1

15 pages, 7613 KiB  
Article
Remarkable Reduction in IG with an Explicit Investigation of the Leakage Conduction Mechanisms in a Dual Surface-Modified Al2O3/SiO2 Stack Layer AlGaN/GaN MOS-HEMT
by Soumen Mazumder, Parthasarathi Pal, Kuan-Wei Lee and Yeong-Her Wang
Materials 2022, 15(24), 9067; https://doi.org/10.3390/ma15249067 - 19 Dec 2022
Cited by 6 | Viewed by 2863
Abstract
We demonstrated the performance of an Al2O3/SiO2 stack layer AlGaN/GaN metal–oxide semiconductor (MOS) high-electron-mobility transistor (HEMT) combined with a dual surface treatment that used tetramethylammonium hydroxide (TMAH) and hydrochloric acid (HCl) with post-gate annealing (PGA) modulation at 400 [...] Read more.
We demonstrated the performance of an Al2O3/SiO2 stack layer AlGaN/GaN metal–oxide semiconductor (MOS) high-electron-mobility transistor (HEMT) combined with a dual surface treatment that used tetramethylammonium hydroxide (TMAH) and hydrochloric acid (HCl) with post-gate annealing (PGA) modulation at 400 °C for 10 min. A remarkable reduction in the reverse gate leakage current (IG) up to 1.5×10−12 A/mm (@ VG = −12 V) was observed in the stack layer MOS-HEMT due to the combined treatment. The performance of the dual surface-treated MOS–HEMT was significantly improved, particularly in terms of hysteresis, gate leakage, and subthreshold characteristics, with optimized gate annealing treatment. In addition, an organized gate leakage conduction mechanism in the AlGaN/GaN MOS–HEMT with the Al2O3/SiO2 stack gate dielectric layer was investigated before and after gate annealing treatment and compared with the conventional Schottky gate. The conduction mechanism in the reverse gate bias was Poole–Frankel emission for the Schottky-gate HEMT and the MOS–HEMT before annealing. The dominant conduction mechanism was ohmic/Poole-Frankel at low/medium forward bias. Meanwhile, gate leakage was governed by the hopping conduction mechanism in the MOS–HEMT without gate annealing modulation at a higher forward bias. After post-gate annealing (PGA) treatment, however, the leakage conduction mechanism was dominated by trap-assisted tunneling at the low to medium forward bias region and by Fowler–Nordheim tunneling at the higher forward bias region. Moreover, a decent product of maximum oscillation frequency and gate length (fmax × LG) was found to reach 27.16 GHz∙µm for the stack layer MOS–HEMT with PGA modulation. The dual surface-treated Al2O3/SiO2 stack layer MOS–HEMT with PGA modulation exhibited decent performance with an IDMAX of 720 mA/mm, a peak extrinsic transconductance (GMMAX) of 120 mS/mm, a threshold voltage (VTH) of −4.8 V, a higher ION/IOFF ratio of approximately 1.2×109, a subthreshold swing of 82 mV/dec, and a cutoff frequency(ft)/maximum frequency of (fmax) of 7.5/13.58 GHz. Full article
(This article belongs to the Section Optical and Photonic Materials)
►▼ Show Figures

Figure 1

17 pages, 10100 KiB  
Article
Processing and Properties of Tungsten-Steel Composites and FGMs Prepared by Spark Plasma Sintering
by Jiří Matějíček, Radek Mušálek, Zdeněk Dlabáček, Veronika Klevarová and Lenka Kocmanová
Materials 2022, 15(24), 9037; https://doi.org/10.3390/ma15249037 - 17 Dec 2022
Cited by 2 | Viewed by 2133
Abstract
Tungsten is the prime candidate material for the plasma-facing components of fusion reactors. For the joining of tungsten armor to the cooling system or support structure, composites or graded interlayers can be used to reduce the stress concentration at the interface. These interlayers [...] Read more.
Tungsten is the prime candidate material for the plasma-facing components of fusion reactors. For the joining of tungsten armor to the cooling system or support structure, composites or graded interlayers can be used to reduce the stress concentration at the interface. These interlayers can be produced by several technologies. Among these, spark plasma sintering appears advantageous because of its ability to fabricate fully dense parts at lower temperatures and in a shorter time than traditional powder metallurgy techniques, thanks to the concurrent application of temperature, pressure, and electrical current. In this work, spark plasma sintering of tungsten-steel composites and functionally graded layers (FGMs) was investigated. As a first step, pure tungsten and steel powders of different sizes were sintered at a range of temperatures to find a suitable temperature window for fully dense compacts. Characterization of the sintered compacts included structure (by SEM); porosity (by the Archimedean method and image analysis); thermal diffusivity (by the flash method) and mechanical properties (microhardness and flexural strength). Compacts with practically full density and fine grains were obtained; while the temperature needed to achieve full sintering decreased with decreasing powder size (down to about 1500 °C for the 0.4 μm powder). For fully sintered compacts, the hardness and thermal diffusivity increased with decreasing powder size. Composites with selected tungsten/steel ratios were produced at several conditions and characterized. At temperatures of 1100 °C or above, intermetallic formation was observed in the composites; nevertheless, without a detrimental effect on the mechanical strength. Finally, the formation of graded layers and tungsten-steel joints in various configurations was demonstrated. Full article
(This article belongs to the Special Issue Advanced Technology for Materials Synthesis and Processing - Series II)
►▼ Show Figures

Figure 1

19 pages, 9321 KiB  
Article
Effective Attenuation of Electromagnetic Waves by Synergetic Effect of α-Fe2O3 and MWCNT/Graphene in LDPE-Based Composites for EMI Applications
by Praveen Manjappa, Hari Krishna Rajan, Mamatha Gowdaru Mahesh, Karthikeya Gulur Sadananda, Manjunatha Channegowda, Girish Kumar Shivashankar and Nagabhushana Bhangi Mutt
Materials 2022, 15(24), 9006; https://doi.org/10.3390/ma15249006 - 16 Dec 2022
Cited by 18 | Viewed by 2745
Abstract
In this study, a polymer nanocomposite is synthesized using magnetic and conducting fillers for enhanced electromagnetic interference (EMI) shielding. Alfa-ferrite (α-Fe2O3) nanoparticles with minimal multiwalled carbon nanotube (MWCNT) as low as 5 weight % in combination with variable concentrations [...] Read more.
In this study, a polymer nanocomposite is synthesized using magnetic and conducting fillers for enhanced electromagnetic interference (EMI) shielding. Alfa-ferrite (α-Fe2O3) nanoparticles with minimal multiwalled carbon nanotube (MWCNT) as low as 5 weight % in combination with variable concentrations of graphene nanoplatelets (GNP) are used as fillers in low-density polyethylene (LDPE) polymer matrix. Nanofillers and the polymer matrix are characterized by various techniques such as XRD, SEM, color mapping, EDAX, TGA, etc. The EMI shielding efficiency of the LDPE-based nanocomposites is tested using Vector Network Analyzer (VNA). The results showed that composite with LDPE:MWCNT:GNP:α-FO-50:5:40:5 displayed enhanced EMI shielding (in X-band (8.2–12.4 GHz) compared to other concentrations studied. This is due to the superior ohmic, dielectric, and magnetic losses at this particular composition and to the synergism amongst the filler. An attenuation of 99.99% was achieved for 5% α-Fe2O3. The mechanistic aspects of the shielding are discussed using permittivity, conductivity, and attenuation. Full article
(This article belongs to the Special Issue Facile Synthesis and Applications of Doped Metal Oxide Nanomaterials)
►▼ Show Figures

Figure 1

12 pages, 1427 KiB  
Article
Critical Current Density in d-Wave Hubbard Superconductors
by José Samuel Millán, Jorge Millán, Luis A. Pérez and Harold S. Ruiz
Materials 2022, 15(24), 8969; https://doi.org/10.3390/ma15248969 - 15 Dec 2022
Viewed by 2633
Abstract
In this work, the Generalized Hubbard Model on a square lattice is applied to evaluate the electrical current density of high critical temperature d-wave superconductors with a set of Hamiltonian parameters allowing them to reach critical temperatures close to 100 K. The [...] Read more.
In this work, the Generalized Hubbard Model on a square lattice is applied to evaluate the electrical current density of high critical temperature d-wave superconductors with a set of Hamiltonian parameters allowing them to reach critical temperatures close to 100 K. The appropriate set of Hamiltonian parameters permits us to apply our model to real materials, finding a good quantitative fit with important macroscopic superconducting properties such as the critical superconducting temperature (Tc) and the critical current density (Jc). We propose that much as in a dispersive medium, in which the velocity of electrons can be estimated by the gradient of the dispersion relation ∇ε(k), the electron velocity is proportional to ∇E(k) in the superconducting state (where E(k)=(ε(k)−μ)2+Δ2(k) is the dispersion relation of the quasiparticles, and k is the electron wave vector). This considers the change of ε(k) with respect to the chemical potential (μ) and the formation of pairs that gives rise to an excitation energy gap Δ(k) in the electron density of states across the Fermi level. When ε(k)=μ at the Fermi surface (FS), only the term for the energy gap remains, whose magnitude reflects the strength of the pairing interaction. Under these conditions, we have found that the d-wave symmetry of the pairing interaction leads to a maximum critical current density in the vicinity of the antinodal k-space direction (π,0) of approximately 1.407236×108 A/cm2, with a much greater current density along the nodal direction (π2,π2) of 2.214702×109 A/cm2. These results allow for the establishment of a maximum limit for the critical current density that could be attained by a d-wave superconductor. Full article
(This article belongs to the Special Issue Advances in Superconducting Materials: Characterization, Properties and Applications)
►▼ Show Figures

Figure 1

14 pages, 6868 KiB  
Article
Efficient Activation of Peroxymonosulfate by V-Doped Graphitic Carbon Nitride for Organic Contamination Remediation
by Zhi Deng, Zhenhua Huang, Jun Liu, Yongkui Huang and Peili Lu
Materials 2022, 15(24), 8936; https://doi.org/10.3390/ma15248936 - 14 Dec 2022
Cited by 5 | Viewed by 1753
Abstract
Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) activation have been developed as an ideal pathway for completely eradication of recalcitrant organic pollutants from water environment. Herein, the V-doped graphitic carbon nitride (g-C3N4) is rationally fabricated by one-step thermal [...] Read more.
Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) activation have been developed as an ideal pathway for completely eradication of recalcitrant organic pollutants from water environment. Herein, the V-doped graphitic carbon nitride (g-C3N4) is rationally fabricated by one-step thermal polymerization method to activate PMS for contamination decontamination. The results demonstrate the V atoms are successfully integrated into the framework of g-C3N4, which can effectively improve light absorption intensity and enhance charge separation. The V-doped g-C3N4 displays superior catalytic performance for PMS activation. Moreover, the doping content has a great influence on the activation performances. The radical quenching experiments confirm •O2−, SO4•−, and h+ are the significant species in the catalytic reaction. This work would provide a feasible strategy to exploit efficient g-C3N4-based material for PMS activation. Full article
(This article belongs to the Section Catalytic Materials)
►▼ Show Figures

Figure 1

17 pages, 3390 KiB  
Article
A Doubly Fmoc-Protected Aspartic Acid Self-Assembles into Hydrogels Suitable for Bone Tissue Engineering
by Katerina Petropoulou, Varvara Platania, Maria Chatzinikolaidou and Anna Mitraki
Materials 2022, 15(24), 8928; https://doi.org/10.3390/ma15248928 - 14 Dec 2022
Cited by 4 | Viewed by 2573
Abstract
Hydrogels have been used as scaffolds for biomineralization in tissue engineering and regenerative medicine for the repair and treatment of many tissue types. In the present work, we studied an amino acid-based material that is attached to protecting groups and self-assembles into biocompatible [...] Read more.
Hydrogels have been used as scaffolds for biomineralization in tissue engineering and regenerative medicine for the repair and treatment of many tissue types. In the present work, we studied an amino acid-based material that is attached to protecting groups and self-assembles into biocompatible and stable nanostructures that are suitable for tissue engineering applications. Specifically, the doubly protected aspartic residue (Asp) with fluorenyl methoxycarbonyl (Fmoc) protecting groups have been shown to lead to the formation of well-ordered fibrous structures. Many amino acids and small peptides which are modified with protecting groups display relatively fast self-assembly and exhibit remarkable physicochemical properties leading to three-dimensional (3D) networks, the trapping of solvent molecules, and forming hydrogels. In this study, the self-assembling fibrous structures are targeted toward calcium binding and act as nucleation points for the binding of the available phosphate groups. The cell viability, proliferation, and osteogenic differentiation of pre-osteoblastic cells cultured on the formed hydrogel under various conditions demonstrate that hydrogel formation in CaCl2 and CaCl2-Na2HPO4 solutions lead to calcium ion binding onto the hydrogels and enrichment with phosphate groups, respectively, rendering these mechanically stable hydrogels osteoinductive scaffolds for bone tissue engineering. Full article
►▼ Show Figures

Figure 1

13 pages, 2229 KiB  
Article
Shelf Life Prediction of Picric Acid via Model-Based Kinetic Analysis of Its Thermal Decomposition
by Roberto Sanchirico, Marco Luca Santonocito, Valeria Di Sarli and Luciana Lisi
Materials 2022, 15(24), 8899; https://doi.org/10.3390/ma15248899 - 13 Dec 2022
Cited by 9 | Viewed by 2175
Abstract
A priori knowledge of the shelf life of energetic materials (EMs) is relevant due to its direct association with safety and functionality. This paper proposes a quick and reliable approach to predicting the shelf life of EMs whose thermal decomposition is an autocatalytic [...] Read more.
A priori knowledge of the shelf life of energetic materials (EMs) is relevant due to its direct association with safety and functionality. This paper proposes a quick and reliable approach to predicting the shelf life of EMs whose thermal decomposition is an autocatalytic process once their failure threshold has been defined as a function of the limiting extent of conversion. This approach is based on the assumption of a kinetic law consistent with the autocatalytic behavior and on the subsequent extraction, via a suitable procedure of parameter identification, of the kinetics of thermal decomposition from differential scanning calorimetry (DSC) data gathered under dynamic conditions at three different heating rates. Its reliability is proven for picric acid (PA) through the comparison of kinetic predictions with evaluations of conversion obtained by using high performance liquid chromatography (HPLC) analysis for samples subjected to isothermal and non-isothermal accelerated aging tests, as well as for a sample of naturally aged material, i.e., PA, stored at room temperature for more than 10 years. Full article
(This article belongs to the Section Advanced Materials Characterization)
►▼ Show Figures

Figure 1

21 pages, 4659 KiB  
Article
Lignocellulosic-Based Activated Carbon-Loaded Silver Nanoparticles and Chitosan for Efficient Removal of Cadmium and Optimization Using Response Surface Methodology
by Sujata Mandal, Sreekar B. Marpu, Mohammad A. Omary, Catalin C. Dinulescu, Victor Prybutok and Sheldon Q. Shi
Materials 2022, 15(24), 8901; https://doi.org/10.3390/ma15248901 - 13 Dec 2022
Cited by 5 | Viewed by 2615
Abstract
The cadmium-contaminated water body is a worldwide concern for the environment and toxic to human beings and the removal of cadmium ions from drinking and groundwater sustainably and cost-effectively is important. A novel nano-biocomposite was obtained by impregnating silver nanoparticles (AgNPs) within kenaf-based [...] Read more.
The cadmium-contaminated water body is a worldwide concern for the environment and toxic to human beings and the removal of cadmium ions from drinking and groundwater sustainably and cost-effectively is important. A novel nano-biocomposite was obtained by impregnating silver nanoparticles (AgNPs) within kenaf-based activated carbon (KAC) in the presence of chitosan matrix (CS) by a simple, facile photoirradiation method. The nano-biocomposite (CS-KAC-Ag) was characterized by an environmental scanning electron microscope equipped with energy dispersive X-ray spectroscopy (ESEM-EDX), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) method. A Box–Behnken design of response surface methodology (RSM) was used to optimize the adsorption of Cd2+. It was found that 95.1% of Cd2+ (10 mg L−1) was eliminated at pH 9, contact time of 120 min, and adsorbent dosage of 20 mg, respectively. The adsorption of Cd2+ by CS-KAC-Ag is also in agreement with the pseudo-second-order kinetic model with an R2 (coefficient of determination) factor greater than 99%. The lab data were also corroborated by tests conducted using water samples collected from mining sites in Mexico. Along with Cd2+, the CS-KAC-Ag exhibited superior removal efficiency towards Cr6+ (91.7%) > Ni2+ (84.4%) > Co2+ (80.5%) at pH 6.5 and 0.2 g L−1 dose of the nano-adsorbent. Moreover, the adsorbent was regenerated, and the adsorption capacity remained unaltered after five successive cycles. The results showed that synthesized CS-KAC-Ag was a biocompatible and versatile porous filtering material for the decontamination of different toxic metal ions. Full article
(This article belongs to the Special Issue Materials for Heavy Metals Removal from Waters)
►▼ Show Figures

Figure 1

11 pages, 3082 KiB  
Article
Effect of Poly(vinyl alcohol) Concentration on the Micro/Mesopore Structure of SBA15 Silica
by Seongmin Kim, Minuk Jung, Seongsoo Han, Ho-Seok Jeon and Yosep Han
Materials 2022, 15(24), 8900; https://doi.org/10.3390/ma15248900 - 13 Dec 2022
Viewed by 1709
Abstract
In this work, a series of micro/mesoporous SBA15 silica materials were synthesized using P123 and poly(vinyl alcohol) (PVA) as co-templates. The pore structure of the prepared SBA15 was observed to be a function of the PVA concentration. When the amount of PVA was [...] Read more.
In this work, a series of micro/mesoporous SBA15 silica materials were synthesized using P123 and poly(vinyl alcohol) (PVA) as co-templates. The pore structure of the prepared SBA15 was observed to be a function of the PVA concentration. When the amount of PVA was relatively small, the specific surface area, micropore volume, and pore wall thickness of the synthesized SBA15 were considerably large. By contrast, when a large amount of PVA was added, the pore wall thickness was greatly reduced, but the mesopore volume and size increased. This is because the added PVA interacted with the polyethylene oxide (PEO) in the shells of the P123 micelles. Furthermore, when the amount of PVA was increased, the core polypropylene oxide (PPO) block also increased, owing to the enhanced aggregation of the P123/PVA mixed micelles. This research contributes to a basic comprehension of the cooperative interactions and formation process underlying porous silica materials, assisting in the rational design and synthesis of micro/mesoporous materials. Full article
(This article belongs to the Special Issue Recent Development of Surface Chemistry of Nanomaterials)
►▼ Show Figures

Figure 1

25 pages, 6085 KiB  
Article
Assessment of Mineralogical Characteristics of Clays and the Effect of Waste Materials on Their Index Properties for the Production of Bricks
by Aamar Danish, Ermedin Totiç, Muhammed Bayram, Mücahit Sütçü, Osman Gencel, Ertuğrul Erdoğmuş and Togay Ozbakkaloglu
Materials 2022, 15(24), 8908; https://doi.org/10.3390/ma15248908 - 13 Dec 2022
Cited by 18 | Viewed by 4113
Abstract
Significant research investigations on the characteristics of unexplored clay deposits are being conducted in light of the growing need for clay in the ceramic industry and the variable chemistry of clays. Parallel to this, the generation of waste materials like fly ash, ferrochrome [...] Read more.
Significant research investigations on the characteristics of unexplored clay deposits are being conducted in light of the growing need for clay in the ceramic industry and the variable chemistry of clays. Parallel to this, the generation of waste materials like fly ash, ferrochrome slag, and silica fume is also increasing, responsible for environmental degradation. This paper aims to study the mineralogical properties of pure clays (one specimen from Siberia and five specimens from different locations in Turkey), and the effect of mentioned waste materials on the index properties of clays obtained. This study is divided into two phases, wherein in the first phase, the pure clay specimens are analyzed against mineralogical properties (i.e., chemical composition, thermal analysis, and particle size distribution). While in the second phase, index properties of pure clay specimens and clay specimens modified with 0–50% fly ash, ferrochrome slag, and silica fume are analyzed. The results reveal that the clay specimens from Turkey (USCS classification: CL) are fit for the ceramic industry and bricks production, and incorporation of waste materials can further improve their index properties. It is also observed that incorporation of 10–30% fly ash and ferrochrome slag have higher efficiency in reducing the plasticity index of clays studied as compared to the addition of silica fume. Full article
(This article belongs to the Special Issue Environmental Impact on Mechanical Properties of Construction Materials)
►▼ Show Figures

Figure 1

26 pages, 8095 KiB  
Article
Deposition of Sol–Gel ZnO:Mg Films and Investigation of Their Structural and Optical Properties
by Tatyana Ivanova, Antoaneta Harizanova, Tatyana Koutzarova, Benedicte Vertruyen and Raphael Closset
Materials 2022, 15(24), 8883; https://doi.org/10.3390/ma15248883 - 12 Dec 2022
Cited by 18 | Viewed by 2744
Abstract
This work presents a facile sol–gel method for the deposition of ZnO and ZnO:Mg films. The films are spin coated on silicon and quartz substrates. The impact of magnesium concentrations (0, 0.5, 1, 2 and 3 wt%) and post-annealing treatments (300–600 °C) on [...] Read more.
This work presents a facile sol–gel method for the deposition of ZnO and ZnO:Mg films. The films are spin coated on silicon and quartz substrates. The impact of magnesium concentrations (0, 0.5, 1, 2 and 3 wt%) and post-annealing treatments (300–600 °C) on the film’s structural, vibrational and optical properties is investigated. Undoped ZnO films crystallize in the wurtzite phase, with crystallite sizes ranging from 9.1 nm (300 °C) to 29.7 nm (600 °C). Mg doping deteriorates the film crystallization and shifting of 002 peak towards higher diffraction angles is observed, indicating the successful incorporation of Mg into the ZnO matrix. ZnO:Mg films (2 wt%) possess the smallest crystallite size, ranging from 6.2 nm (300 °C) to 25.2 nm (600 °C). The highest Mg concentration (3 wt%) results into a segregation of the MgO phase. Lattice constants, texture coefficients and Zn–O bond lengths are discussed. The diminution of the c lattice parameter is related to the replacement of Zn2+ by Mg2+ in the ZnO host lattice. The vibrational properties are studied by Fourier transform infrared (FTIR) spectroscopy. IR lines related to Mg–O bonds are found for ZnO:Mg films with dopant concentrations of 2 and 3 wt%. The optical characterization showed that the transmittance of ZnO:Mg thin films increased from 74.5% (undoped ZnO) to about 89.1% and the optical band gap energy from 3.24 to 3.56 eV. Mg doping leads to a higher refractive index compared to undoped ZnO films. The FESEM (field emission scanning electron microscopy) technique is used for observation of the surface morphology modification of ZnO:Mg films. The doped ZnO films possess a smoother grained surface structure, opposite to the wrinkle-type morphology of undoped sol–gel ZnO films. The smoother surface leads to improved transparency of ZnO:Mg films. Full article
(This article belongs to the Special Issue Structural, Morphological, and Optical Properties of Functional Thin Films)
►▼ Show Figures

Figure 1

12 pages, 2315 KiB  
Article
Forming-Free Tunable Analog Switching in WOx/TaOx Heterojunction for Emulating Electronic Synapses
by Chandreswar Mahata, Juyeong Pyo, Beomki Jeon, Muhammad Ismail, Myounggon Kang and Sungjun Kim
Materials 2022, 15(24), 8858; https://doi.org/10.3390/ma15248858 - 12 Dec 2022
Cited by 7 | Viewed by 2159
Abstract
In this work, the sputtered deposited WOx/TaOx switching layer has been studied for resistive random-access memory (RRAM) devices. Gradual SET and RESET behaviors with reliable device-to-device variability were obtained with DC voltage sweep cycling without an electroforming process. The memristor [...] Read more.
In this work, the sputtered deposited WOx/TaOx switching layer has been studied for resistive random-access memory (RRAM) devices. Gradual SET and RESET behaviors with reliable device-to-device variability were obtained with DC voltage sweep cycling without an electroforming process. The memristor shows uniform switching characteristics, low switching voltages, and a high RON/ROFF ratio (~102). The transition from short-term plasticity (STP) to long-term potentiation (LTP) can be observed by increasing the pulse amplitude and number. Spike-rate-dependent plasticity (SRDP) and paired-pulse facilitation (PPF) learning processes were successfully emulated by sequential pulse trains. By reducing the pulse interval, the synaptic weight change increases due to the residual oxygen vacancy near the conductive filaments (CFs). This work explores mimicking the biological synaptic behavior and further development for next-generation neuromorphic applications. Full article
(This article belongs to the Section Electronic Materials)
►▼ Show Figures

Figure 1

15 pages, 5449 KiB  
Article
Deterioration of Mechanical Properties and the Damage Constitutive Model of Corroded Steel in an Industrial Environment
by Zongxing Zhang, Yuxuan Xu, Guangchong Qin, Shanhua Xu and Rou Li
Materials 2022, 15(24), 8841; https://doi.org/10.3390/ma15248841 - 11 Dec 2022
Cited by 6 | Viewed by 1750
Abstract
To investigate the degradation law of the mechanical properties of corroded steel, the standard specimens from machining steel members in service for 9 years in an industrial environment were subjected to tensile tests. The influences of different degrees and types of corrosion on [...] Read more.
To investigate the degradation law of the mechanical properties of corroded steel, the standard specimens from machining steel members in service for 9 years in an industrial environment were subjected to tensile tests. The influences of different degrees and types of corrosion on the fracture path, stress-strain curve, and mechanical properties of specimens were discussed. Finally, the damage constitutive model of corroded steel was established based on the damage mechanics theory. The results showed that the failure modes of corroded specimens were related to the degrees and types of corrosion. The fracture morphology of specimens with general corrosion were step-like and the fractures of steel were uneven. However, those with local corrosion were mainly flat-like, and the fracture path was along the cross section where the larger corrosion pits were located. The fracture path of the specimen was related to the interaction of the corroded surface and internal material defects (holes). Meanwhile, with the increase of corrosion degree, the yield platform of stress-strain curve gradually became shorter, or even disappeared, and the ultimate strain and elongation at break decreased, implying that the ductility of steel became worse. Ultimately, the good agreement between the curves of the model and test indicated that the damage model could reflect the damage development process of corroded steel in the tensile process better. Corrosion damage resulted in the decrease in the damage threshold, and the damage variable D decreased by the time fracture occurred and the maximum reduction rate was up to 62.5%. Full article
(This article belongs to the Section Corrosion)
►▼ Show Figures

Figure 1

20 pages, 36857 KiB  
Article
Use of Magnesium Silicate Contaminated with Organic Compounds in Ceramic Materials as a Pore Modifier
by Jolanta Pranckevičienė and Ina Pundienė
Materials 2022, 15(24), 8833; https://doi.org/10.3390/ma15248833 - 10 Dec 2022
Cited by 2 | Viewed by 1386
Abstract
This study investigated the use of organic compound waste (OCW) contaminated magnesium silicate/diatomite in ceramics. Substituting part of the clay (between 5 and 20 wt.%) with OCW modifies a pore structure and enhances the ceramic product’s thermal conductivity, density, and frost resistance. Prepared [...] Read more.
This study investigated the use of organic compound waste (OCW) contaminated magnesium silicate/diatomite in ceramics. Substituting part of the clay (between 5 and 20 wt.%) with OCW modifies a pore structure and enhances the ceramic product’s thermal conductivity, density, and frost resistance. Prepared samples were tested at 1000–1060 °C temperatures and their structural parameters and Maage factor, useful for frost resistance prediction, were evaluated. Results show that OCW modifies the porous structure and improves the insulating properties of the ceramic body. Increasing OCW content up to 15% in the ceramic body decreases density by up to 15.0%, and thermal conductivity by up to 42.5%, because of the modified pore structure. According to structural parameters calculation, the higher frost resistance can be predicted for ceramic bodies containing 5–10% of OCW, according to Maage factor calculation ceramic bodies containing 5–20% of OCW are frost resistant. Designed ceramic products can be attractive for use in construction due to improved energy efficiency and reduced energy consumption in buildings due to their low thermal conductivity, satisfactory mechanical strength, and sustainability based on predicted frost resistance. Full article
(This article belongs to the Section Construction and Building Materials)
►▼ Show Figures

Figure 1

11 pages, 3918 KiB  
Article
Acousto–Optic Modulation and Deflection of Terahertz Radiation
by Pavel Alekseevich Nikitin, Vasily Valerievich Gerasimov and Ildus Shevketovich Khasanov
Materials 2022, 15(24), 8836; https://doi.org/10.3390/ma15248836 - 10 Dec 2022
Cited by 4 | Viewed by 2035
Abstract
It is known that one of the ways to increase the energy efficiency of acousto–optic devices is to use ultrasound beams with a higher power density. It has been established experimentally that the use of a partially electroded ultrasonic transducer significantlyincreases the energy [...] Read more.
It is known that one of the ways to increase the energy efficiency of acousto–optic devices is to use ultrasound beams with a higher power density. It has been established experimentally that the use of a partially electroded ultrasonic transducer significantlyincreases the energy efficiency of the acousto–optic modulator of terahertz radiation. In addition, the operation of an acousto–optic deflector of terahertz radiation with the use of a sectioned ultrasound transducer was theoretically investigated. It showed that a deflector of this kind enables one to achieve higher angular resolution. Full article
(This article belongs to the Special Issue Acousto-Optical Spectral Technologies)
►▼ Show Figures

Figure 1

13 pages, 2232 KiB  
Article
High Seebeck Coefficient from Screen-Printed Colloidal PbSe Nanocrystals Thin Film
by Viviana Sousa, Guillaume Savelli, Oleg I. Lebedev, Kirill Kovnir, José H. Correia, Eliana M. F. Vieira, Pedro Alpuim and Yury V. Kolen’ko
Materials 2022, 15(24), 8805; https://doi.org/10.3390/ma15248805 - 9 Dec 2022
Cited by 6 | Viewed by 2398
Abstract
Thin-film thermoelectrics (TEs) with a thickness of a few microns present an attractive opportunity to power the internet of things (IoT). Here, we propose screen printing as an industry-relevant technology to fabricate TE thin films from colloidal PbSe quantum dots (QDs). Monodisperse 13 [...] Read more.
Thin-film thermoelectrics (TEs) with a thickness of a few microns present an attractive opportunity to power the internet of things (IoT). Here, we propose screen printing as an industry-relevant technology to fabricate TE thin films from colloidal PbSe quantum dots (QDs). Monodisperse 13 nm-sized PbSe QDs with spherical morphology were synthesized through a straightforward heating-up method. The cubic-phase PbSe QDs with homogeneous chemical composition allowed the formulation of a novel ink to fabricate 2 μm-thick thin films through robust screen printing followed by rapid annealing. A maximum Seebeck coefficient of 561 μV K−1 was obtained at 143 °C and the highest electrical conductivity of 123 S m−1 was reached at 197 °C. Power factor calculations resulted in a maximum value of 2.47 × 10−5 W m−1 K−2 at 143 °C. To the best of our knowledge, the observed Seebeck coefficient value is the highest reported for TE thin films fabricated by screen printing. Thus, this study highlights that increased Seebeck coefficients can be obtained by using QD building blocks owing to quantum confinement. Full article
(This article belongs to the Special Issue Nanostructural Thin Films: Microstructure and Optical Properties)
►▼ Show Figures

Figure 1

9 pages, 1920 KiB  
Article
Crystallographically Textured and Magnetic LaCu-Substituted Ba-Hexaferrite with Excellent Gyromagnetic Properties
by Zan Jiao, Yuantao Wang, Meng Wei, Qifan Li, Ziyu Li, Alexander S. Sokolov, Chengju Yu, Xiaona Jiang, Chuanjian Wu, Zhongwen Lan, Ke Sun, Zhong Yu and Vincent G. Harris
Materials 2022, 15(24), 8792; https://doi.org/10.3390/ma15248792 - 9 Dec 2022
Cited by 3 | Viewed by 1906
Abstract
Excellent gyromagnetic properties of textured, bulk Ba-hexaferrite samples are required for low-loss, self-biased applications for microwave and millimeter-wave (MMW) devices. However, conventionally processed bulk Ba-hexaferrite ceramics typically demonstrate low remanent magnetization values, 4πMr, of 2.0~3.0 kG, and relatively large ferromagnetic [...] Read more.
Excellent gyromagnetic properties of textured, bulk Ba-hexaferrite samples are required for low-loss, self-biased applications for microwave and millimeter-wave (MMW) devices. However, conventionally processed bulk Ba-hexaferrite ceramics typically demonstrate low remanent magnetization values, 4πMr, of 2.0~3.0 kG, and relatively large ferromagnetic resonance (FMR) linewidths, ΔHFMR, of 0.8~2 kOe. These properties lead to the development of high-performance, practical devices. Herein, crystallographically textured Ba-hexaferrite samples, of the composition Ba0.8La0.2Fe11.8Cu0.2O19, having excellent functional properties, are proposed. These materials exhibit strong anisotropy fields, Ha, of ~14.6 kOe, high remanent magnetization, 4πMr, of 3.96 kGs, and a low ΔHFMR of 401 Oe at zero-bias field at the Q-band. Concomitantly, the broadband millimeter-wave transmittance was utilized to determine the complex permeability, μ*, and permittivity, ε*, of textured hexaferrites. Based on Schlöemann’s theory of complex permeability, μ*, the remanent magnetization, 4πMr, anisotropy field, Ha, and effective linewidth, ΔHeff, were estimated; these values agree well with measured values. Full article
(This article belongs to the Special Issue Ferrites：Preparation, Micro-Structures and Properties)
►▼ Show Figures

Figure 1

10 pages, 3489 KiB  
Article
Effects of UV Absorber on Zirconia Fabricated with Digital Light Processing Additive Manufacturing
by Jin-Ho Kang, Kumaresan Sakthiabirami, Hyun-Ah Kim, Seyed Aliakbar Hosseini Toopghara, Mee-Jin Jun, Hyun-Pil Lim, Chan Park, Kwi-Dug Yun and Sang-Won Park
Materials 2022, 15(24), 8726; https://doi.org/10.3390/ma15248726 - 7 Dec 2022
Cited by 7 | Viewed by 2353
Abstract
This study evaluated the effect of UV absorbers on the dimensional accuracy of zirconia specimens fabricated by additive manufacturing using a digital light process. Zirconia suspension for additive manufacturing was prepared by setting the volume fractions (0, 0.005, 0.05, and 0.1%) of various [...] Read more.
This study evaluated the effect of UV absorbers on the dimensional accuracy of zirconia specimens fabricated by additive manufacturing using a digital light process. Zirconia suspension for additive manufacturing was prepared by setting the volume fractions (0, 0.005, 0.05, and 0.1%) of various UV absorbers. The effect of UV absorber content was evaluated through curing thickness, geometric overgrowth model design, linear deviation, and microstructure evaluation before and after sintering. Statistical analysis was performed by Kruskal–Wallis H and post-tested by the Bonferroni correction method. There was no significant difference in the cure depth according to the presence or absence of the UV absorber, the difference in geometric overgrowth was from 2.1 to 12.5%, and the overgrowth significantly decreased as the amount of added UV absorber increased. This result may contribute to improved precision of 3D multilayer ceramic products. Full article
(This article belongs to the Special Issue Zirconia and Innovative Biomaterials for Dental and Biomedical Applications)
►▼ Show Figures

Figure 1

25 pages, 5700 KiB  
Article
Nonlinear Analytical Procedure for Predicting Debonding of Laminate from Substrate Subjected to Monotonic or Cyclic Load
by Marco Lamberti, Francesco Ascione, Annalisa Napoli, Ghani Razaqpur and Roberto Realfonzo
Materials 2022, 15(23), 8690; https://doi.org/10.3390/ma15238690 - 6 Dec 2022
Cited by 6 | Viewed by 2011
Abstract
The bonding of steel/fiber-reinforced polymer (SRP/FRP) laminate strips to concrete/masonry elements has been found to be an effective and efficient technology for improving the elements’ strength and stiffness. However, premature laminate–substrate debonding is commonly observed in laboratory tests, which prevents the laminate from [...] Read more.
The bonding of steel/fiber-reinforced polymer (SRP/FRP) laminate strips to concrete/masonry elements has been found to be an effective and efficient technology for improving the elements’ strength and stiffness. However, premature laminate–substrate debonding is commonly observed in laboratory tests, which prevents the laminate from reaching its ultimate strength, and this creates uncertainty with respect to the level of strengthening that can be achieved. Therefore, for the safe and effective application of this technology, a close estimate of the debonding load is necessary. Towards this end, in this paper, a new, relatively simple, semi-analytic model is presented to determine the debonding load and the laminate stress and deformation, as well as the interfacial slip, for concrete substrates bonded to SRP/FRP and subjected to monotonic or cyclic loading. In the model, a bond-slip law with a linearly softening branch is combined with an elasto-plastic stress-strain relationship for SRP. The model results are compared with available experimental data from single-lap shear tests, with good agreement between them. Full article
(This article belongs to the Special Issue Mechanical Properties and Application of Adhesive Materials)
►▼ Show Figures

Figure 1

20 pages, 10130 KiB  
Article
Open Hole Tension of 3D Printed Aligned Discontinuous Composites
by Narongkorn Krajangsawasdi, Ian Hamerton, Benjamin K. S. Woods, Dmitry S. Ivanov and Marco L. Longana
Materials 2022, 15(23), 8698; https://doi.org/10.3390/ma15238698 - 6 Dec 2022
Cited by 5 | Viewed by 2728
Abstract
This paper explores the use of Discontinuous Aligned Fibre Filament (DcAFF), a novel discontinuous fibre reinforced thermoplastic filament for 3D printing, to produce structural complex parts. Compared to conventional composite manufacturing, 3D printing has great potential in steering fibres around small structural features. [...] Read more.
This paper explores the use of Discontinuous Aligned Fibre Filament (DcAFF), a novel discontinuous fibre reinforced thermoplastic filament for 3D printing, to produce structural complex parts. Compared to conventional composite manufacturing, 3D printing has great potential in steering fibres around small structural features. In this current study, the initial thin carbon fibre (CF)-poly(L-lactic acid) (PLA) tape, produced with the High Performance Discontinuous Fibre (HiPerDiF) technology, is now reshaped into a circular cross-section filament, the DcAFF, using a bespoke machine designed to be scalable to high production rates rather than using a labour-intensive manual moulding method as in previous work. The filaments are then fed to a general-purpose 3D printer. Tensile and open-hole tensile tests were considered in this paper for mechanical and processability of DcAFF. The 3D printed specimens fabricated with the DcAFF show superior tensile properties compared to other PLA-based 3D printed composites, even those containing continuous fibres. Curvilinear open-hole tensile test samples were fabricated to explore the processability and performances of such material in complex shapes. The mechanical performance of the produced specimens was benchmarked against conventionally laid-up specimens with a cut hole. Although the steered specimens produced have lower strength than the fully consolidated samples, the raster generated by the printing path has turned the failure mechanism of the composite from brittle to ductile. Full article
(This article belongs to the Special Issue 3D Printing and Additive Manufacturing of Polymer and Composites)
►▼ Show Figures

Figure 1

9 pages, 1620 KiB  
Article
On the Quantum Confinement Effects in Ultrathin PdO Films by Experiment and Theory
by Alexandros Barnasas, Christos S. Garoufalis, Dimitrios I. Anyfantis, Panagiotis Poulopoulos and Sotirios Baskoutas
Materials 2022, 15(23), 8700; https://doi.org/10.3390/ma15238700 - 6 Dec 2022
Cited by 2 | Viewed by 2243
Abstract
Radio frequency magnetron sputtering conducted in a high vacuum with a base pressure of 1×10−6 mbar was used to deposit ultrathin palladium films on Corning glass. The thickness of these films ranged from 0.4 to 13 nanometers. PdO films [...] Read more.
Radio frequency magnetron sputtering conducted in a high vacuum with a base pressure of 1×10−6 mbar was used to deposit ultrathin palladium films on Corning glass. The thickness of these films ranged from 0.4 to 13 nanometers. PdO films were produced after being post-annealed in a furnace at temperatures of 530 degrees Celsius in the presence of air. The results of an atomic force microscopy study showed that the material possessed a high crystalline quality with a low roughness. When looking at Tauc plots to determine the position of the direct optical band gap, the thicker films show a value that is relatively close to 2.2 eV. When the film thickness was reduced all the way down to 0.7 nm, a significant “blue shift” of more than 0.5 eV was observed. In order to provide a more in-depth understanding of the experiment, theoretical calculations based on the Hartree–Fock approximation as applied to an electron-hole system were performed in the framework of the effective mass approximation. The findings are regarded as empirical proof of the existence of quantum confinement effects. Full article
(This article belongs to the Special Issue Feature Papers in Materials Physics)
►▼ Show Figures

Figure 1

12 pages, 2681 KiB  
Article
Effective BMP-2 Release and Mineralization on a Graphene Oxide/Polyvinylpyrrolidone Hydrogel Forming Poly (ε-Caprolactone) Nanofibrous Scaffolds
by Jin-Oh Jeong, Sung-In Jeong, Youn-Mook Lim and Jong-Seok Park
Materials 2022, 15(23), 8642; https://doi.org/10.3390/ma15238642 - 4 Dec 2022
Cited by 7 | Viewed by 2408
Abstract
PCL nanofibrous scaffolds are widely used as bone scaffolds, and they can increase the efficiency of bone regeneration by loading drugs and/or growth factors onto them. However, to obtain a more effective bone regeneration effect, it is necessary to increase drug loading and [...] Read more.
PCL nanofibrous scaffolds are widely used as bone scaffolds, and they can increase the efficiency of bone regeneration by loading drugs and/or growth factors onto them. However, to obtain a more effective bone regeneration effect, it is necessary to increase drug loading and release efficiency. In this study, conductive hydrogel forming nanofibrous scaffolds were prepared to increase drug efficiency. GO has an excellent conductivity and biocompatibility, making it an efficient conductive polymer for bone differentiation. Electrospun PCL was immersed in a mixed solution of GO and PVP and then crosslinked using gamma-ray irradiation. It was confirmed that GO/PVP-PCL was successfully prepared through its characterization (morphology, thermal, chemical, electrical, and biological properties). In addition, drug-release efficiency was confirmed by electrical stimulation after loading the sample with BMP-2, a bone-regeneration growth factor. Compared to PCL, it was confirmed that GO/PVP-PCL has an approximately 20% improved drug-release efficiency and an excellent mineralization of the scaffolds using SBF. After culturing MG63 cells on GO/PVP-PCL, a high effect on osteodifferentiation was confirmed by ALP activity. Therefore, GO/PVP-PCL prepared by a gamma-ray-induced crosslinking reaction is expected to be used as biomaterial for bone-tissue engineering. Full article
(This article belongs to the Special Issue Advances in Functional Hydrogel Biomaterials)
►▼ Show Figures

Figure 1

12 pages, 8249 KiB  
Article
Bidirectional Terahertz Vortex Beam Regulator
by Jiusheng Li, Fenglei Guo, Shuping Zhang and Chao Liu
Materials 2022, 15(23), 8639; https://doi.org/10.3390/ma15238639 - 3 Dec 2022
Cited by 2 | Viewed by 2446
Abstract
Most of the reported vortex beam generators with orbital angular momentum (OAM) in the terahertz region only operate in either the reflection mode or the transmission mode, which greatly limits the integration and application in terahertz technology systems. Herein, we propose a full-space [...] Read more.
Most of the reported vortex beam generators with orbital angular momentum (OAM) in the terahertz region only operate in either the reflection mode or the transmission mode, which greatly limits the integration and application in terahertz technology systems. Herein, we propose a full-space vortex beam regulator at two different frequencies. By changing the VO2 phase transition state, the transmission and reflection mode OAM beams can be flexibly controlled by a single metasurface. For the transmission mode, the proposed structure realizes an OAM beam at the topological charges of l = 1 and 2 at 0.6 THz and 1.4 THz. For the reflection mode, our structure generates an OAM beam at the topological charges of l = 1 and 2 at 0.9 THz and 1.5 THz. Based on the superposition theorem and convolution operation principle, the regulation of an OAM vortex beam with a specific deflection angle and a symmetrical deflection OAM vortex beam are realized. The designed metasurface integrates multiple transmitted and reflected vortex beam functions in full space and has potential application in different terahertz systems. Full article
(This article belongs to the Special Issue Design and Applications of Terahertz Metamaterials)
►▼ Show Figures

Figure 1

Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying article 901-950 on page 19 of 41.
Back to TopTop