Materials

14 pages, 6711 KiB

Open AccessEditor’s ChoiceArticle

Thermal Diffusivity of Concrete Samples Assessment Using a Solar Simulator

by Marcin Bilski, Przemysław Górnaś, Andrzej Pożarycki, Przemysław Skrzypczak, Mieczysław Słowik, Marta Mielczarek, Agnieszka Wróblewska and Łukasz Semkło

Materials 2023, 16(3), 1268; https://doi.org/10.3390/ma16031268 - 2 Feb 2023

Cited by 4 | Viewed by 2067

Abstract

The thermal properties of pavement layers made of concrete with varying bulk densities are a particularly interesting topic in the context of development road technologies. If a hybrid layer system is used as a starting point, with thin asphalt layers (from 1 cm [...] Read more.

The thermal properties of pavement layers made of concrete with varying bulk densities are a particularly interesting topic in the context of development road technologies. If a hybrid layer system is used as a starting point, with thin asphalt layers (from 1 cm to 4 cm) laid on top of a foam concrete layer, thermal properties begin to play a crucial role. The main research problem was to create a test method enabling the assessment of the influence of solar heating on the thermal parameters of the building material, especially cement concrete. For this reason, this paper is concerned specifically with the assessment of a new methodology for testing and calculating the value of the thermal diffusivity coefficient of samples made of concrete varying bulk densities. In this case, using the proprietary concept the authors built a solar simulator using a multi-source lighting system. The analysis of the results of laboratory tests and numerical analyses allowed the authors to observe that there is a strong correlation between the bulk density of samples heated and the thermal diffusivity parameter, which appears in the unidirectional heat transfer equation. The strength of this relationship has been expressed with the coefficient of determination and amounts to 99%. The calculated values of the coefficient of thermal diffusivity for samples made of foam concrete range from

0.16 \times 10^{- 6}

\frac{m^{2}}{s}

to

0.52 \times 10^{- 6}

\frac{m^{2}}{s}

and are lower (from 2.5 to 8 times) than the value determined for samples made of typical cement concrete. Full article

(This article belongs to the Section Construction and Building Materials)

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15 pages, 5074 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Annealing at 500 and 900 °C on the Structure and Mechanical Properties of Al_xCoCrFeNi Alloys

by Marzena Tokarewicz, Małgorzata Grądzka-Dahlke, Katarzyna Rećko and Magdalena Łępicka

Materials 2023, 16(3), 1245; https://doi.org/10.3390/ma16031245 - 1 Feb 2023

Cited by 8 | Viewed by 2071

Abstract

The AlCoCrFeNi high-entropy alloy is sensitive to heat treatment. The aim of the present study was to test a similar correlation for Al_xCoCrFeNi alloys with less than equimolar aluminum content. This paper presents a study of the annealing effect on the [...] Read more.

The AlCoCrFeNi high-entropy alloy is sensitive to heat treatment. The aim of the present study was to test a similar correlation for Al_xCoCrFeNi alloys with less than equimolar aluminum content. This paper presents a study of the annealing effect on the structure and mechanical properties of selected alloys. Al_xCoCrFeNi alloys (x = 0, 0.5, 0.7) were fabricated by the induction melting method. The obtained specimens were annealed at 500 °C and 900 °C. A detailed study of the changes in crystalline structure due to annealing was conducted. Three-point bending and hardness tests were carried out for the as-cast and annealed specimens to determine selected mechanical properties. The study confirmed that increasing the aluminum content in the Al_xCoCrFeNi alloy improves mechanical properties. For the alloy with aluminum content x = 0.7, hardness increased by 187% and yield strength by 252% compared to the alloy without aluminum. A significant effect of annealing on the crystalline structure of the Al_0.7CoCrFeNi alloy was found, but this was not followed by changes in mechanical properties. Full article

(This article belongs to the Special Issue Advanced Materials for Multifunctional Applications)

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11 pages, 4011 KiB

Open AccessEditor’s ChoiceArticle

Short-Term Memory Characteristics of IGZO-Based Three-Terminal Devices

by Juyeong Pyo, Jong-Ho Bae, Sungjun Kim and Seongjae Cho

Materials 2023, 16(3), 1249; https://doi.org/10.3390/ma16031249 - 1 Feb 2023

Cited by 7 | Viewed by 2912

Abstract

A three-terminal synaptic transistor enables more accurate controllability over the conductance compared with traditional two-terminal synaptic devices for the synaptic devices in hardware-oriented neuromorphic systems. In this work, we fabricated IGZO-based three-terminal devices comprising HfAlO_x and CeO_x layers to demonstrate the [...] Read more.

A three-terminal synaptic transistor enables more accurate controllability over the conductance compared with traditional two-terminal synaptic devices for the synaptic devices in hardware-oriented neuromorphic systems. In this work, we fabricated IGZO-based three-terminal devices comprising HfAlO_x and CeO_x layers to demonstrate the synaptic operations. The chemical compositions and thicknesses of the devices were verified by transmission electron microscopy and energy dispersive spectroscopy in cooperation. The excitatory post-synaptic current (EPSC), paired-pulse facilitation (PPF), short-term potentiation (STP), and short-term depression (STD) of the synaptic devices were realized for the short-term memory behaviors. The IGZO-based three-terminal synaptic transistor could thus be controlled appropriately by the amplitude, width, and interval time of the pulses for implementing the neuromorphic systems. Full article

(This article belongs to the Special Issue Advances in Conducting and Semiconducting Materials)

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13 pages, 4705 KiB

Open AccessEditor’s ChoiceArticle

Freeze Drying of Polymer Nanoparticles and Liposomes Exploiting Different Saccharide-Based Approaches

by Ilaria Andreana, Valeria Bincoletto, Maela Manzoli, Francesca Rodà, Vita Giarraputo, Paola Milla, Silvia Arpicco and Barbara Stella

Materials 2023, 16(3), 1212; https://doi.org/10.3390/ma16031212 - 31 Jan 2023

Cited by 32 | Viewed by 7713

Abstract

Biodegradable nanocarriers represent promising tools for controlled drug delivery. However, one major drawback related to their use is the long-term stability, which is largely influenced by the presence of water in the formulations, so to solve this problem, freeze-drying with cryoprotectants has been [...] Read more.

Biodegradable nanocarriers represent promising tools for controlled drug delivery. However, one major drawback related to their use is the long-term stability, which is largely influenced by the presence of water in the formulations, so to solve this problem, freeze-drying with cryoprotectants has been proposed. In the present study, the influence of the freeze-drying procedure on the storage stability of poly(lactide-co-glycolide) (PLGA) nanoparticles and liposomes was evaluated. In particular, conventional cryoprotectants were added to PLGA nanoparticle and liposome formulations in various conditions. Additionally, hyaluronic acid (HA), known for its ability to target the CD44 receptor, was assessed as a cryoprotective excipient: it was added to the nanocarriers as either a free molecule or conjugated to a phospholipid to increase the interaction with the polymer or lipid matrix while exposing HA on the nanocarrier surface. The formulations were resuspended and characterized for size, polydispersity index, zeta potential and morphology. It was demonstrated that only the highest percentages of cryoprotectants allowed the resuspension of stable nanocarriers. Moreover, unlike free HA, HA-phospholipid conjugates were able to maintain the particle mean size after the reconstitution of lyophilized nanoparticles and liposomes. This study paves the way for the use of HA-phospholipids to achieve, at the same time, nanocarrier cryoprotection and active targeting. Full article

(This article belongs to the Special Issue Nanomaterials Design towards Biomedical Applications (Volume II))

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12 pages, 2797 KiB

Open AccessEditor’s ChoiceArticle

Polarization Doping in a GaN-InN System—Ab Initio Simulation

by Ashfaq Ahmad, Pawel Strak, Pawel Kempisty, Konrad Sakowski, Jacek Piechota, Yoshihiro Kangawa, Izabella Grzegory, Michal Leszczynski, Zbigniew R. Zytkiewicz, Grzegorz Muziol, Eva Monroy, Agata Kaminska and Stanislaw Krukowski

Materials 2023, 16(3), 1227; https://doi.org/10.3390/ma16031227 - 31 Jan 2023

Viewed by 2711

Abstract

Polarization doping in a GaN-InN system with a graded composition layer was studied using ab initio simulations. The electric charge volume density in the graded concentration part was determined by spatial potential dependence. The emerging graded polarization charge was determined to show that [...] Read more.

Polarization doping in a GaN-InN system with a graded composition layer was studied using ab initio simulations. The electric charge volume density in the graded concentration part was determined by spatial potential dependence. The emerging graded polarization charge was determined to show that it could be obtained from a polarization difference and the concentration slope. It was shown that the GaN-InN polarization difference is changed by piezoelectric effects. The polarization difference is in agreement with the earlier obtained data despite the relatively narrow bandgap for the simulated system. The hole generation may be applied in the design of blue and green laser and light-emitting diodes. Full article

(This article belongs to the Special Issue III-V Semiconductor Optoelectronics: Materials and Devices)

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21 pages, 5853 KiB

Open AccessEditor’s ChoiceArticle

Physicochemical Modeling of Electrochemical Impedance in Solid-State Supercapacitors

by Davood Peyrow Hedayati, Gita Singh, Michael Kucher, Tony D. Keene and Robert Böhm

Materials 2023, 16(3), 1232; https://doi.org/10.3390/ma16031232 - 31 Jan 2023

Cited by 9 | Viewed by 4236

Abstract

Solid-state supercapacitors (SSCs) consist of porous carbon electrodes and gel-polymer electrolytes and are used in novel energy storage applications. The current study aims to simulate the impedance of SSCs using a clearly defined equivalent circuit (EC) model with the ultimate goal of improving [...] Read more.

Solid-state supercapacitors (SSCs) consist of porous carbon electrodes and gel-polymer electrolytes and are used in novel energy storage applications. The current study aims to simulate the impedance of SSCs using a clearly defined equivalent circuit (EC) model with the ultimate goal of improving their performance. To this end, a conventional mathematical and a physicochemical model were adapted. The impedance was measured by electrochemical impedance spectroscopy (EIS). An EC consisting of electrical elements was introduced for each modeling approach. The mathematical model was purely based on a best-fit method and utilized an EC with intuitive elements. In contrast, the physicochemical model was motivated by advanced theories and allowed meaningful associations with properties at the electrode, the electrolyte, and their interface. The physicochemical model showed a higher approximation ability (relative error of 3.7%) due to the interface impedance integration in a more complex circuit design. However, this model required more modeling and optimization effort. Moreover, the fitted parameters differed from the analytically calculated ones due to uncertainties in the SSC’s microscale configuration, which need further investigations. Nevertheless, the results show that the proposed physicochemical model is promising in simulating EIS data of SSCs with the additional advantage of utilizing well-reasoned property-based EC elements. Full article

(This article belongs to the Special Issue New-Generation Advanced Materials for Next-Generation Supercapacitors)

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18 pages, 2394 KiB

Open AccessEditor’s ChoiceArticle

The Morphology, Mechanical and Dynamic Properties, Fire Hazard and Toxicity of Chloroprene and Butadiene Rubber Composites Cross-Linked with Zinc

by Aleksandra Smejda-Krzewicka, Przemysław Rybiński, Dariusz Bradło and Witold Żukowski

Materials 2023, 16(3), 1240; https://doi.org/10.3390/ma16031240 - 31 Jan 2023

Cited by 5 | Viewed by 2137

Abstract

This paper presents the influence of zinc on the cross-linking process, mechanical and dynamic properties, morphologies and balance of thermal degradation of blends containing chloroprene rubber (CR) and butadiene rubber (BR). The novel aspect of this research is a comprehensive approach presenting a [...] Read more.

This paper presents the influence of zinc on the cross-linking process, mechanical and dynamic properties, morphologies and balance of thermal degradation of blends containing chloroprene rubber (CR) and butadiene rubber (BR). The novel aspect of this research is a comprehensive approach presenting a new curing agent for the CR/BR blends to increase their cross-linking density and final properties, including non-flammability and low fire hazard. This is due to the need to find an alternative to zinc oxide, which is the standard curing agent for chloroprene rubber. The regulations of the European Union enforce a significant limitation on the use of this compound in elastomer technology, due to its harmful effect on aquatic organisms. In this paper, the CR/BR composites were cured with zinc and filled with natural silica fillers (sillitin or chalcedonite) or synthetic silica filler (aerosil). The investigation focused on the morphology characterization of the obtained compounds, their cross-linking degree, swelling, mechanical and dynamic properties, fire hazard and toxicity. The structure of cured CR/BR blends was characterized via scanning electron microscopy (SEM). The fire resistance studies were performed using cone calorimetry or oxygen index methods, whereas toxicity tests were performed with the use of the FB-FTIR (fluidized bed reactor coupled with FTIR analyzer) method. The results showed that obtained CR/BR products were characterized by satisfactory final properties. The properties determined by the oxygen index and cone calorimetry methods, including the behaviors of the tested CR/BR vulcanizates in fire conditions, showed that the produced compounds were characterized by a low fire hazard and can be classified as non-combustible rubber products. However, the toxicity of the decomposition products, determined at 450, 550 and 750 °C, was very high. Full article

(This article belongs to the Special Issue Morphology, Flammability, Thermal and Mechanical Properties of Polymer Composites)

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19 pages, 7258 KiB

Open AccessEditor’s ChoiceArticle

Reinforcement Corrosion Testing in Concrete and Fiber Reinforced Concrete Specimens Exposed to Aggressive External Factors

by Wioletta Raczkiewicz, Magdalena Bacharz, Kamil Bacharz and Michał Teodorczyk

Materials 2023, 16(3), 1174; https://doi.org/10.3390/ma16031174 - 30 Jan 2023

Cited by 12 | Viewed by 3394

Abstract

One of the leading causes of reinforced concrete degradation is chloride attack. It occurs due to the penetration of chlorides through pores and cracks into the concrete cover. This phenomenon becomes more dangerous if reinforced concrete elements are subjected to cyclic temperature changes. [...] Read more.

One of the leading causes of reinforced concrete degradation is chloride attack. It occurs due to the penetration of chlorides through pores and cracks into the concrete cover. This phenomenon becomes more dangerous if reinforced concrete elements are subjected to cyclic temperature changes. The concrete cover protects against corrosion. This paper presents research, the primary purpose of which was to determine the effect of the addition of steel fibers to concrete on the development of corrosion of the main reinforcement. The tests were carried out on three types of reinforced concrete specimens made of ordinary concrete and concrete with different amounts of steel fibers (0.25% and 0.50%). In order to initiate corrosion processes, specimens were partially submerged in a 3% sodium chloride solution and were subjected to freeze–thaw cycles. The electrochemical polarization galvanostatic pulse method was used for analyzing the reinforcement corrosion activity. Moreover, it was verified whether the corrosion of reinforced concrete elements affects the acoustic emission wave velocity. The addition of steel micro-reinforcement fibers increases the corrosion resistance of reinforced concrete. In addition, a strong linear correlation between the AE wave velocity and the values of the corrosion current density was revealed. Full article

(This article belongs to the Special Issue Corrosion of Materials: Evaluation, Testing, Protection, and Failure Analysis)

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14 pages, 18830 KiB

Open AccessEditor’s ChoiceArticle

MoS₂/Au Heterojunction Catalyst for SERS Monitoring of a Fenton-like Reaction

by Qian Wei, Beibei Lu, Qing Yang, Can Shi, Yulan Wei, Minmin Xu, Chenjie Zhang and Yaxian Yuan

Materials 2023, 16(3), 1169; https://doi.org/10.3390/ma16031169 - 30 Jan 2023

Cited by 1 | Viewed by 2826

Abstract

Fenton technology is one of advanced oxidation process (AOP) methods to treat wastewater through chemical oxidation. Due to the limitations of classical iron-based catalysts, it is still challenging to find suitable catalysts for Fenton-like reactions. Here, MoS₂/Au heterojunctions were successfully synthesized [...] Read more.

Fenton technology is one of advanced oxidation process (AOP) methods to treat wastewater through chemical oxidation. Due to the limitations of classical iron-based catalysts, it is still challenging to find suitable catalysts for Fenton-like reactions. Here, MoS₂/Au heterojunctions were successfully synthesized by reduction of chloroauric acid in the solution of layered MoS₂ prepared by hydrothermal method. As a model molecule, methylene blue (MB) was used as the species to be degraded to evaluate the performance of the catalyst. It was determined by UV–visible spectra that the optimal catalyst can be obtained when MoS₂ (mg): HAuCl₄ (wt. % mL) is 2:2. The Fenton-like reaction process was monitored by introducing highly sensitive surface enhanced Raman spectroscopy (SERS). The results show that MB can be degraded by 83% in the first 10 min of the reaction, indicating that MoS₂/Au has good catalytic performance. In addition, as a fingerprint spectrum, SERS was used to preliminarily analyze the molecular structure changes during the degradation process. The result showed that C-N-C bond was easier to break than the C-S-C bond. NH₂ group and the fused ring were destroyed at the comparable speed at the first 30 min. In terms of application applicability, it was showed that MB degradation had exceeded 95% at all the three pH values of 1.4, 5.0, and 11.1 after the reaction was carried out for 20 min. The test and analysis of the light environment showed that the catalytic efficiency was significantly improved in the natural light of the laboratory compared to dark conditions. The possible mechanism based on ·OH and ·O₂⁻ from ESR data was proposed. In addition, it was demonstrated to be a first-order reaction from the perspective of kinetics. This study made a positive contribution to broaden of the applicable conditions and scope of Fenton-like reaction catalysts. It is expected to be used as a non-iron catalyst in practical industrial applications. From the perspective of detection method, we expect to develop SERS as a powerful tool for the in situ monitoring of Fenton-like reactions, and to further deepen our understanding of the mechanism. Full article

(This article belongs to the Special Issue Advanced Photocatalytic Material: Synthesis, Characterization and Application)

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24 pages, 3728 KiB

Open AccessEditor’s ChoiceArticle

Effects of Altering Magnesium Metal Surfaces on Degradation In Vitro and In Vivo during Peripheral Nerve Regeneration

by Rigwed Tatu, Leon G. White, Yeoheung Yun, Tracy Hopkins, Xiaoxian An, Ahmed Ashraf, Kevin J. Little, Meir Hershcovitch, David B. Hom and Sarah Pixley

Materials 2023, 16(3), 1195; https://doi.org/10.3390/ma16031195 - 30 Jan 2023

Cited by 5 | Viewed by 3027

Abstract

In vivo use of biodegradable magnesium (Mg) metal can be plagued by too rapid a degradation rate that removes metal support before physiological function is repaired. To advance the use of Mg biomedical implants, the degradation rate may need to be adjusted. We [...] Read more.

In vivo use of biodegradable magnesium (Mg) metal can be plagued by too rapid a degradation rate that removes metal support before physiological function is repaired. To advance the use of Mg biomedical implants, the degradation rate may need to be adjusted. We previously demonstrated that pure Mg filaments used in a nerve repair scaffold were compatible with regenerating peripheral nerve tissues, reduced inflammation, and improved axonal numbers across a short—but not long—gap in sciatic nerves in rats. To determine if the repair of longer gaps would be improved by a slower Mg degradation rate, we tested, in vitro and in vivo, the effects of Mg filament polishing followed by anodization using plasma electrolytic oxidation (PEO) with non-toxic electrolytes. Polishing removed oxidation products from the surface of as-received (unpolished) filaments, exposed more Mg on the surface, produced a smoother surface, slowed in vitro Mg degradation over four weeks after immersion in a physiological solution, and improved attachment of cultured epithelial cells. In vivo, treated Mg filaments were used to repair longer (15 mm) injury gaps in adult rat sciatic nerves after placement inside hollow poly (caprolactone) nerve conduits. The addition of single Mg or control titanium filaments was compared to empty conduits (negative control) and isografts (nerves from donor rats, positive control). After six weeks in vivo, live animal imaging with micro computed tomography (micro-CT) showed that Mg metal degradation rates were slowed by polishing vs. as-received Mg, but not by anodization, which introduced greater variability. After 14 weeks in vivo, functional return was seen only with isograft controls. However, within Mg filament groups, the amount of axonal growth across the injury site was improved with slower Mg degradation rates. Thus, anodization slowed degradation in vitro but not in vivo, and degradation rates do affect nerve regeneration. Full article

(This article belongs to the Special Issue Magnesium and Its Alloys as Biodegradable Implants)

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24 pages, 5042 KiB

Open AccessEditor’s ChoiceArticle

Burdock-Derived Composites Based on Biogenic Gold, Silver Chloride and Zinc Oxide Particles as Green Multifunctional Platforms for Biomedical Applications and Environmental Protection

by Irina Zgura, Nicoleta Badea, Monica Enculescu, Valentin-Adrian Maraloiu, Camelia Ungureanu and Marcela-Elisabeta Barbinta-Patrascu

Materials 2023, 16(3), 1153; https://doi.org/10.3390/ma16031153 - 29 Jan 2023

Cited by 9 | Viewed by 3294

Abstract

Green nanotechnology is a rapidly growing field linked to using the principles of green chemistry to design novel nanomaterials with great potential in environmental and health protection. In this work, metal and semiconducting particles (AuNPs, AgClNPs, ZnO, AuZnO, AgClZnO, and AuAgClZnO) were phytosynthesized [...] Read more.

Green nanotechnology is a rapidly growing field linked to using the principles of green chemistry to design novel nanomaterials with great potential in environmental and health protection. In this work, metal and semiconducting particles (AuNPs, AgClNPs, ZnO, AuZnO, AgClZnO, and AuAgClZnO) were phytosynthesized through a “green” bottom-up approach, using burdock (Arctium lappa L.) aqueous extract. The morphological (SEM/TEM), structural (XRD, SAED), compositional (EDS), optical (UV–Vis absorption and FTIR spectroscopy), photocatalytic, and bio-properties of the prepared composites were analyzed. The particle size was determined by SEM/TEM and by DLS measurements. The phytoparticles presented high and moderate physical stability, evaluated by zeta potential measurements. The investigation of photocatalytic activity of these composites, using Rhodamine B solutions’ degradation under solar light irradiation in the presence of prepared powders, showed different degradation efficiencies. Bioevaluation of the obtained composites revealed the antioxidant and antibacterial properties. The tricomponent system AuAgClZnO showed the best antioxidant activity for capturing ROS and ABTS•⁺ radicals, and the best biocidal action against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The “green” developed composites can be considered potential adjuvants in biomedical (antioxidant or biocidal agents) or environmental (as antimicrobial agents and catalysts for degradation of water pollutants) applications. Full article

(This article belongs to the Special Issue Novel Green Nanotechnologies Applied in Environmental Protection and Health)

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16 pages, 2471 KiB

Open AccessEditor’s ChoiceArticle

Phenolic Compounds Removal from Olive Mill Wastewater Using the Composite of Activated Carbon and Copper-Based Metal-Organic Framework

by Muna A. Abu-Dalo, Nathir A. F. Al-Rawashdeh, Moath Almurabi, Jehad Abdelnabi and Abeer Al Bawab

Materials 2023, 16(3), 1159; https://doi.org/10.3390/ma16031159 - 29 Jan 2023

Cited by 9 | Viewed by 3386

Abstract

As the industry of olive oil continues to grow, the management of olive mill wastewater (OMW) by-products has become an area of great interest. While many strategies for processing OMW have been established, more studies are still required to find an effective adsorbent [...] Read more.

As the industry of olive oil continues to grow, the management of olive mill wastewater (OMW) by-products has become an area of great interest. While many strategies for processing OMW have been established, more studies are still required to find an effective adsorbent for total phenolic content uptake. Here, we present a composite of a Cu 1,4-benzene dicarboxylate metal-organic framework (Cu (BDC) MOF) and granular activated carbon (GAC) as an adsorbent for total phenolic content removal from OMW. Experimental results demonstrated that the maximum adsorption capacity was 20 mg/g of total phenolic content (TPC) after 4 h. using 2% wt/wt of GAC/Cu (BDC) MOF composite to OMW at optimum conditions (pH of 4.0 and 25 °C). The adsorption of phenolic content onto the GAC/Cu (BDC) MOF composite was described by the Freundlich adsorption and pseudo-second-order reaction. The adsorption reaction was found to be spontaneous and endothermic at 298 K where ΔS° and ΔH° were found to be 0.105 KJ/mol and 25.7 kJ/mol, respectively. While ΔGº value was −5.74 (kJ/mol). The results of this study provide a potential solution for the local and worldwide olive oil industry. Full article

(This article belongs to the Special Issue Recent Progress in Advanced Adsorption Materials)

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15 pages, 3009 KiB

Open AccessEditor’s ChoiceArticle

ZGSO Spinel Nanoparticles with Dual Emission of NIR Persistent Luminescence for Anti-Counterfeiting Applications

by Guanyu Cai, Teresa Delgado, Cyrille Richard and Bruno Viana

Materials 2023, 16(3), 1132; https://doi.org/10.3390/ma16031132 - 28 Jan 2023

Cited by 35 | Viewed by 4442

Abstract

The property of persistent luminescence shows great potential for anti-counterfeiting technology and imaging by taking advantage of a background-free signal. Current anti-counterfeiting technologies face the challenge of low security and the inconvenience of being limited to visible light emission, as emitters in the [...] Read more.

The property of persistent luminescence shows great potential for anti-counterfeiting technology and imaging by taking advantage of a background-free signal. Current anti-counterfeiting technologies face the challenge of low security and the inconvenience of being limited to visible light emission, as emitters in the NIR optical windows are required for such applications. Here, we report the preparation of a series of Zn_1+xGa_2−2xSn_xO₄ nanoparticles (ZGSO NPs) with persistent luminescence in the first and second near-infrared window to overcome these challenges. ZGSO NPs, doped with transition-metal (Cr³⁺ and/or Ni²⁺) and in some cases co-doped with rare-earth (Er³⁺) ions, were successfully prepared using an improved solid-state method with a subsequent milling process to reach sub-200 nm size particles. X-ray diffraction and absorption spectroscopy were used for the analysis of the structure and local crystal field around the dopant ions at different Sn⁴⁺/Ga³⁺ ratios. The size of the NPs was ~150 nm, measured by DLS. Doped ZGSO NPs exhibited intense photoluminescence in the range from red, NIR-I to NIR-II, and even NIR-III, under UV radiation, and showed persistent luminescence at 700 nm (NIR-I) and 1300 nm (NIR-II) after excitation removal. Hence, these NPs were evaluated for multi-level anti-counterfeiting technology. Full article

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

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17 pages, 10804 KiB

Open AccessEditor’s ChoiceArticle

Effect of Polydopamine Coating of Cellulose Nanocrystals on Performance of PCL/PLA Bio-Nanocomposites

by Ivan Kelnar, Ludmila Kaprálková, Sabina Krejčíková, Jiří Dybal, Michaela Vyroubalová and A. M. Abdel-Mohsen

Materials 2023, 16(3), 1087; https://doi.org/10.3390/ma16031087 - 27 Jan 2023

Cited by 4 | Viewed by 2486

Abstract

In bio-nanocomposites with a poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) matrix with neat and polydopamine (PDA)-coated cellulose nanocrystals (CNCd), the use of different mixing protocols with masterbatches prepared by solution casting led to marked variation of localization, as well as reinforcing and structure-directing effects, of [...] Read more.

In bio-nanocomposites with a poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) matrix with neat and polydopamine (PDA)-coated cellulose nanocrystals (CNCd), the use of different mixing protocols with masterbatches prepared by solution casting led to marked variation of localization, as well as reinforcing and structure-directing effects, of cellulose nanocrystals (CNC). The most balanced mechanical properties were found with an 80/20 PLA/PCL ratio, and complex PCL/CNC structures were formed. In the nanocomposites with a bicontinuous structure (60/40 and 40/60 PLA/PCL ratios), pre-blending the CNC and CNCd/PLA caused a marked increase in the continuity of mechanically stronger PLA and an improvement in related parameters of the system. On the other hand, improved continuity of the PCL phase when using a PCL masterbatch may lead to the reduction in or elimination of reinforcing effects. The PDA coating of CNC significantly changed its behavior. In particular, a higher affinity to PCL and ordering of PLA led to dissimilar structures and interface transformations, while also having antagonistic effects on mechanical properties. The negligible differences in bulk crystallinity indicate that alteration of mechanical properties may have originated from differences in crystallinity at the interface, also influenced by presence of CNC in this area. The complex effect of CNC on bio-nanocomposites, including the potential of PDA coating to increase thermal stability, is worthy of further study. Full article

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

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14 pages, 3616 KiB

Open AccessEditor’s ChoiceArticle

Raclopride-Molecularly Imprinted Polymers: A Promising Technology for Selective [¹¹C]Raclopride Purification

by Roberta Del Sole, Giancarlo Pascali, Giuseppe Mele, Gary Perkins and Lucia Mergola

Materials 2023, 16(3), 1091; https://doi.org/10.3390/ma16031091 - 27 Jan 2023

Viewed by 1876

Abstract

In this work, we developed a novel approach to purify [¹¹C]Raclopride ([¹¹C]RAC), an important positron emission tomography radiotracer, based on tailored shape-recognition polymers, with the aim to substitute single-pass HPLC purification with an in-flow trap & release process. Molecular [...] Read more.

In this work, we developed a novel approach to purify [¹¹C]Raclopride ([¹¹C]RAC), an important positron emission tomography radiotracer, based on tailored shape-recognition polymers, with the aim to substitute single-pass HPLC purification with an in-flow trap & release process. Molecular imprinting technology (MIT) applied to solid phase extraction (MISPE) was investigated to develop a setting able to selectively extract [¹¹C]RAC in a mixture containing a high amount of its precursor, (S)-O-Des-Methyl-Raclopride (DM-RAC). Two imprinted polymers selective for unlabeled RAC and DM-RAC were synthesized through a radical polymerization at 65 °C using methacrylic acid and trimethylolpropane trimethacrylate in the presence of template molecule (RAC or DM-RAC). The prepared polymer was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy and tested in MISPE experiments. The polymers were used in testing conditions, revealing a high retention capacity of RAC-MISPE to retain RAC either in the presence of similar concentrations of RAC and DM-RAC precursor (96.9%, RSD 6.6%) and in the presence of a large excess of precursor (90%, RSD 4.6%) in the loading solution. Starting from these promising results, preliminary studies for selective purification of [¹¹C]Raclopride using this RAC-MISPE were performed and, while generally confirming the selectivity capacity of the polymer, revealed challenging applicability to the current synthetic process, mainly due to high backpressures and long elution times. Full article

(This article belongs to the Section Materials Chemistry)

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13 pages, 2416 KiB

Open AccessEditor’s ChoiceArticle

Carbon Quantum Dots Accelerating Surface Charge Transfer of 3D PbBiO₂I Microspheres with Enhanced Broad Spectrum Photocatalytic Activity—Development and Mechanism Insight

by Ruyu Yan, Xinyi Liu, Haijie Zhang, Meng Ye, Zhenxing Wang, Jianjian Yi, Binxian Gu and Qingsong Hu

Materials 2023, 16(3), 1111; https://doi.org/10.3390/ma16031111 - 27 Jan 2023

Cited by 5 | Viewed by 2787

Abstract

The development of a highly efficient, visible-light responsive catalyst for environment purification has been a long-standing exploit, with obstacles to overcome, including inefficient capture of near-infrared photons, undesirable recombination of photo-generated carriers, and insufficient accessible reaction sites. Hence, novel carbon quantum dots (CQDs) [...] Read more.

The development of a highly efficient, visible-light responsive catalyst for environment purification has been a long-standing exploit, with obstacles to overcome, including inefficient capture of near-infrared photons, undesirable recombination of photo-generated carriers, and insufficient accessible reaction sites. Hence, novel carbon quantum dots (CQDs) modified PbBiO₂I photocatalyst were synthesized for the first time through an in-situ ionic liquid-induced method. The bridging function of 1-butyl-3-methylimidazolium iodide ([Bmim]I) guarantees the even dispersion of CQDs around PbBiO₂I surface, for synchronically overcoming the above drawbacks and markedly promoting the degradation efficiency of organic contaminants: (i) CQDs decoration harness solar photons in the near-infrared region; (ii) particular delocalized conjugated construction of CQDs strength via the utilization of photo-induced carriers; (iii) π–π interactions increase the contact between catalyst and organic molecules. Benefiting from these distinguished features, the optimized CQDs/PbBiO₂I nanocomposite displays significantly enhanced photocatalytic performance towards the elimination of rhodamine B and ciprofloxacin under visible/near-infrared light irradiation. The spin-trapping ESR analysis demonstrates that CQDs modification can boost the concentration of reactive oxygen species (O₂^•−). Combined with radicals trapping tests, valence-band spectra, and Mott–Schottky results, a possible photocatalytic mechanism is proposed. This work establishes a significant milestone in constructing CQDs-modified, bismuth-based catalysts for solar energy conversion applications. Full article

(This article belongs to the Special Issue Advanced Photocatalytic Materials for Environmental and Energy Applications)

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10 pages, 20760 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Optical and Electronic Properties of Silicon Nanosheets by Phosphorus Doping Passivation

by Ye Lei, Deren Yang and Dongsheng Li

Materials 2023, 16(3), 1079; https://doi.org/10.3390/ma16031079 - 26 Jan 2023

Cited by 3 | Viewed by 2299

Abstract

In this paper, we use the spin-on-dopant technique for phosphorus doping to improve the photoelectric properties of soft-chemical-prepared silicon nanosheets. It was found that the luminescence intensity and luminescence lifetime of the doped samples was approximately 4 fold that of the undoped samples, [...] Read more.

In this paper, we use the spin-on-dopant technique for phosphorus doping to improve the photoelectric properties of soft-chemical-prepared silicon nanosheets. It was found that the luminescence intensity and luminescence lifetime of the doped samples was approximately 4 fold that of the undoped samples, due to passivation of the surface defects by phosphorus doping. Meanwhile, phosphorus doping combined with high-temperature heat treatment can reduce the resistivity of multilayer silicon nanosheets by 6 fold compared with that of as-prepared samples. In conclusion, our work brings soft-chemical-prepared silicon nanosheets one step closer to practical application in the field of optoelectronics. Full article

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

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12 pages, 6387 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Surface Properties of the Al_0.65CoCrFeNi High-Entropy Alloy via Laser Remelting

by Junwei Miao, Tianxin Li, Qiang Li, Xiaohu Chen, Zheng Ren and Yiping Lu

Materials 2023, 16(3), 1085; https://doi.org/10.3390/ma16031085 - 26 Jan 2023

Cited by 16 | Viewed by 2415

Abstract

The laser remelting technique was applied to the surface modification of the Al_0.65CoCrFeNi high-entropy alloy (HEA) to further advance its mechanical potential. The microstructure of the remelted layer was refined from coarse dendritic to submicron-scale basket weave compared with the as-cast [...] Read more.

The laser remelting technique was applied to the surface modification of the Al_0.65CoCrFeNi high-entropy alloy (HEA) to further advance its mechanical potential. The microstructure of the remelted layer was refined from coarse dendritic to submicron-scale basket weave compared with the as-cast substrate, resulting in a 1.8-time increase in Vickers microhardness. The nanoindentation tests indicated that the nanohardness of the remelted layer was higher than that of each phase in the substrate. Meanwhile, the remelted layer retained considerable plasticity, as evidenced by its high W_p/W_t ratio (0.763) and strain hardening exponent (0.302). Additionally, adhesive wear prevailed on the substrate, while only abrasive wear features were observed on the remelted layer. Accordingly, the average friction coefficient and the wear rate of the remelted layer were minimized by 23% and 80%, respectively, compared with the substrate. Our findings explored an industrialized method to enhance the surface properties of the Al_0.65CoCrFeNi HEA and also provided some helpful references for its laser additive manufacturing. Full article

(This article belongs to the Special Issue New Functional Materials with Cavitation-Erosion Resistance)

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29 pages, 3912 KiB

Open AccessEditor’s ChoiceReview

Ongoing Challenges of Laser-Based Powder Bed Fusion Processing of Al Alloys and Potential Solutions from the Literature—A Review

by Alessandra Martucci, Alberta Aversa and Mariangela Lombardi

Materials 2023, 16(3), 1084; https://doi.org/10.3390/ma16031084 - 26 Jan 2023

Cited by 39 | Viewed by 6903

Abstract

Their high strength-to-weight ratio, good corrosion resistance and excellent thermal and electrical conductivity have exponentially increased the interest in aluminium alloys in the context of laser-based powder bed fusion (PBF-LB/M) production. Although Al-based alloys are the third most investigated category of alloys in [...] Read more.

Their high strength-to-weight ratio, good corrosion resistance and excellent thermal and electrical conductivity have exponentially increased the interest in aluminium alloys in the context of laser-based powder bed fusion (PBF-LB/M) production. Although Al-based alloys are the third most investigated category of alloys in the literature and the second most used in industry, their processing by PBF-LB/M is often hampered by their considerable solidification shrinkage, tendency to oxidation, high laser reflectivity and poor powder flowability. For these reasons, high-strength Al-based alloys traditionally processed by conventional procedures have often proved to be unprintable with additive technology, so the design and development of new tailored Al-based alloys for PBF-LB/M production is necessary. The aim of the present work is to explore all the challenges encountered before, during and after the PBF-LB/M processing of Al-based alloys, in order to critically analyse the solutions proposed in the literature and suggest new approaches for addressing unsolved problems. The analysis covers the critical aspects in the literature as well as industrial needs, industrial patents published to date and possible future developments in the additive market. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Laser Additive Manufactured Metals II)

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18 pages, 3615 KiB

Open AccessEditor’s ChoiceReview

Research Progress on Multi-Component Alloying and Heat Treatment of High Strength and Toughness Al–Si–Cu–Mg Cast Aluminum Alloys

by Mingshan Zhang, Yaqiang Tian, Xiaoping Zheng, Yuan Zhang, Liansheng Chen and Junsheng Wang

Materials 2023, 16(3), 1065; https://doi.org/10.3390/ma16031065 - 25 Jan 2023

Cited by 44 | Viewed by 5144

Abstract

Al–Si–Cu–Mg cast aluminum alloys have important applications in automobile lightweight due to their advantages such as high strength-to-weight ratio, good heat resistance and excellent casting performance. With the increasing demand for strength and toughness of automotive parts, the development of high strength and [...] Read more.

Al–Si–Cu–Mg cast aluminum alloys have important applications in automobile lightweight due to their advantages such as high strength-to-weight ratio, good heat resistance and excellent casting performance. With the increasing demand for strength and toughness of automotive parts, the development of high strength and toughness Al–Si–Cu–Mg cast aluminum alloys is one of the effective measures to promote the application of cast aluminum alloys in the automotive industry. In this paper, the research progress of improving the strength and toughness of Al–Si–Cu–Mg cast aluminum alloys was described from the aspects of multi-component alloying and heat treatment based on the strengthening mechanism of Al–Si–Cu–Mg cast aluminum alloys. Finally, the development prospects of automotive lightweight Al–Si–Cu–Mg cast aluminum alloys is presented. Full article

(This article belongs to the Special Issue Heat Treatments and Performance of Alloy and Metal)

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16 pages, 5120 KiB

Open AccessEditor’s ChoiceArticle

Nanolithographic Fabrication Technologies for Network-Based Biocomputation Devices

by Christoph R. Meinecke, Georg Heldt, Thomas Blaudeck, Frida W. Lindberg, Falco C. M. J. M. van Delft, Mohammad Ashikur Rahman, Aseem Salhotra, Alf Månsson, Heiner Linke, Till Korten, Stefan Diez, Danny Reuter and Stefan E. Schulz

Materials 2023, 16(3), 1046; https://doi.org/10.3390/ma16031046 - 24 Jan 2023

Cited by 4 | Viewed by 2559

Abstract

Network-based biocomputation (NBC) relies on accurate guiding of biological agents through nanofabricated channels produced by lithographic patterning techniques. Here, we report on the large-scale, wafer-level fabrication of optimized microfluidic channel networks (NBC networks) using electron-beam lithography as the central method. To confirm the [...] Read more.

Network-based biocomputation (NBC) relies on accurate guiding of biological agents through nanofabricated channels produced by lithographic patterning techniques. Here, we report on the large-scale, wafer-level fabrication of optimized microfluidic channel networks (NBC networks) using electron-beam lithography as the central method. To confirm the functionality of these NBC networks, we solve an instance of a classical non-deterministic-polynomial-time complete (“NP-complete”) problem, the subset-sum problem. The propagation of cytoskeletal filaments, e.g., molecular motor-propelled microtubules or actin filaments, relies on a combination of physical and chemical guiding along the channels of an NBC network. Therefore, the nanofabricated channels have to fulfill specific requirements with respect to the biochemical treatment as well as the geometrical confienement, with walls surrounding the floors where functional molecular motors attach. We show how the material stack used for the NBC network can be optimized so that the motor-proteins attach themselves in functional form only to the floor of the channels. Further optimizations in the nanolithographic fabrication processes greatly improve the smoothness of the channel walls and floors, while optimizations in motor-protein expression and purification improve the activity of the motor proteins, and therefore, the motility of the filaments. Together, these optimizations provide us with the opportunity to increase the reliability of our NBC devices. In the future, we expect that these nanolithographic fabrication technologies will enable production of large-scale NBC networks intended to solve substantially larger combinatorial problems that are currently outside the capabilities of conventional software-based solvers. Full article

(This article belongs to the Special Issue Lithography: Materials, Processes and Applications)

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13 pages, 5967 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of the Influence of Grain Sizes of Nanostructured WO₃ Ceramics on the Resistance to Radiation-Induced Softening

by Dauren B. Kadyrzhanov, Artem L. Kozlovskiy, Maxim V. Zdorovets, Inesh E. Kenzhina and Dmitriy I. Shlimas

Materials 2023, 16(3), 1028; https://doi.org/10.3390/ma16031028 - 23 Jan 2023

Cited by 2 | Viewed by 1814

Abstract

The main purpose of this study is to test a hypothesis about the effect of grain size on the resistance to destruction and changes in the strength and mechanical properties of oxide ceramics subjected to irradiation. WO₃ powders were chosen as objects [...] Read more.

The main purpose of this study is to test a hypothesis about the effect of grain size on the resistance to destruction and changes in the strength and mechanical properties of oxide ceramics subjected to irradiation. WO₃ powders were chosen as objects of study, which have a number of unique properties that meet the requirements for their use as a basis for inert matrices of dispersed nuclear fuel. The grain-size variation in WO₃ ceramics was investigated by mechanochemical grinding of powders with different grinding speeds. Grinding conditions were experimentally selected to obtain powders with a high degree of size homogeneity, which were used for further research. During evaluation of the strength properties, it was found that a decrease in the grain size leads to an increase in the crack resistance, as well as the hardness of ceramics. The increase in strength properties can be explained by an increase in the dislocation density and the volume contribution of grain boundaries, which lead to hardening and an increase in resistance. During determination of the radiation damage resistance, it was found that a decrease in grain size to 50–70 nm leads to a decrease in the degree of radiation damage and the preservation of the resistance of irradiated ceramics to destruction and cracking. Full article

(This article belongs to the Special Issue Advances in Transparent Ceramics and Composites)

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29 pages, 8956 KiB

Open AccessEditor’s ChoiceReview

Novel Photonic Applications of Silicon Carbide

by Haiyan Ou, Xiaodong Shi, Yaoqin Lu, Manuel Kollmuss, Johannes Steiner, Vincent Tabouret, Mikael Syväjärvi, Peter Wellmann and Didier Chaussende

Materials 2023, 16(3), 1014; https://doi.org/10.3390/ma16031014 - 22 Jan 2023

Cited by 37 | Viewed by 8691

Abstract

Silicon carbide (SiC) is emerging rapidly in novel photonic applications thanks to its unique photonic properties facilitated by the advances of nanotechnologies such as nanofabrication and nanofilm transfer. This review paper will start with the introduction of exceptional optical properties of silicon carbide. [...] Read more.

Silicon carbide (SiC) is emerging rapidly in novel photonic applications thanks to its unique photonic properties facilitated by the advances of nanotechnologies such as nanofabrication and nanofilm transfer. This review paper will start with the introduction of exceptional optical properties of silicon carbide. Then, a key structure, i.e., silicon carbide on insulator stack (SiCOI), is discussed which lays solid fundament for tight light confinement and strong light-SiC interaction in high quality factor and low volume optical cavities. As examples, microring resonator, microdisk and photonic crystal cavities are summarized in terms of quality (Q) factor, volume and polytypes. A main challenge for SiC photonic application is complementary metal-oxide-semiconductor (CMOS) compatibility and low-loss material growth. The state-of-the-art SiC with different polytypes and growth methods are reviewed and a roadmap for the loss reduction is predicted for photonic applications. Combining the fact that SiC possesses many different color centers with the SiCOI platform, SiC is also deemed to be a very competitive platform for future quantum photonic integrated circuit applications. Its perspectives and potential impacts are included at the end of this review paper. Full article

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

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14 pages, 2085 KiB

Open AccessEditor’s ChoiceArticle

Numerical Modelling of the Constitutive Behaviour of FRCM Composites through the Use of Truss Elements

by Maria Concetta Oddo, Giovanni Minafó, Marielisa Di Leto and Lidia La Mendola

Materials 2023, 16(3), 1011; https://doi.org/10.3390/ma16031011 - 22 Jan 2023

Cited by 4 | Viewed by 2214

Abstract

The modeling of the mechanical behavior of Fabric Reinforced Cementitious Matrix (FRCM) composites is a difficult task due to the complex mechanisms established at the fibre-matrix and composite-support interface level. Recently, several modeling approaches have been proposed to simulate the mechanical response of [...] Read more.

The modeling of the mechanical behavior of Fabric Reinforced Cementitious Matrix (FRCM) composites is a difficult task due to the complex mechanisms established at the fibre-matrix and composite-support interface level. Recently, several modeling approaches have been proposed to simulate the mechanical response of FRCM strengthening systems, however a simple and reliable procedure is still missing. In this paper, two simplified numerical models are proposed to simulate the tensile and shear bond behavior of FRCM composites. Both models take advantage of truss and non-linear spring elements to simulate the material components and the interface. The proposed approach enables us to deduce the global mechanical response in terms of stress-strain or stress-slip relations. The accuracy of the proposed models is validated against the experimental benchmarks available in the literature. Full article

(This article belongs to the Special Issue Advances in Sustainable Inorganic Matrix Composites for Construction)

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13 pages, 7560 KiB

Open AccessEditor’s ChoiceArticle

Improving the p-Type CuCrO₂ Thin Film’s Electrical and Optical Properties

by Jiaxin Jiang, Yu-Feng You, Dhanapal Vasu, Sheng-Chi Chen, Te-Wei Chiu, Gopi Prashanth and Po Chou Chen

Materials 2023, 16(3), 1000; https://doi.org/10.3390/ma16031000 - 21 Jan 2023

Cited by 4 | Viewed by 3303

Abstract

In this research, we studied the functional properties of CuCrO₂, which is the most promising p-type transparent conductive oxide (TCO). The thin films were fabricated using a spin coating technique. The diffraction patterns were obtained with the help of X-ray diffractions, [...] Read more.

In this research, we studied the functional properties of CuCrO₂, which is the most promising p-type transparent conductive oxide (TCO). The thin films were fabricated using a spin coating technique. The diffraction patterns were obtained with the help of X-ray diffractions, and the optical properties of absorption characteristics were studied using UV-visible absorption. The physical properties of film formation and surface morphology were analyzed using FESEM analysis. The aging properties were also analyzed with the help of various precursors with different aging times. The CuCrO₂ thin films’ functional properties were determined by using chelating agent and precursor solution aging times. The CuCrO₂ thin films have better transmittance, resistance, figure of merit (FOM), and electrical conductivity. Moreover, the resistivity values of the CuCrO₂ thin films are 7.01, 9.90, 12.54, 4.10, 2.42, and 0.35 Ω cm. The current research article covers the preparation of copper chromium delafossite thin films. These thin films can be suitable for hole transport layers in transparent optoelectronic devices. Full article

(This article belongs to the Special Issue Nanostructural Thin Films: Microstructure and Optical Properties)

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13 pages, 2466 KiB

Open AccessEditor’s ChoiceArticle

Decay Kinetics of Gd₃Al₂Ga₃O₁₂:Ce³⁺ Luminescence under Dense Laser Irradiation

by Dmitry Spassky, Andrey Vasil’ev, Nataliya Krutyak, Oleg Buzanov, Vladimir Morozov, Alexei Belik, Nikita Fedorov, Patrick Martin and Andrei Belsky

Materials 2023, 16(3), 971; https://doi.org/10.3390/ma16030971 - 20 Jan 2023

Cited by 4 | Viewed by 1993

Abstract

The decay kinetics of Gd₃Al₂Ga₃O₁₂:Ce³⁺ single crystal luminescence were studied under dense laser excitation. It was shown that the decay times as well as the intensity of Ce³⁺ luminescence depend on the excitation [...] Read more.

The decay kinetics of Gd₃Al₂Ga₃O₁₂:Ce³⁺ single crystal luminescence were studied under dense laser excitation. It was shown that the decay times as well as the intensity of Ce³⁺ luminescence depend on the excitation density. The observed effects were ascribed to the interaction between excitons as well as to the features of energy transfer from the excitons to Ce³⁺. The numerical simulation of the experimental results was performed for justification of the proposed model. Full article

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

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15 pages, 2739 KiB

Open AccessEditor’s ChoiceArticle

Enhancing the Performance of Quantum Dot Light-Emitting Diodes Using Solution-Processable Highly Conductive Spinel Structure CuCo₂O₄ Hole Injection Layer

by Min Ho Park, Min Gye Kim, Jin Hyun Ma, Jun Hyung Jeong, Hyoun Ji Ha, Wonsik Kim, Soohyung Park and Seong Jun Kang

Materials 2023, 16(3), 972; https://doi.org/10.3390/ma16030972 - 20 Jan 2023

Cited by 2 | Viewed by 2532

Abstract

Charge imbalance in quantum-dot light-emitting diodes (QLEDs) causes emission degradation. Therefore, many studies focused on improving hole injection into the QLEDs-emitting layer owing to lower hole conductivity compared to electron conductivity. Herein, CuCo₂O₄ has a relatively higher hole conductivity than [...] Read more.

Charge imbalance in quantum-dot light-emitting diodes (QLEDs) causes emission degradation. Therefore, many studies focused on improving hole injection into the QLEDs-emitting layer owing to lower hole conductivity compared to electron conductivity. Herein, CuCo₂O₄ has a relatively higher hole conductivity than other binary oxides and can induce an improved charge balance. As the annealing temperature decreases, the valence band maximum (VBM) of CuCo₂O₄ shifts away from the Fermi energy level (E_F), resulting in an enhanced hole injection through better energy level alignment with hole transport layer. The maximum luminance and current efficiency of the CuCo₂O₄ hole injection layer (HIL) of the QLED were measured as 93,607 cd/m² and 11.14 cd/A, respectively, resulting in a 656% improvement in luminous performance of QLEDs compared to conventional metal oxide HIL-based QLEDs. These results demonstrate that the electrical properties of CuCo₂O₄ can be improved by adjusting the annealing temperature, suggesting that solution-processed spinel can be applied in various optoelectronic devices. Full article

(This article belongs to the Special Issue Quantum Dots for Optoelectronic Devices)

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13 pages, 2875 KiB

Open AccessEditor’s ChoiceArticle

Modeling and Characterization of Surface Discharges in Insulating Material for Spacers: Electrode Shape, Discharge Mode, and Revision of the Creepage Concept

by Debasish Nath, Qichen Yang, Giancarlo Montanari, Weijun Yin, Han Xiong and Karim Younsi

Materials 2023, 16(3), 989; https://doi.org/10.3390/ma16030989 - 20 Jan 2023

Cited by 11 | Viewed by 2818

Abstract

In the design of MV AC and DC spacers, the predominant factors are surface and interface conditions. Design is generally carried out on specifications and standards which are based on long-term experience and lab testing. However, the diffusion of power electronics with a [...] Read more.

In the design of MV AC and DC spacers, the predominant factors are surface and interface conditions. Design is generally carried out on specifications and standards which are based on long-term experience and lab testing. However, the diffusion of power electronics with a trend to increase electric field, switching frequency, and rise time to achieve higher power density calls for an innovative, global approach to optimized insulation system design. A new methodology, based on field simulation, discharge modeling, and partial discharge inception measurements, called the three-leg approach, can form the basis to optimize insulation design for any type of supply voltage waveform. This paper focuses on the influence of the type of electrode on the inception and phenomenology of surface discharges and, as a consequence, on the interpretation of the results used for application of the three-leg approach. It is demonstrated that a typical electrode system used for insulating material testing can generate both gas and surface discharges at the triple point, when the electrodes have a smooth profile that is used to avoid corona or flashover. Hence, testing partial discharge may not provide a straightforward indication of the surface discharge inception and, thus, be partially misleading for insulation design. Another takeover is that such analysis must benefit from PD testing tools endowed with analytics able to provide automatic identification of the type of defect generating PD, i.e., internal, surface, and corona, since design and remedy actions can be taken, and adequate insulating materials developed, only knowing the type of source generating PD. Hence, testing partial discharge may not provide a straightforward indication of surface discharge inception and, thus, be partially misleading for insulation design. In addition to the importance of the three-leg approach to favor reliable and optimized design of insulation systems, there is a clear need to have a PD testing tool endowed with analytics. It should preferably be able to provide automatic identification of the type of defect generating PD, i.e., internal, surface, and corona. Full article

(This article belongs to the Special Issue Advances in Electric Insulating Materials and Applications)

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14 pages, 7260 KiB

Open AccessEditor’s ChoiceArticle

Tet-Regulated Expression and Optical Clearing for In Vivo Visualization of Genetically Encoded Chimeric dCas9/Fluorescent Protein Probes

by Liliya Maloshenok, Gerel Abushinova, Natalia Kazachkina, Alexei Bogdanov, Jr. and Victoria Zherdeva

Materials 2023, 16(3), 940; https://doi.org/10.3390/ma16030940 - 19 Jan 2023

Cited by 5 | Viewed by 2711

Abstract

The catalytically inactive mutant of Cas9 (dCas9) endonuclease has multiple biomedical applications, with the most useful being the activation/repression of transcription. dCas9 family members are also emerging as potential experimental tools for gene mapping at the level of individual live cells and intact [...] Read more.

The catalytically inactive mutant of Cas9 (dCas9) endonuclease has multiple biomedical applications, with the most useful being the activation/repression of transcription. dCas9 family members are also emerging as potential experimental tools for gene mapping at the level of individual live cells and intact tissue. We performed initial testing on a set of tools for Cas9-mediated visualization of nuclear compartments. We investigated doxycycline (Dox)-inducible (Tet-On) intracellular distribution of constructs encoding dCas9 orthologs from St. thermophilus (St) and N. meningitides (Nm) fused with EGFP and mCherry fluorescent proteins (FP) in human A549 cells. We also studied time-dependent expression of these chimeric fluorescent constructs (dCas9-FP) after Tet-On induction in live cells and compared it with the time course of dCas9-FP expression in experimental dCas9-FP-expressing tumor xenografts using a combination of fluorescence imaging and in vivo contrast-assisted magnetic resonance imaging for assessing the extent of tumor perfusion. In vivo Dox-induction of mCherry-chimera expression occurred in tumor xenografts as early as 24 h post-induction and was visualized by using optical clearing (OC) of the skin. OC via topical application of gadobutrol enabled high-contrast imaging of FP expression in tumor xenografts due to a 1.1–1.2-fold increase in FI in both the red and green channels. Full article

(This article belongs to the Special Issue Advanced Materials for Biophotonics Applications)

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17 pages, 3032 KiB

Open AccessEditor’s ChoiceArticle

Fragmentation Mechanism in a Nitrogen Dielectric Barrier Discharge Plasma on Fluoropolymer Polymer Films

by Faegheh Fotouhiardakani, Morgane Laurent, Jacopo Profili, Sethumadhavan Ravichandran, Gowri Dorairaju and Gaetan Laroche

Materials 2023, 16(3), 942; https://doi.org/10.3390/ma16030942 - 19 Jan 2023

Cited by 7 | Viewed by 3166

Abstract

Due to their chemical inertness and low friction coefficient, fluoropolymers are today widely employed in sectors of activity as diverse and distinct as the textile industry, architectural sector, and medicine. However, their low surface energy results in poor adhesion, for example, when used [...] Read more.

Due to their chemical inertness and low friction coefficient, fluoropolymers are today widely employed in sectors of activity as diverse and distinct as the textile industry, architectural sector, and medicine. However, their low surface energy results in poor adhesion, for example, when used for a component in a composite device with multiple other materials. Among the techniques used to enhance their adhesion, atmospheric pressure discharges provide a fast and low-cost method with a reduced environmental impact. Although this approach has proven to be efficient, the different chemical and physical processes in the discharge remain not fully understood. In this study, fluoropolymer surfaces were modified using an atmospheric pressure dielectric barrier discharge in a nitrogen and organic precursor environment. To prevent any damage to fluoropolymer surfaces, the dissipated power in the discharges was tuned by applying a duty cycle. Evidence shows that plasma treatment allows for the incorporation of oxygen and nitrogen in the surface resulting in the formation of hydrophilic functionalities such as carbonyl groups both in ketone and amide form, amine, and hydroxyl groups after 180 s of treatment. Overall, the data reveal that the discharge duty cycle has more effect on the oxygen and carbon content in the coating than the precursor concentration. In addition, increasing the precursor concentration limits the molecular fragmentation and nitrogen incorporation into the coating. These experiments enable the building of a better fundamental understanding of the formation mechanism of such chemical moieties at the fluoropolymer surface. Full article

(This article belongs to the Special Issue Surface Modifications for Advanced Polymer Composites)

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17 pages, 3942 KiB

Open AccessEditor’s ChoiceArticle

Effect of Ni Substitution on Thermoelectric Properties of Bulk β-Fe_1−xNi_xSi₂ (0 ≤ x ≤ 0.03)

by Sopheap Sam, Soma Odagawa, Hiroshi Nakatsugawa and Yoichi Okamoto

Materials 2023, 16(3), 927; https://doi.org/10.3390/ma16030927 - 18 Jan 2023

Cited by 7 | Viewed by 2829

Abstract

A thermoelectric generator, as a solid-state device, is considered a potential candidate for recovering waste heat directly as electrical energy without any moving parts. However, thermoelectric materials limit the application of thermoelectric devices due to their high costs. Therefore, in this work, we [...] Read more.

A thermoelectric generator, as a solid-state device, is considered a potential candidate for recovering waste heat directly as electrical energy without any moving parts. However, thermoelectric materials limit the application of thermoelectric devices due to their high costs. Therefore, in this work, we attempt to improve the thermoelectric properties of a low-cost material, iron silicide, by optimizing the Ni doping level. The influence of Ni substitution on the structure and electrical and thermoelectric characteristics of bulk β-Fe_xNi_1−xSi₂ (0 ≤ x ≤ 0.03) prepared by the conventional arc-melting method is investigated. The thermoelectric properties are reported over the temperature range of 80–800 K. At high temperatures, the Seebeck coefficients of Ni-substituted materials are higher and more uniform than that of the pristine material as a result of the reduced bipolar effect. The electrical resistivity decreases with increasing x owing to the increases in metallic ε-phase and carrier density. The ε-phase increases with Ni substitution, and solid solution limits of Ni in β-FeSi₂ can be lower than 1%. The highest power factor of 200 μWm⁻¹K⁻² at 600 K is obtained for x = 0.001, resulting in the enhanced ZT value of 0.019 at 600 K. Full article

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

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21 pages, 27547 KiB

Open AccessEditor’s ChoiceReview

Polymer and Composite Materials in Two-Phase Passive Thermal Management Systems: A Review

by Ali Ahmed Alqahtani and Volfango Bertola

Materials 2023, 16(3), 893; https://doi.org/10.3390/ma16030893 - 17 Jan 2023

Cited by 4 | Viewed by 3328

Abstract

The application of polymeric and composite materials in two-phase passive heat transfer devices is reviewed critically, with a focus on advantages and disadvantages of these materials in thermal management systems. Recent technology developments led to an increase of the power density in several [...] Read more.

The application of polymeric and composite materials in two-phase passive heat transfer devices is reviewed critically, with a focus on advantages and disadvantages of these materials in thermal management systems. Recent technology developments led to an increase of the power density in several applications including portable electronics, space and deployable systems, etc., which require high-performance and compact thermal management systems. In this context, passive two-phase systems are the most promising heat transfer devices to dissipate large heat fluxes without external power supply. Usually, heat transfer systems are built with metals due to their excellent thermal properties. However, there is an increasing interest in replacing metallic materials with polymers and composites that can offer cost-effectiveness, light weight and high mechanical flexibility. The present work reviews state-of the-art applications of polymers and composites in two-phase passive thermal management systems, with an analysis of their limitations and technical challenges. Full article

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

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20 pages, 8634 KiB

Open AccessEditor’s ChoiceArticle

Modeling and Vibration Control of Sandwich Composite Plates

by Zhicheng Huang, Huanyou Peng, Xingguo Wang and Fulei Chu

Materials 2023, 16(3), 896; https://doi.org/10.3390/ma16030896 - 17 Jan 2023

Cited by 6 | Viewed by 2479

Abstract

A finite element dynamic model of the sandwich composite plate was developed based on classical laminate theory and Hamilton’s principle. A 4-node, 7-degree-of-freedom three-layer plate cell is constructed to simulate the interaction between the substrate, the viscoelastic damping layer, and the piezoelectric material [...] Read more.

A finite element dynamic model of the sandwich composite plate was developed based on classical laminate theory and Hamilton’s principle. A 4-node, 7-degree-of-freedom three-layer plate cell is constructed to simulate the interaction between the substrate, the viscoelastic damping layer, and the piezoelectric material layer. Among them, the viscoelastic layer is referred to as the complex constant shear modulus model, and the equivalent Rayleigh damping is introduced to represent the damping of the substrate. The established dynamics model has too many degrees of freedom, and the obtained dynamics model has good controllability and observability after adopting the joint reduced-order method of dynamic condensation in physical space and equilibrium in state space. The optimal quadratic (LQR) controller is designed for the active control of the sandwich panel, and the parameters of the controller parameters, the thickness of the viscoelastic layer, and the optimal covering position of the sandwich panel are optimized through simulation analysis. The results show that the finite element model established in this paper is still valid under different boundary conditions and different covering methods, and the model can still accurately and reliably represent the dynamic characteristics of the original system after using the joint step-down method. Under different excitation signals and different boundary conditions, the LQR control can effectively suppress the vibration of the sandwich plate. The optimal cover position of the sandwich plate is near the solid support end and far from the free-degree end. The parameters of controller parameters and viscoelastic layer thickness are optimized from several angles, respectively, and a reasonable optimization scheme can be selected according to the actual requirements. Full article

(This article belongs to the Special Issue Sandwich Composites: Design, Simulation and Applications)

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13 pages, 15329 KiB

Open AccessEditor’s ChoiceArticle

Filtering Efficiency of Sustainable Textile Materials Applied in Personal Protective Face Mask Production during Pandemic

by Attila Géczy, Gergő Havellant, Réka Bátorfi, Agata Skwarek, Karel Dušek, David Bušek and Balázs Illés

Materials 2023, 16(3), 903; https://doi.org/10.3390/ma16030903 - 17 Jan 2023

Cited by 5 | Viewed by 2302

Abstract

The COVID-19 outbreak increased demand for personal protective respirator masks. Textile masks based on cloth materials appeared to be a sustainable, comfortable, and cost-effective alternative available in global communities. In this study, we used laser-based particle counting for mask material qualification to determine [...] Read more.

The COVID-19 outbreak increased demand for personal protective respirator masks. Textile masks based on cloth materials appeared to be a sustainable, comfortable, and cost-effective alternative available in global communities. In this study, we used laser-based particle counting for mask material qualification to determine the concentration filtering efficiency in general, everyday community use. The efficiencies of eleven different commercially available textile materials were measured in single-, double-, and triple-layer configurations according to their grammage, mesh (XY), and inter-yarn gap. It was found that in the single-layer configurations, most materials were well below the acceptable standards, with a wide variation in filtering efficiency, which ranged from 5% to ~50%. However, when testing the fabrics in two or three layers, the efficiency increased significantly, exceeding or approaching the standard for medical masks. Three layers of natural silk was able to produce a level of filtration efficiency of 84.68%. Two-layered natural silk achieved 70.98%, cotton twill achieved 75.6%, and satin-weave viscose achieved 69.77%. Further options can also be considered in cases where lower filtration is acceptable It was statistically shown that applying a second layer was more significant in terms of overall filtering than increasing the layer count to three. However, layer stacking limited the breathability. The paper presents measurement-based qualitative and quantitative recommendations for future textile applications in face mask manufacturing. Full article

(This article belongs to the Special Issue Multifunctional and Protective Textiles)

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20 pages, 2710 KiB

Open AccessEditor’s ChoiceArticle

Modeling Cyclic Crack Propagation in Concrete Using the Scaled Boundary Finite Element Method Coupled with the Cumulative Damage-Plasticity Constitutive Law

by Omar Alrayes, Carsten Könke, Ean Tat Ooi and Khader M. Hamdia

Materials 2023, 16(2), 863; https://doi.org/10.3390/ma16020863 - 16 Jan 2023

Cited by 18 | Viewed by 4625

Abstract

Many concrete structures, such as bridges and wind turbine towers, fail mostly due to the fatigue rapture and bending, where the cracks are initiated and propagate under cyclic loading. Modeling the fracture process zone (FPZ) is essential to understanding the cracking behavior of [...] Read more.

Many concrete structures, such as bridges and wind turbine towers, fail mostly due to the fatigue rapture and bending, where the cracks are initiated and propagate under cyclic loading. Modeling the fracture process zone (FPZ) is essential to understanding the cracking behavior of heterogeneous, quasi-brittle materials such as concrete under monotonic and cyclic actions. The paper aims to present a numerical modeling approach for simulating crack growth using a scaled boundary finite element model (SBFEM). The cohesive traction law is explored to model the stress field under monotonic and cyclic loading conditions. In doing so, a new constitutive law is applied within the cohesive response. The cyclic damage accumulation during loading and unloading is formulated within the thermodynamic framework of the constitutive concrete model. We consider two common problems of three-point bending of a single-edge-notched concrete beam subjected to different loading conditions to validate the developed method. The simulation results show good agreement with experimental test measurements from the literature. The presented analysis can provide a further understanding of crack growth and damage accumulation within the cohesive response, and the SBFEM makes it possible to identify the fracture behavior of cyclic crack propagation in concrete members. Full article

(This article belongs to the Special Issue Computational Mechanics of Structures and Materials)

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11 pages, 4262 KiB

Open AccessEditor’s ChoiceArticle

Construction of Z-Scheme TiO₂/Au/BDD Electrodes for an Enhanced Electrocatalytic Performance

by Kai Zhang, Kehao Zhang, Yuxiang Ma, Hailong Wang, Junyong Shao, Mingliang Li, Gang Shao, Bingbing Fan, Hongxia Lu, Hongliang Xu, Rui Zhang and Huanhuan Shi

Materials 2023, 16(2), 868; https://doi.org/10.3390/ma16020868 - 16 Jan 2023

Cited by 6 | Viewed by 2492

Abstract

TiO₂/Au/BDD composites with a Z-scheme structure was prepared by orderly depositing gold (Au) and titanium dioxide (TiO₂) on the surface of a boron-doped diamond (BDD) film using sputtering and electrophoretic deposition methods. It was found that the introduction of [...] Read more.

TiO₂/Au/BDD composites with a Z-scheme structure was prepared by orderly depositing gold (Au) and titanium dioxide (TiO₂) on the surface of a boron-doped diamond (BDD) film using sputtering and electrophoretic deposition methods. It was found that the introduction of Au between TiO₂ and the BDD, not only could reduce their contact resistance, to increase the carrier transport efficiency, but also could improve the surface Hall mobility of the BDD electrode. Meanwhile, the designed Z-scheme structure provided a fast channel for the electrons and holes combination, to promote the effective separation of the electrons and holes produced in TiO₂ and the BDD under photoirradiation. The electrochemical characterization elucidated that these modifications of the structure obviously enhanced the electrocatalytic performance of the electrode, which was further verified by the simulated wastewater degradation experiments with reactive brilliant red X-3B. In addition, it was also found that the photoirradiation effectively enhanced the pollution degradation efficiency of the modified electrode, especially for the TiO₂/Au/BDD-30 electrode. Full article

(This article belongs to the Section Carbon Materials)

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15 pages, 3493 KiB

Open AccessEditor’s ChoiceReview

Prediction of Novel Ultrahard Phases in the B–C–N System from First Principles: Progress and Problems

by Vladimir L. Solozhenko and Samir F. Matar

Materials 2023, 16(2), 886; https://doi.org/10.3390/ma16020886 - 16 Jan 2023

Cited by 23 | Viewed by 2606

Abstract

The modern synthesis of superhard and, especially, ultrahard phases is a fascinating area of research that could lead to the design of new, industrially important materials. Computational methods built within the well-established quantum mechanics framework of density functional theory (DFT) play an important [...] Read more.

The modern synthesis of superhard and, especially, ultrahard phases is a fascinating area of research that could lead to the design of new, industrially important materials. Computational methods built within the well-established quantum mechanics framework of density functional theory (DFT) play an important role in the search for these advanced materials and the prediction of their properties. The close relationship between the physical properties of carbon and boron nitride has led to particular interest in the B–C–N ternary system, characterized by the small radii of the elements, resulting in short interatomic distances and reduced volumes—the parameters being ‘recipes’ for very high hardness in three-dimensional structures. The purpose of this review is to provide a brief outline of recent developments and problems in predicting novel ultrahard carbon allotropes as well as binary and ternary compounds of the B–C–N system with particular emphasis on the analysis of the models used to evaluate the hardness of the theoretically predicted structures. Full article

(This article belongs to the Special Issue Advances in Density Functional Theory (DFT) Studies of Solids (Second Volume))

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13 pages, 21819 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Fe/Al Ratio and Substrate Hardness on Microstructure and Deposition Behavior of Cold-Sprayed Fe/Al Coatings

by You Wang, Nan Deng, Zhenfeng Tong and Zhangjian Zhou

Materials 2023, 16(2), 878; https://doi.org/10.3390/ma16020878 - 16 Jan 2023

Cited by 4 | Viewed by 2070

Abstract

Fe/Al composite coatings with compositions of Fe-25 wt.% Al, Fe-50 wt.% Al and Fe-75 wt.% Al were deposited on pure Al and P91 steel plates by a cold spray, respectively. The microstructure of the cross-section of the fabricated coatings was characterized by SEM [...] Read more.

Fe/Al composite coatings with compositions of Fe-25 wt.% Al, Fe-50 wt.% Al and Fe-75 wt.% Al were deposited on pure Al and P91 steel plates by a cold spray, respectively. The microstructure of the cross-section of the fabricated coatings was characterized by SEM and EDX. The bonding strength between the coatings and substrates was measured and analyzed. The effects of the Fe/Al ratios and substrate hardness on the deposition behavior were investigated. It was interesting to find fragmented zones in all fabricated coatings, which were composed of large integrated Al particles and small fragmented Al particles. Meanwhile, the fraction of fragmented zones varied with the fraction of the actual Fe/Al ratio. An Fe/Al ratio of 50/50 appeared to be an optimized ratio for the higher bonding strength of coatings. The in situ hammer effect caused by larger and harder Fe particles played an important role in the cold spray process. The substrate with the higher hardness strengthened the in situ hammer effect and further improved the bonding strength. Full article

(This article belongs to the Special Issue Synthesis, Properties and Applications of Intermetallics, Ceramic and Cermet Coatings)

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15 pages, 13247 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Photocatalytic Removal of Antibiotics from Wastewater Using the CeO₂/ZnO Heterojunction

by Nicolae Apostolescu, Ramona Elena Tataru Farmus, Maria Harja, Mihaela Aurelia Vizitiu, Corina Cernatescu, Claudia Cobzaru and Gabriela Antoaneta Apostolescu

Materials 2023, 16(2), 850; https://doi.org/10.3390/ma16020850 - 15 Jan 2023

Cited by 17 | Viewed by 2889

Abstract

CeO₂/ZnO-based photocatalytic materials were synthesized by the sol-gel method in order to establish heterojunctions that increase the degradation efficiency of some types of antibiotics by preventing the recombination of electron–hole pairs. The synthesized materials were analysed by XRD, SEM, EDAX, FTIR, [...] Read more.

CeO₂/ZnO-based photocatalytic materials were synthesized by the sol-gel method in order to establish heterojunctions that increase the degradation efficiency of some types of antibiotics by preventing the recombination of electron–hole pairs. The synthesized materials were analysed by XRD, SEM, EDAX, FTIR, and UV-Vis. After several tests, the optimal concentration of the catalyst was determined to be 0.05 g‧L⁻¹ and 0.025 g‧L⁻¹ for chlortetracycline and 0.05 g‧L⁻¹ for ceftriaxone. CeO₂/ZnO assemblies showed much better degradation efficiency compared to ZnO or CeO₂ tested individually. Sample S3 shows good photocatalytic properties for the elimination of ceftriaxone and tetracycline both from single solutions and from the binary solution. This work provides a different perspective to identify other powerful and inexpensive photocatalysts for wastewater treatment. Full article

(This article belongs to the Special Issue Advanced Materials for Environmental Applications)

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20 pages, 15514 KiB

Open AccessEditor’s ChoiceArticle

Engineering Properties of Green and Ecofriendly Grouting Materials with Different Sand Filling Ratios

by Chuen-Ul Juang and Wen-Ten Kuo

Materials 2023, 16(2), 837; https://doi.org/10.3390/ma16020837 - 15 Jan 2023

Cited by 2 | Viewed by 1845

Abstract

With the active development of offshore wind power worldwide, the development of a green and ecofriendly grouting material (GEGM) has garnered global attention. Such a material must also be developed in Taiwan. Therefore, in this study, a series of environmentally friendly recycled materials [...] Read more.

With the active development of offshore wind power worldwide, the development of a green and ecofriendly grouting material (GEGM) has garnered global attention. Such a material must also be developed in Taiwan. Therefore, in this study, a series of environmentally friendly recycled materials were mixed in different proportions to develop a GEGM which can be implemented in the future construction of offshore wind turbines. To evaluate the mechanical properties of the GEGM, low water-to-binder (W/B) ratios (i.e., 0.21, 0.27, and 0.35) were used; cement was replaced with fixed amounts (20%) of ground granulated blast-furnace slag and fly ash; 2%, 2.5%, and 3% superplasticizers (SPs) were added; and two levels of sand content (60% and 70%) were used. The setting time of the GEGM was used to evaluate its workability; its compressive strength and flexural strength were used to evaluate its mechanical properties; and its sulfate resistance, length changes, and four-terminal resistance were used to evaluate its durability. The relationship between the durability and drying shrinkage of the GEGM was subsequently evaluated, and the ratio of final to initial setting times (F/I value) was calculated to determine the effects of the amount of SP added on workability. The highest F/I value (7.7) was achieved when 2 wt.% modified lignin sulfonate (MLS) was added because of the high viscosity of MLS, which compromised the workability of the concrete. The optimal compressive strength (83.62 MPa) was achieved when a W/B ratio of 0.21 was used, when the sand content was 70%, and when a 2% polycarboxylate superplasticizer (PCE) was added, whereas the optimal flexural strength (20.86 MPa) was achieved when 2.5% PCE was added. According to the nondestructive test results and the R2 value (>0.7) obtained from regression analyses of mechanical properties, the study results are reliable and may serve as a reference for future construction projects. Full article

(This article belongs to the Section Green Materials)

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54 pages, 17421 KiB

Open AccessEditor’s ChoiceReview

A Review of Characterization and Modelling Approaches for Sheet Metal Forming of Lightweight Metallic Materials

by Yong Hou, Dongjoon Myung, Jong Kyu Park, Junying Min, Hyung-Rim Lee, Ali Abd El-Aty and Myoung-Gyu Lee

Materials 2023, 16(2), 836; https://doi.org/10.3390/ma16020836 - 15 Jan 2023

Cited by 48 | Viewed by 8004

Abstract

Lightweight sheet metals are attractive for aerospace and automotive applications due to their exceptional properties, such as low density and high strength. Sheet metal forming (SMF) is a key technology to manufacturing lightweight thin-walled complex-shaped components. With the development of SMF, numerical simulation [...] Read more.

Lightweight sheet metals are attractive for aerospace and automotive applications due to their exceptional properties, such as low density and high strength. Sheet metal forming (SMF) is a key technology to manufacturing lightweight thin-walled complex-shaped components. With the development of SMF, numerical simulation and theoretical modelling are promoted to enhance the performance of new SMF technologies. Thus, it is extraordinarily valuable to present a comprehensive review of historical development in SMF followed by state-of-the-art advanced characterization and modelling approaches for lightweight metallic materials. First, the importance of lightweight materials and their relationship with SMF followed by the historical development of SMF are reviewed. Then, the progress of advanced finite element technologies for simulating metal forming with lightweight alloys is covered. The constitutive modelling of lightweight alloys with an explanation of state-of-the-art advanced characterization to identify the constitutive parameters are presented. Then, the formability of sheet metals with major influencing factors, the techniques for measuring surface strains in SMF and the experimental and modelling approaches for determining the formability limits are clarified. Finally, the review is concluded by affording discussion of the present and future trends which may be used in SMF for lightweight metallic materials. Full article

(This article belongs to the Special Issue Application of Advanced Metal-Forming Technology in Light-Weight Alloys)

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16 pages, 4374 KiB

Open AccessEditor’s ChoiceArticle

Assessment of Convolutional Neural Network Pre-Trained Models for Detection and Orientation of Cracks

by Waqas Qayyum, Rana Ehtisham, Alireza Bahrami, Charles Camp, Junaid Mir and Afaq Ahmad

Materials 2023, 16(2), 826; https://doi.org/10.3390/ma16020826 - 14 Jan 2023

Cited by 33 | Viewed by 5400

Abstract

Failure due to cracks is a major structural safety issue for engineering constructions. Human examination is the most common method for detecting crack failure, although it is subjective and time-consuming. Inspection of civil engineering structures must include crack detection and categorization as a [...] Read more.

Failure due to cracks is a major structural safety issue for engineering constructions. Human examination is the most common method for detecting crack failure, although it is subjective and time-consuming. Inspection of civil engineering structures must include crack detection and categorization as a key component of the process. Images can automatically be classified using convolutional neural networks (CNNs), a subtype of deep learning (DL). For image categorization, a variety of pre-trained CNN architectures are available. This study assesses seven pre-trained neural networks, including GoogLeNet, MobileNet-V2, Inception-V3, ResNet18, ResNet50, ResNet101, and ShuffleNet, for crack detection and categorization. Images are classified as diagonal crack (DC), horizontal crack (HC), uncracked (UC), and vertical crack (VC). Each architecture is trained with 32,000 images equally divided among each class. A total of 100 images from each category are used to test the trained models, and the results are compared. Inception-V3 outperforms all the other models with accuracies of 96%, 94%, 92%, and 96% for DC, HC, UC, and VC classifications, respectively. ResNet101 has the longest training time at 171 min, while ResNet18 has the lowest at 32 min. This research allows the best CNN architecture for automatic detection and orientation of cracks to be selected, based on the accuracy and time taken for the training of the model. Full article

(This article belongs to the Special Issue Machine Learning Techniques in Materials Science and Engineering)

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11 pages, 2761 KiB

Open AccessEditor’s ChoiceArticle

A Highly Versatile X-ray and Electron Beam Diamond Dosimeter for Radiation Therapy and Protection

by Sara Pettinato, Marco Girolami, Antonella Stravato, Valerio Serpente, Daniela Musio, Maria C. Rossi, Daniele M. Trucchi, Riccardo Olivieri and Stefano Salvatori

Materials 2023, 16(2), 824; https://doi.org/10.3390/ma16020824 - 14 Jan 2023

Cited by 20 | Viewed by 3428

Abstract

Radiotherapy is now recognized as a pillar in the fight against cancer. Two different types are currently used in clinical practice: (1) external beam radiotherapy, using high-energy X-rays or electron beams, both in the MeV-range, and (2) intraoperative radiotherapy, using low-energy X-rays (up [...] Read more.

Radiotherapy is now recognized as a pillar in the fight against cancer. Two different types are currently used in clinical practice: (1) external beam radiotherapy, using high-energy X-rays or electron beams, both in the MeV-range, and (2) intraoperative radiotherapy, using low-energy X-rays (up to 50 keV) and MeV-range electron beams. Versatile detectors able to measure the radiation dose independently from the radiation nature and energy are therefore extremely appealing to medical physicists. In this work, a dosimeter based on a high-quality single-crystal synthetic diamond sample was designed, fabricated and characterized under low-energy X-rays, as well as under high-energy pulsed X-rays and electron beams, demonstrating excellent linearity with radiation dose and dose-rate. Detector sensitivity was measured to be 0.299 ± 0.002 µC/Gy under 6 MeV X-ray photons, and 0.298 ± 0.004 µC/Gy under 6 MeV electrons, highlighting that the response of the diamond dosimeter is independent of the radiation nature. Moreover, in the case of low-energy X-rays, an extremely low limit of detection (23 nGy/s) was evaluated, pointing out the suitability of the device to radiation protection dosimetry. Full article

(This article belongs to the Special Issue Recent Advances on Diamond-Based Optical, Electronic, and Optoelectronic Devices)

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16 pages, 3110 KiB

Open AccessEditor’s ChoiceArticle

Polyethylene Glycol-Isophorone Diisocyanate Polyurethane Prepolymers Tailored Using MALDI MS

by Diana-Andreea Blaj, Alexandra-Diana Diaconu, Valeria Harabagiu and Cristian Peptu

Materials 2023, 16(2), 821; https://doi.org/10.3390/ma16020821 - 14 Jan 2023

Cited by 6 | Viewed by 5530

Abstract

The reaction of diols with isocyanates, leading to mono-functional and di-functional prepolymers may be investigated using various characterization methods which show the overall conversion of isocyanate monomers. On the other hand, matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) polymer characterization can be [...] Read more.

The reaction of diols with isocyanates, leading to mono-functional and di-functional prepolymers may be investigated using various characterization methods which show the overall conversion of isocyanate monomers. On the other hand, matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) polymer characterization can be employed to identify the monomer units, the end-group functionalities, molecular weight averages, and to determine the copolymer sequence. Herein, we focus on prepolymer synthesis using isophorone diisocyanate (IPDI), a widely used diisocyanate for prepolymers preparation, especially in waterborne polyurethane materials. Thus, the reaction between polyethylene glycol diol and IPDI was in-depth investigated by mass spectrometry to determine the influence of the reaction parameters on the prepolymer’s structure. The relative content of the different functional oligomer species at given reaction times was determined in the reaction mixture. More specifically, the offline analysis revealed the influence of reaction parameters such as reaction temperature, the concentration of reactants, and the amount of dibutyltin dilaurate catalyst. The established MALDI MS analysis involved measurements of samples, first, directly collected from the reaction mixture and secondly, following derivatization with methanol. The obtained results revealed the effects of reaction parameters on the functionalization reaction with isocyanates, allowing to achieve a better reaction control. Full article

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

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14 pages, 3435 KiB

Open AccessEditor’s ChoiceArticle

Determination of the Dielectric Constant of Niobium Oxide by Using Combined EIS and Ellipsometric Methods

by Krzysztof Fitzner and Michał Stępień

Materials 2023, 16(2), 798; https://doi.org/10.3390/ma16020798 - 13 Jan 2023

Cited by 2 | Viewed by 2699

Abstract

Combining ellipsometric and EIS methods, the dielectric constant ε for the oxide Nb₂O₅ at room temperature was determined. At first, the linear dependence between anodization voltage and oxide thickness was established in the form d = 2.14 (± 0.05) · [...] Read more.

Combining ellipsometric and EIS methods, the dielectric constant ε for the oxide Nb₂O₅ at room temperature was determined. At first, the linear dependence between anodization voltage and oxide thickness was established in the form d = 2.14 (± 0.05) · U + 12.2 (± 1.7) nm in the range of anodizing potentials 0–50 V. Next, assuming the equivalent circuit corresponds to one, the capacitance C of the dense oxide layer was measured. All results taken together gave the value of dielectric constant ε = 93 ± 5. Full article

(This article belongs to the Section Advanced Materials Characterization)

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12 pages, 3422 KiB

Open AccessEditor’s ChoiceArticle

Impact of Bismuth Incorporation into (Ga,Mn)As Dilute Ferromagnetic Semiconductor on Its Magnetic Properties and Magnetoresistance

by Tomasz Andrearczyk, Khrystyna Levchenko, Janusz Sadowski, Katarzyna Gas, Andrei Avdonin, Jerzy Wróbel, Tadeusz Figielski, Maciej Sawicki and Tadeusz Wosinski

Materials 2023, 16(2), 788; https://doi.org/10.3390/ma16020788 - 13 Jan 2023

Cited by 7 | Viewed by 2458

Abstract

The impact of bismuth incorporation into the epitaxial layer of a (Ga,Mn)As dilute ferromagnetic semiconductor on its magnetic and electromagnetic properties is studied in very thin layers of quaternary (Ga,Mn)(Bi,As) compound grown on a GaAs substrate under a compressive misfit strain. An addition [...] Read more.

The impact of bismuth incorporation into the epitaxial layer of a (Ga,Mn)As dilute ferromagnetic semiconductor on its magnetic and electromagnetic properties is studied in very thin layers of quaternary (Ga,Mn)(Bi,As) compound grown on a GaAs substrate under a compressive misfit strain. An addition of a small atomic fraction of 1% Bi atoms, substituting As atoms in the layer, predominantly enhances the spin–orbit coupling strength in its valence band. The presence of bismuth results in a small decrease in the ferromagnetic Curie temperature and a distinct increase in the coercive fields. On the other hand, the Bi incorporation into the layer strongly enhances the magnitude of negative magnetoresistance without affecting the hole concentration in the layer. The negative magnetoresistance is interpreted in terms of the suppression of weak localization in a magnetic field. Application of the weak-localization theory for two-dimensional ferromagnets by Dugaev et al. to the experimental magnetoresistance results indicates that the decrease in spin–orbit scattering length accounts for the enhanced magnetoresistance in (Ga,Mn)(Bi,As). Full article

(This article belongs to the Special Issue Doping and Defect Engineering in Semiconductors)

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35 pages, 8763 KiB

Open AccessEditor’s ChoiceArticle

New Types and Dosages for the Manufacture of Low-Energy Cements from Raw Materials and Industrial Waste under the Principles of the Circular Economy and Low-Carbon Economy

by Sergio Martínez-Martínez, Luis Pérez-Villarejo, Dolores Eliche-Quesada and Pedro J. Sánchez-Soto

Materials 2023, 16(2), 802; https://doi.org/10.3390/ma16020802 - 13 Jan 2023

Cited by 20 | Viewed by 2466

Abstract

The cement manufacturing industry is one of the main greenhouse gas emission producers and also consumes a large quantity of raw materials. It is essential to reduce these emissions in order to comply with the Paris Agreement and the principles of the circular [...] Read more.

The cement manufacturing industry is one of the main greenhouse gas emission producers and also consumes a large quantity of raw materials. It is essential to reduce these emissions in order to comply with the Paris Agreement and the principles of the circular economy. The objective of this research was to develop different types of cement clinker blends using industrial waste and innovative design to produce low-energy cement. Several types of waste have been studied as alternative raw materials. Their main characteristics have been analyzed via X-ray fluorescence (XRF), X-ray diffraction (XRD), Attenuated total reflectance Fourier trans-form infrared spectroscopy (ATR-FTIR), thermal analysis (TG-DTG-DSC) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). The results obtained from the experimental work carried out in this research focused on the study of crude blends for low-energy cement created from industrial waste. The effect of the addition of different industrial waste types, as a substitution for raw materials, in the production of low-energy cement with high dicalcium silicate content has been investigated. Thus, the dosage design has been performed using modified Bogue equations and quality indexes (LSF, AM, and SM). The calculations of both the modified Bogue equations and quality indexes necessitate knowledge of the weight percentages of CaO, SiO₂, Al₂O₃, and Fe₂O₃, determined via XRF. In this theoretical design of the different blends, it has been established that a dicalcium silicate ratio of 60–65 wt % and an LSF of 78–83% as the limit are values common to all of them. The calculation basis for the crude blends has been based on calcined materials. Therefore, the chemical composition was established, following this premise. Thus, it was possible to develop cement clinker blends with compositions of 50 wt % and 100 wt % using industrial wastes. This research has shown that the clinkerization process is one of the main options for the valorization of waste and its consideration for inclusion as a raw material within the circularity of the cement industry’s production process. Thus, waste is used as a raw material for the production of a more useful substance, taking into account the fundamental principles of the circular economy. Full article

(This article belongs to the Special Issue Recycling and Development of New Building Materials or Products)

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13 pages, 4380 KiB

Open AccessEditor’s ChoiceArticle

The Impact of Different Parameters on the Formwork Pressure Exerted by Self-Compacting Concrete

by Yaser Gamil, Andrzej Cwirzen, Jonny Nilimaa and Mats Emborg

Materials 2023, 16(2), 759; https://doi.org/10.3390/ma16020759 - 12 Jan 2023

Cited by 9 | Viewed by 2338

Abstract

Despite the advantageous benefits offered by self-compacting concrete, its uses are still limited due to the high pressure exerted on the formwork. Different parameters, such as those related to concrete mix design, the properties of newly poured concrete, and placement method, have an [...] Read more.

Despite the advantageous benefits offered by self-compacting concrete, its uses are still limited due to the high pressure exerted on the formwork. Different parameters, such as those related to concrete mix design, the properties of newly poured concrete, and placement method, have an impact on form pressure. The question remains unanswered on the degree of the impact for each parameter. Therefore, this study aims to study the level of impact of these parameters, including slump flow, T500 time, fresh concrete density, air content, static yield stress, concrete setting time, and concrete temperature. To mimic the casting scenario, 2 m columns were cast at various casting rates and a laboratory setup was developed. A pressure system that can wirelessly and continuously record pressure was used to monitor the pressure. Each parameter’s impact on the level of pressure was examined separately. Casting rate and slump flow were shown to have a greater influence on pressure. The results also demonstrated that, while higher thixotropy causes form pressure to rapidly decrease, a high casting rate and high slump flow lead to high pressure. This study suggests that more thorough analysis should be conducted of additional factors that may have an impact, such as the placement method, which was not included in this publication. Full article

(This article belongs to the Special Issue Numerical and Experimental Analysis of Advanced Concrete Materials)

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14 pages, 2567 KiB

Open AccessEditor’s ChoiceArticle

Mechanical Properties of a Bone-like Bioceramic–Epoxy-Based Composite Material with Nanocellulose Fibers

by Young-Seong Kim, Jin Woo Baek, Zhengyun Jin, Hee Chang Jeon, Min-Woo Han and Joong Yeon Lim

Materials 2023, 16(2), 739; https://doi.org/10.3390/ma16020739 - 12 Jan 2023

Cited by 3 | Viewed by 2861

Abstract

Several composite materials are being investigated as reinforcement fillers for surgery simulations. This study presents an artificial composite material with properties similar to those of the human bone, which may be used in surgery simulations. Moreover, considering the potential toxicity of debris generated [...] Read more.

Several composite materials are being investigated as reinforcement fillers for surgery simulations. This study presents an artificial composite material with properties similar to those of the human bone, which may be used in surgery simulations. Moreover, considering the potential toxicity of debris generated during sawing, a safe epoxy-based composite material was synthesized using cellulose nanocrystals (CNCs) and bioceramics (i.e., hydroxyapatite, Yttria stabilized zirconia oxide, Zirconia oxide), which were used to mimic the stiffness of human bone. To examine the change in mechanical properties according to the composition, 1, 3, and 5 wt% of CNCs were mixed with 5 wt% of the bioceramics. When CNCs were added at 1 wt%, there was a confirmed change in the non-linear stiffness and ductility. The CNC-added specimen fractured when forming a nano-network around the local CNCs during curing. In contrast, the specimen without CNCs was more densely structured, and combined to form a network of all specimens such that a plastic region could exist. Thus, this study successfully manufactured a material that could mimic longitudinal and transverse characteristics similar to those of real human bone, as well as exhibit mechanical properties such as strength and stiffness. Bioceramics are harmless to the human body, and can be used by controlling the added quantity of CNCs. We expect that this material will be suitable for use in surgery simulations. Full article

(This article belongs to the Section Advanced Composites)

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21 pages, 6540 KiB

Open AccessEditor’s ChoiceReview

Review on Mechanoresponsive Smart Windows: Structures and Driving Modes

by Bo Chen, Qi Feng, Weiwei Liu, Yang Liu, Lili Yang and Dengteng Ge

Materials 2023, 16(2), 779; https://doi.org/10.3390/ma16020779 - 12 Jan 2023

Cited by 8 | Viewed by 3526

Abstract

The growing awareness about the global energy crisis and extreme weather from global warming drives the development of smart windows market. Compared to conventional electrochromic, photochromic, or thermochromic smart windows, mechanoresponsive smart windows present advantages of simple construction, low cost, and excellent stability. [...] Read more.

The growing awareness about the global energy crisis and extreme weather from global warming drives the development of smart windows market. Compared to conventional electrochromic, photochromic, or thermochromic smart windows, mechanoresponsive smart windows present advantages of simple construction, low cost, and excellent stability. In this review, we summarize recent developments in mechanoresponsive smart windows with a focus on the structures and properties. We outline the categories and discuss the advantages and disadvantages. Especially, we also summarize six unconventional driving modes to generate mechanical strain, including pneumatic, optical, thermal, electric, magnetic, and humidity modes. Lastly, we provide practical recommendations in prospects for future development. This review aims to provide a useful reference for the design of novel mechanoresponsive smart windows and accelerate their practical applications. Full article

(This article belongs to the Special Issue Recent Trends in Functional Nanocomposites: Synthesis and Performance)

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