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16 pages, 1881 KiB

Open AccessArticle

Bimodal Absorber Frequencies Shift Induced by the Coupling of Bright and Dark Modes

by Yun Chen, Jiangbo Hu, Shan Yin, Wentao Zhang and Wei Huang

Materials 2024, 17(13), 3379; https://doi.org/10.3390/ma17133379 - 8 Jul 2024

Viewed by 703

In this paper, we demonstrate that the absorption frequencies of the bimodal absorber shift with the coupling strength of the bright and dark modes. The coupling between the bright mode and the dark mode can acquire electromagnetically induced transparency, we obtain the analytical [...] Read more.

In this paper, we demonstrate that the absorption frequencies of the bimodal absorber shift with the coupling strength of the bright and dark modes. The coupling between the bright mode and the dark mode can acquire electromagnetically induced transparency, we obtain the analytical relationship between the absorbing frequencies, the resonant frequencies, losses of the bright mode and dark mode, and the coupling strength between two modes by combining the coupled mode theory with the interference theory. As the coupling strength between the bright mode and the dark mode decreases, the two absorption peaks gradually move closer to each other, inversely, they will move away from each other. The simulation employs three distinct metasurface structures with coupling of the bright and dark modes, thereby verifying the generality of the theoretical findings. Full article

(This article belongs to the Special Issue Terahertz Materials and Technologies in Materials Science)

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14 pages, 3573 KiB

Open AccessArticle

Deformation Behavior of AZ31 Magnesium Alloy with Pre-Twins under Biaxial Tension

by Hanshu Dai, Mengmeng Sun and Yao Cheng

Materials 2024, 17(13), 3377; https://doi.org/10.3390/ma17133377 - 8 Jul 2024

Viewed by 574

Abstract

In the present study, the mechanical response and deformation behavior of a Mg AZ31 plate with different types of pre-twins was systematically investigated under biaxial tension along the normal direction (ND) and transverse direction (TD) with different stress ratios. The results show that [...] Read more.

In the present study, the mechanical response and deformation behavior of a Mg AZ31 plate with different types of pre-twins was systematically investigated under biaxial tension along the normal direction (ND) and transverse direction (TD) with different stress ratios. The results show that significant hardening was observed under biaxial tension. The yield values in the direction of larger stress values were higher than those under uniaxial loading conditions, and the solute atom segregation at twin boundaries generates more obvious strengthening effect. Noting that, for TRH (with cross compression along the rolling direction (RD) and TD and annealing at 180 °C for about 0.5 h) sample, the strength effect of the RD yield stress

σ_{RD} : σ_{ND}

= 2:1 was higher than that of the ND yield stress under stress ratio

σ_{RD} : σ_{ND}

= 1:2. There is a complex competition between twinning and detwinning under biaxal tension along the ND and TD of the pre-twinned samples with the variation in the stress ratio along the TD and RD. The variation in the twin volume fractions for all samples under biaxial firstly decreases and then increases with a higher stress ratio along the ND. As for the TDH sample (precompression along the TD and annealing), the changes of the twin volume fraction were lower than that of the TR sample (cross compression along the TD and RD). However, the amplitude of variation in twin volume fraction of the TRH sample is higher than that of the TR sample. This is because the relative activity of detwinning decreases and that of twinning increases, as the ND stress mainly leads to the growth of pre-twins and the TD stress often promotes detwinning of primary twins. With a higher stress ratio along the ND, the activity of twinning deformation increases and that of detwinning decreases. Full article

(This article belongs to the Section Metals and Alloys)

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12 pages, 3138 KiB

Open AccessArticle

Synthesis of Up-Conversion CaTiO₃: Er³⁺ Films on Titanium by Anodization and Hydrothermal Method for Biomedical Applications

by Nguyen Thi Thanh Tuyen, Ta Quoc Tuan, Le Van Toan, Le Thi Tam and Vuong-Hung Pham

Materials 2024, 17(13), 3376; https://doi.org/10.3390/ma17133376 - 8 Jul 2024

Viewed by 587

Abstract

The present study investigates the effects of Er³⁺ doping content on the microstructure and up-conversion emission properties of CaTiO₃: Er³⁺ phosphors as a potential material in biomedical applications. The CaTiO₃: x%Er³⁺ (x = 0.5, [...] Read more.

The present study investigates the effects of Er³⁺ doping content on the microstructure and up-conversion emission properties of CaTiO₃: Er³⁺ phosphors as a potential material in biomedical applications. The CaTiO₃: x%Er³⁺ (x = 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0%) films were synthesized on Ti substrates by a hydrothermal reaction at 200 °C for 24 h. The SEM image showed the formation of cubic nanorod CaTiO₃: Er³⁺ films with a mean edge size value of (1–5) μm. When excited with 980 nm light, the CaTiO₃: Er³⁺ films emitted a strong green band and a weak red band of Er³⁺ ions located at 543, 661, and 740 nm. The CaTiO₃: Er³⁺ film exhibited excellent surface hydrophilicity with a contact angle of ~zero and good biocompatibility against baby hamster kidney (BHK) cells. CaTiO₃: Er³⁺ films emerge as promising materials for different applications in the biomedical field. Full article

(This article belongs to the Section Thin Films and Interfaces)

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16 pages, 2344 KiB

Open AccessArticle

Effect of Carbon on Void Nucleation in Iron

by Lin Shao

Materials 2024, 17(13), 3375; https://doi.org/10.3390/ma17133375 - 8 Jul 2024

Viewed by 617

Abstract

The study reports the significance of carbon presence in affecting void nucleation in Fe. Without carbon, void nucleation rates decrease gradually at high temperatures but remain significantly high and almost saturated at low temperatures. With carbon present, even at 1 atomic parts per [...] Read more.

The study reports the significance of carbon presence in affecting void nucleation in Fe. Without carbon, void nucleation rates decrease gradually at high temperatures but remain significantly high and almost saturated at low temperatures. With carbon present, even at 1 atomic parts per million, void nucleation rates show a low-temperature cutoff. With higher carbon levels, the nucleation temperature window becomes narrower, the maximum nucleation rate becomes lower, and the temperature of maximum void nucleation shifts to a higher temperature. Fundamentally, this is caused by the change in effective vacancy diffusivity due to the formation of carbon-vacancy complexes. The high sensitivity of void nucleation to carbon comes from the high sensitivity of void nucleation to the vacancy arrival rate in a void. The void nucleation is calculated by first obtaining the effective vacancy diffusivity considering the carbon effect, then calculating the defect concentration and defect flux change considering both carbon effects and pre-existing dislocations, and finally calculating the void nucleation rate based on the recently corrected homogeneous void nucleation theory. The study is important not only in the fundamental understanding of impurity effects in ion/neutron irradiation but also in alloy engineering for judiciously introducing impurities to increase swelling resistance, as well as in the development of simulation and modeling methodologies applicable to other metals. Full article

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12 pages, 26650 KiB

Open AccessArticle

Mechanical and Physicochemical Characteristics of a Novel Premixed Calcium Silicate Sealer

by Naji Kharouf, Filippo Cardinali, Raya Al-Rayesse, Ammar Eid, Ziad Moujaes, Mathilda Nafash, Hamdi Jmal, Frédéric Addiego and Youssef Haikel

Materials 2024, 17(13), 3374; https://doi.org/10.3390/ma17133374 - 8 Jul 2024

Viewed by 747

Abstract

The aim of the present in vitro study was to evaluate specific mechanical and physicochemical properties of three calcium silicate-based sealers, BioRoot™ Flow (BRF), CeraSeal (CRS) and TotalFill^® (TF). Samples were prepared to evaluate different physicochemical and mechanical properties of the tested [...] Read more.

The aim of the present in vitro study was to evaluate specific mechanical and physicochemical properties of three calcium silicate-based sealers, BioRoot™ Flow (BRF), CeraSeal (CRS) and TotalFill^® (TF). Samples were prepared to evaluate different physicochemical and mechanical properties of the tested sealers. These evaluations were accomplished by investigating the pH changes over time, porosity, roughness, flow properties, compressive strength and wettability. The results were statistically evaluated using one-way analysis of variance. All three sealers demonstrated an alkaline pH from 1 h of immersion in water to 168 h. A higher porosity and hydrophily were detected in BRF samples compared to CRS and TF. No significant difference was found between the tested materials in the flow properties. Lower compressive strength values were observed for BRF compared to TF and CRS. Differently shaped structures were detected on the three materials after 7 days of immersion in PBS. The three materials demonstrated a higher solubility than 3% after 24 h of immersion in water (CRS < BRF < TF). The novel premixed calcium silicate sealer (BRF) had comparable physicochemical properties to the existing sealers. The lower compressive strength values could facilitate the removal of these materials during retreatment procedures. Further studies should investigate the biological effects of the novel sealer. Full article

(This article belongs to the Special Issue Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Second Edition))

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15 pages, 4551 KiB

Open AccessArticle

The Impact of Microwave Annealing on MoS₂ Devices Assisted by Neural Network-Based Big Data Analysis

by Xing Su, Siwei Cui, Yifei Zhang, Hui Yang and Dongping Wu

Materials 2024, 17(13), 3373; https://doi.org/10.3390/ma17133373 - 8 Jul 2024

Viewed by 521

Abstract

Microwave annealing, an emerging annealing method known for its efficiency and low thermal budget, has established a foundational research base in the annealing of molybdenum disulfide (MoS₂) devices. Typically, to obtain high-quality MoS₂ devices, mechanical exfoliation is commonly employed. This [...] Read more.

Microwave annealing, an emerging annealing method known for its efficiency and low thermal budget, has established a foundational research base in the annealing of molybdenum disulfide (MoS₂) devices. Typically, to obtain high-quality MoS₂ devices, mechanical exfoliation is commonly employed. This method’s challenge lies in achieving uniform film thickness, which limits the use of extensive data for studying the effects of microwave annealing on the MoS₂ devices. In this experiment, we utilized a neural network approach based on the HSV (hue, saturation, value) color space to assist in distinguishing film thickness for the fabrication of numerous MoS₂ devices with enhanced uniformity and consistency. This method allowed us to precisely assess the impact of microwave annealing on device performance. We discovered a relationship between the device’s electrical performance and the annealing power. By analyzing the statistical data of these electrical parameters, we identified the optimal annealing power for MoS₂ devices as 700 W, providing insights and guidance for the microwave annealing process of two-dimensional materials. Full article

(This article belongs to the Section Energy Materials)

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13 pages, 2716 KiB

Open AccessArticle

Naphthenic Acid Corrosion Mitigation: The Role of Niobium in Low-Carbon Steel

by Nurliyana Mohamad Arifin, Kesahvanveraragu Saravanan and Ervina Efzan Mhd Noor

Materials 2024, 17(13), 3372; https://doi.org/10.3390/ma17133372 - 8 Jul 2024

Viewed by 541

Abstract

Naphthenic acid corrosion is a well-recognized factor contributing to corrosion in the construction of offshore industry pipelines. To mitigate the corrosive effects, minor quantities of alloying elements are introduced into the steel. This research specifically explores the corrosion effects arising from immersing low-carbon [...] Read more.

Naphthenic acid corrosion is a well-recognized factor contributing to corrosion in the construction of offshore industry pipelines. To mitigate the corrosive effects, minor quantities of alloying elements are introduced into the steel. This research specifically explores the corrosion effects arising from immersing low-carbon steel, specifically A333 Grade 6, in a naphthenic acid solution. Various weight percentages of niobium were incorporated, and the resulting properties were observed. It was noted that the addition of 2% niobium in low-carbon steel exhibited the least mass loss and a lower corrosion rate after a 12 h immersion in naphthenic acid. Microstructural analysis using scanning electron microscopy (SEM) revealed small white particles, indicating the presence of oil sediment residue, along with corrosion pits. Following the addition of 2% niobium, the occurrence of corrosion pits markedly decreased, and only minor voids were observed. Additionally, the chemical composition analysis using energy-dispersive X-Ray analysis (EDX) showed that the black spot exhibited the highest percentage of carbon, resembling high corrosion attack. Meanwhile, the whitish regions with low carbon content indicated the lowest corrosion attack. The results demonstrated that the addition of 2% niobium yielded optimal properties for justifying corrosion effects. Therefore, low-carbon steel with a 2% niobium addition can be regarded as a superior corrosion-resistant material for offshore platform pipeline applications. Full article

(This article belongs to the Section Corrosion)

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15 pages, 10448 KiB

Open AccessArticle

Identifying Optimal Processing Variables and Investigating Mechanisms of Grain Alignment in Hot-Deformed NdFeB Magnets through Design of Experiments

by Jongbin Ahn, Jung-Goo Lee and Wooyoung Lee

Materials 2024, 17(13), 3371; https://doi.org/10.3390/ma17133371 - 8 Jul 2024

Viewed by 534

Abstract

This study introduces a novel approach for investigating hot-deformed NdFeB magnets by combining the minimal stress deformation process (MSDP) with the design of experiment (DoE) methodology. This study focused on enhancing the crystallographic alignment, particularly the c-axis alignment of the Nd₂Fe [...] Read more.

This study introduces a novel approach for investigating hot-deformed NdFeB magnets by combining the minimal stress deformation process (MSDP) with the design of experiment (DoE) methodology. This study focused on enhancing the crystallographic alignment, particularly the c-axis alignment of the Nd₂Fe₁₄B grains, to optimize the magnetic properties. By utilizing the Box-Behnken design matrix and response surface regression, critical processes and variables were identified, determining that a hot-pressing temperature of 700 °C is crucial for achieving optimal grain alignment. Changing the strain rate to 0.019 mm/s under a stress of 110 MPa led to significant enhancements in the alignment, yielding magnets with a remanence of approximately 13.4 kG and a coercivity of 21 kOe. These findings highlight the effectiveness of combining the MSDP and DoE for predicting and achieving improved magnetic properties. Despite the challenges associated with understanding the complexity of crystal alignment mechanisms, this integrated approach successfully improved magnetic characteristics. The methodology represents a significant advancement in the fabrication of high-performance hot-deformed NdFeB magnets, marking a notable contribution to the field. Full article

(This article belongs to the Special Issue Fabrication, Characterization, and Development of Hot-Deformed Magnets)

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14 pages, 18667 KiB

Open AccessArticle

Mechanical Properties of Silicon Carbide Composites Reinforced with Reduced Graphene Oxide

by Kamil Broniszewski, Jarosław Woźniak, Tomasz Cygan, Dorota Moszczyńska and Andrzej Olszyna

Materials 2024, 17(13), 3370; https://doi.org/10.3390/ma17133370 - 8 Jul 2024

Viewed by 505

Abstract

This article presents research on the influence of reduced graphene oxide on the mechanical properties of silicon carbide matrix composites sintered with the use of the Spark Plasma Sintering method. The produced sinters were subjected to a three-point bending test. An increase in [...] Read more.

This article presents research on the influence of reduced graphene oxide on the mechanical properties of silicon carbide matrix composites sintered with the use of the Spark Plasma Sintering method. The produced sinters were subjected to a three-point bending test. An increase in flexural strength was observed, which reaches a maximum value of 503.8 MPa for SiC–2 wt.% rGO composite in comparison to 323 MPa for the reference SiC sample. The hardness of composites decreases with the increase in rGO content down to 1475 HV10, which is correlated with density results. Measured fracture toughness values are burdened with a high standard deviation due to the presence of rGO agglomerates. The K_IC reaches values in the range of 3.22–3.82 MPa*m^1/2. Three main mechanisms responsible for the increase in the fracture toughness of composites were identified: bridging, deflecting, and branching of cracks. Obtained results show that reduced graphene oxide can be used as a reinforcing phase to the SiC matrix, with an especially visible impact on flexural strength. Full article

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

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8 pages, 1329 KiB

Open AccessCommunication

Unified Solid Solution Product of [Nb][C] in Nb-Microalloyed Steels with Various Carbon Contents

by Yongming Yan, Yanjun Xue, Ke Liu, Wenchao Yu, Jie Shi and Maoqiu Wang

Materials 2024, 17(13), 3369; https://doi.org/10.3390/ma17133369 - 8 Jul 2024

Viewed by 484

Abstract

In this work, the solid solution product of [Nb][C] in the Nb-microalloyed steels with various carbon contents in the range of 0.20~1.80 wt.% was investigated by means of the extraction phase analysis method. The results showed that the Nb content in austenite tended [...] Read more.

In this work, the solid solution product of [Nb][C] in the Nb-microalloyed steels with various carbon contents in the range of 0.20~1.80 wt.% was investigated by means of the extraction phase analysis method. The results showed that the Nb content in austenite tended to first decrease and then increase with the increase of carbon content in the steels. A unified solid solution product of [Nb][C] in austenite at different temperatures was obtained according to the results of the experimental steels. The Nb content in austenite of the experimental steels with high carbon contents was lower than that calculated by Ohtani’s equation. The existence of NbC precipitates in the case and the core of the specimens carburized at 930 °C and 980 °C were verified by transmission electron microscopy (TEM) observations. The pinning effect of NbC precipitates on austenite grain growth was calculated according to the size and amount of NbC precipitates in the carburized case and the core of the carburized specimens. The calculated results of prior austenite grain sizes were in good agreement with the experimental results, which indicated that the unified solid solution product of [Nb][C] in Nb-microalloyed steels with various carbon contents was applicable for the low-pressure carburizing process. Full article

(This article belongs to the Section Metals and Alloys)

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14 pages, 8459 KiB

Open AccessArticle

Performance and Morphology of Waterborne Polyurethane Asphalt in the Vicinity of Phase Inversion

by Chengwei Wu, Haocheng Yang, Xinpeng Cui, Yachun Chen, Zhonghua Xi, Jun Cai, Junsheng Zhang and Hongfeng Xie

Materials 2024, 17(13), 3368; https://doi.org/10.3390/ma17133368 - 8 Jul 2024

Viewed by 621

Abstract

Waterborne polyurethane asphalt emulsion (WPUA) is an environmentally friendly bituminous material, whose performance is highly dependent on the phase structure of the continuous phase. In this paper, WPUAs in the vicinity of phase inversion were prepared using waterborne polyurethane (WPU) and asphalt emulsion. [...] Read more.

Waterborne polyurethane asphalt emulsion (WPUA) is an environmentally friendly bituminous material, whose performance is highly dependent on the phase structure of the continuous phase. In this paper, WPUAs in the vicinity of phase inversion were prepared using waterborne polyurethane (WPU) and asphalt emulsion. The chemical structures, thermal stability, dynamic mechanical properties, phase-separated morphology and mechanical performance of WPUAs were studied. Fourier-transform infrared (FTIR) spectra revealed that there are no –NCO bonds in either the pure WPU or WPUAs. Moreover, the preparation of WPUA is a physical process. The addition of WPU weakens the thermal stability of asphalt emulsion. WPU improves the storage modulus of asphalt emulsion at lower and higher temperatures. The glass transition temperatures of the WPUA films are higher than that of the pure WPU film. When the WPU concentration increases from 30 wt% to 40 wt%, phase inversion occurs; that is, the continuous phase shifts from asphalt to WPU. The WPUA films have lower tensile strength and toughness than the pure WPU film. However, the elongations at break of the WPUA films are higher than that of the pure WPU film. Both the tensile strength and toughness of the WPUA films increase with the WPU concentration. Due to the occurrence of phase inversion, the elongation at break, tensile strength and toughness of the WPUA film containing 30 wt% WPU are increased by 29%, 250% and 369%, respectively, compared to the film with 40 wt% WPU. Full article

(This article belongs to the Special Issue Multiphase Systems with Polymeric Matrices: Polymer Blends and Composites II)

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15 pages, 5814 KiB

Open AccessArticle

Verification of the Laser Powder Bed Fusion Performance of 2024 Aluminum Alloys Modified Using Nano-LaB₆

by Zeyu Yao and Ziwen Xie

Materials 2024, 17(13), 3367; https://doi.org/10.3390/ma17133367 - 8 Jul 2024

Viewed by 721

Abstract

The application of 2024 aluminum alloy (comprising aluminum, copper, and magnesium) in the aerospace industry is extensive, particularly in the manufacture of seats. However, this alloy faces challenges during laser powder bed fusion (PBF-LB/M) processing, which often leads to solidification and cracking issues. [...] Read more.

The application of 2024 aluminum alloy (comprising aluminum, copper, and magnesium) in the aerospace industry is extensive, particularly in the manufacture of seats. However, this alloy faces challenges during laser powder bed fusion (PBF-LB/M) processing, which often leads to solidification and cracking issues. To address these challenges, LaB₆ nanoparticles have been investigated as potential grain refiners. This study systematically examined the impact of adding different amounts of LaB₆ nanoparticles (ranging from 0.0 to 1.0 wt.%) on the microstructure, phase composition, grain size, and mechanical properties of the composite material. The results demonstrate that the addition of 0.5 wt.% LaB₆ significantly reduces the average grain size from 10.3 μm to 9 μm, leading to a significant grain refinement effect. Furthermore, the tensile strength and fracture strain of the LaB₆-modified A2024 alloy reach 251 ± 2 MPa and 1.58 ± 0.12%, respectively. These findings indicate that the addition of appropriate amounts of LaB₆ nanoparticles can effectively refine the grains of 2024 aluminum alloy, thereby enhancing its mechanical properties. This discovery provides important support for the broader application of 2024 aluminum alloy in the aerospace industry and other high-performance fields. Full article

(This article belongs to the Section Metals and Alloys)

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11 pages, 13214 KiB

Open AccessArticle

Three-Dimensional Printing of Yttrium Oxide Transparent Ceramics via Direct Ink Writing

by Qiming Chen, Huibing Li, Weijie Han, Jian Yang, Wentao Xu and Youfu Zhou

Materials 2024, 17(13), 3366; https://doi.org/10.3390/ma17133366 - 8 Jul 2024

Viewed by 666

Abstract

The utilization of 3D printing technology for the fabrication of intricate transparent ceramics overcomes the limitations associated with conventional molding processes, thereby presenting a highly promising solution. In this study, we employed direct ink writing (DIW) to prepare yttrium oxide transparent ceramics using [...] Read more.

The utilization of 3D printing technology for the fabrication of intricate transparent ceramics overcomes the limitations associated with conventional molding processes, thereby presenting a highly promising solution. In this study, we employed direct ink writing (DIW) to prepare yttrium oxide transparent ceramics using a ceramic slurry with excellent moldability, solid content of 45 vol%, and shear-thinning behavior. A successfully printed transparent yttrium oxide ring measuring 30 mm in diameter, 10 mm in inner diameter, and 0.9 mm in thickness was obtained from the aforementioned slurry. After de-binding and sintering procedures, the printed ceramic exhibited in-line transmittance of 71% at 850 nm. This work not only produced complex yttria transparent ceramics with intricate shapes, but also achieved in-line transmittance that was comparable to that of the CIP method (79%), which can meet certain optical applications. Full article

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

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14 pages, 4920 KiB

Open AccessArticle

Investigating the Anticancer Potential of Zinc and Magnesium Alloys: From Base Materials to Nanocoated Titanium Implants

by Andrij Milenin, Łukasz Niedźwiedzki, Karolina Truchan, Grzegorz Guzik, Sławomir Kąc, Grzegorz Tylko and Anna Maria Osyczka

Materials 2024, 17(13), 3365; https://doi.org/10.3390/ma17133365 - 8 Jul 2024

Viewed by 799

Abstract

In this work, we show the in vitro anticancer potential of surgical wires, obtained from zinc (ZnMg0.004) or magnesium (MgCa0.7) alloys by spatial technology comprising casting, extrusion, and final drawing processes. We also present the selective anticancer effects of applied soluble multilayer nanocoatings [...] Read more.

In this work, we show the in vitro anticancer potential of surgical wires, obtained from zinc (ZnMg0.004) or magnesium (MgCa0.7) alloys by spatial technology comprising casting, extrusion, and final drawing processes. We also present the selective anticancer effects of applied soluble multilayer nanocoatings of zinc and magnesium onto titanium surfaces using the pulse laser deposition method. In the latter, the titanium samples were produced via 3D printing using the selective laser melting method and coated with various combinations of zinc and magnesium layers. For cytotoxicity studies, human dental pulp-derived stem cells (hDPSCs) and human osteosarcoma SaOS-2 cell line were used as representatives of healthy and cancer cells. Cells were examined against the 0.3–3.0 cm²/mL material extract ratios obtained from experimental and steel surgical wires, the latter being the current clinical industry standard. The MgCa0.7 alloy wires were approx. 1.5 times more toxic to cancer cells at all examined extract ratios vs. the extracts from steel surgical wires that exhibited comparable toxicity towards healthy and cancer cells. The ZnMg0.004 alloy wires displayed increased toxicity towards cancer cells with decreasing extract ratios. This was also reflected in the increased anticancer effectiveness, calculated based on the viability ratio of healthy cells to cancer cells, from 1.1 to 4.0 times. Healthy cell viability remained at 80–100%, whereas cancer cell survival fluctuated at 20–75%, depending on the extract ratio. Furthermore, the culture of normal or cancer cells on the surface of Zn/Mg-coated titanium allowed us to select combinations of specific coating layers that yielded a comparable anticancer effectiveness to that observed with the experimental wires that ranged between 2 and 3. Overall, this work not only demonstrates the substantial anticancer properties of the studied wires but also indicates that similar anticancer effects can be replicated with appropriate nanocoatings on titanium samples. We believe that this work lays the groundwork for the future potential development of the category of new implants endowed with anticancer properties. Full article

(This article belongs to the Special Issue Biocompatible and Bioactive Materials for Medical Applications)

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12 pages, 1697 KiB

Open AccessArticle

Electronic Properties and Mechanical Stability of Multi-Ion-Co-Intercalated Bilayered V₂O₅

by Chunhui Ma and Bo Zhou

Materials 2024, 17(13), 3364; https://doi.org/10.3390/ma17133364 - 8 Jul 2024

Viewed by 596

Abstract

Incorporating metal cations into V₂O₅ has been proven to be an effective method for solving the poor long-term cycling performance of vanadium-based oxides as electrodes for mono- or multivalent aqueous rechargeable batteries. This is due to the existence of a [...] Read more.

Incorporating metal cations into V₂O₅ has been proven to be an effective method for solving the poor long-term cycling performance of vanadium-based oxides as electrodes for mono- or multivalent aqueous rechargeable batteries. This is due to the existence of a bilayer structure with a large interlayer space in the V₂O₅ electrode and to the fact that the intercalated ions act as pillars to support the layered structure and facilitate the diffusion of charged carriers. However, a fundamental understanding of the mechanical stability of multi-ion-co-intercalated bilayered V₂O₅ is still lacking. In this paper, a variety of pillared vanadium pentoxides with two types of co-intercalated ions were studied. The root-mean-square deviation of the V-O bonds and the elastic constants calculated by density functional theory were used as references to evaluate the stability of the intercalated compounds. The d-band center and electronic band structures are also discussed. Our theoretical results show that the structural characteristics and stability of the system are quite strongly influenced by the intercalating strategy. Full article

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14 pages, 10383 KiB

Open AccessArticle

Development of Carbon Black Coating on TPU Elastic Powder for Selective Laser Sintering

by Yu-Deh Chao, Shu-Cheng Liu, Dong-Quan Yeh, Ajeet Kumar, Jung-Ting Tsai, Mayur Jiyalal Prajapati and Jeng-Ywan Jeng

Materials 2024, 17(13), 3363; https://doi.org/10.3390/ma17133363 - 8 Jul 2024

Viewed by 772

Abstract

Increased usage of selective laser sintering (SLS) for the production of end-use functional components has generated a requirement of developing new materials and process improvements to improve the applicability of this technique. This article discusses a novel process wherein carbon black was applied [...] Read more.

Increased usage of selective laser sintering (SLS) for the production of end-use functional components has generated a requirement of developing new materials and process improvements to improve the applicability of this technique. This article discusses a novel process wherein carbon black was applied to the surface of TPU powder to reduce the laser reflectivity during the SLS process. The printing was carried out with a preheating temperature of 75 °C, laser energy density of 0.028 J/mm², incorporating a 0.4 wt % addition of carbon black to the TPU powder, and controlling the powder layer thickness at 125 μm. The mixed powder, after printing, shows a reflectivity of 13.81%, accompanied by the highest average density of 1.09 g/cm³, hardness of 78 A, tensile strength of 7.9 MPa, and elongation at break was 364.9%. Compared to commercial TPU powder, which lacks the carbon black coating, the reflectance decreased by 1.78%, mechanical properties improved by 33.9%, and there was a notable reduction in the porosity of the sintered product. Full article

(This article belongs to the Special Issue Development of Advanced Materials Using Additive Manufacturing Technologies)

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17 pages, 5110 KiB

Open AccessReview

Research and Progress on Organic Semiconductor Power Devices

by Fangyi Li, Jiayi Zhou, Jun Zhang and Jiang Zhao

Materials 2024, 17(13), 3362; https://doi.org/10.3390/ma17133362 - 8 Jul 2024

Viewed by 3236

Abstract

Organic semiconductor power devices have been attracting increasing attention due to their advantages such as flexibility, low fabrication cost, and sustainability. They have found wide applications in fields such as flexible electronic devices and biomedical devices. However, in the field of power applications, [...] Read more.

Organic semiconductor power devices have been attracting increasing attention due to their advantages such as flexibility, low fabrication cost, and sustainability. They have found wide applications in fields such as flexible electronic devices and biomedical devices. However, in the field of power applications, the lack of reliable organic semiconductor power devices is mainly attributed to the limited thermal stability and electrical stability of organic materials. This article provides a detailed review of the development status of organic semiconductor power devices from three aspects: device structure, organic materials, and fabrication methods. It clarifies that the future development goal is to enhance the voltage resistance and thermal stability of organic transistors through higher-performance structure design, higher-mobility materials, and higher-quality fabrication methods. The continuous innovation and development of the structures, materials, and fabrication of these devices will generate more novel devices, offering more possibilities for the application of organic semiconductor power devices. This information is of great reference value and guidance significance for engineers in related fields. Full article

(This article belongs to the Special Issue Optoelectronic Semiconductor Materials and Devices)

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14 pages, 12957 KiB

Open AccessArticle

Dynamic Response of Ti-6Al-2Zr-1Mo-1V Alloy Manufactured by Laser Powder-Bed Fusion

by Hanzhao Qin, Alafate Maierdan, Nan Li, Changshun Wang and Chenglin Li

Materials 2024, 17(13), 3361; https://doi.org/10.3390/ma17133361 - 8 Jul 2024

Viewed by 663

Abstract

Titanium parts fabricated by additive manufacturing, i.e., laser or electron beam-powder bed fusion (L- or EB-PBF), usually exhibit columnar grain structures along the build direction, resulting in both microstructural and mechanical anisotropy. Post-heat treatments are usually used to reduce or eliminate such anisotropy. [...] Read more.

Titanium parts fabricated by additive manufacturing, i.e., laser or electron beam-powder bed fusion (L- or EB-PBF), usually exhibit columnar grain structures along the build direction, resulting in both microstructural and mechanical anisotropy. Post-heat treatments are usually used to reduce or eliminate such anisotropy. In this work, Ti-6Al-2Zr-1Mo-1V (TA15) alloy samples were fabricated by L-PBF to investigate the effect of post-heat treatment and load direction on the dynamic response of the samples. Post-heat treatments included single-step annealing at 800 °C (HT) and a hot isotropic press (HIP). The as-built and heat-treated samples were dynamically compressed using a split Hopkinson pressure bar at a strain rate of 3000 s⁻¹ along the horizontal and vertical directions paralleled to the load direction. The microstructural observation revealed that the as-built TA15 sample exhibited columnar grains with fine martensite inside. The HT sample exhibited a fine lamellar structure, whereas the HIP sample exhibited a coarse lamellar structure. The dynamic compression results showed that post-heat treatment at 800 °C led to reduced flow stress but enhanced uniform plastic strain and damage absorption work. However, the HIP samples exhibited both higher stress, uniform plastic strain, and damage absorption work owing to the microstructure coarsening. Additionally, the load direction had a subtle influence on the flow stress, indicating the negligible anisotropy of flow stress in the samples. However, there was more significant anisotropy of the uniform plastic strain and damage absorption. The samples had a higher load-bearing capacity when dynamically compressed perpendicular to the build direction. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume III)

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10 pages, 2451 KiB

Open AccessArticle

Investigation of Grain Boundary Effects in Sm_0.2Ce_0.8O_2−x Thin Film Memristors

by Weikai Shi, Luyao Wang and Nan Yang

Materials 2024, 17(13), 3360; https://doi.org/10.3390/ma17133360 - 8 Jul 2024

Viewed by 744

Abstract

Cerium-based materials (CeO_2−x) are of significant interest in the development of vacancy-modulated resistive switching (RS) memory devices. However, the influence of grain boundaries on the performance of memristors is very limited. To fill this gap, this study explores the influence of [...] Read more.

Cerium-based materials (CeO_2−x) are of significant interest in the development of vacancy-modulated resistive switching (RS) memory devices. However, the influence of grain boundaries on the performance of memristors is very limited. To fill this gap, this study explores the influence of grain boundaries in cerium-based thin film resistive random-access memory (RRAM) devices. Sm_0.2Ce_0.8O_2−x (SDC20) thin films were deposited on (100)-oriented Nb-doped SrTiO₃ (NSTO) and (110)-oriented NSTO substrates using pulsed laser deposition (PLD). Devices constructed with a Pt/SDC20/NSTO structure exhibited reversible and stable bipolar resistive switching (RS) behavior. The differences in conduction mechanisms between single-crystal and polycrystalline devices were confirmed, with single-crystal devices displaying a larger resistance window and higher stability. Combining the results of XPS and I–V curve fitting, it was confirmed that defects near the grain boundaries in the SDC-based memristors capture electrons, thereby affecting the overall performance of the RRAM devices. Full article

(This article belongs to the Special Issue Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application)

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11 pages, 8775 KiB

Open AccessArticle

Modification of Microstructure and Mechanical Properties of Extruded AZ91-0.4Ce Magnesium Alloy through Addition of Ca

by Fengtao Ni, Jian Peng, Xiangquan Liu, Pan Gao, Zhongkui Nie, Jie Hu and Dong Zhao

Materials 2024, 17(13), 3359; https://doi.org/10.3390/ma17133359 - 8 Jul 2024

Viewed by 634

Abstract

The effect of the addition of alkali earth element Ca on the microstructure and mechanical properties of extruded AZ91-0.4Ce-xCa (x = 0, 0.4, 0.8, 1.2 wt.%) alloys was studied by using scanning electron microscopy, transmission electron microscopy, and tensile tests. The results showed [...] Read more.

The effect of the addition of alkali earth element Ca on the microstructure and mechanical properties of extruded AZ91-0.4Ce-xCa (x = 0, 0.4, 0.8, 1.2 wt.%) alloys was studied by using scanning electron microscopy, transmission electron microscopy, and tensile tests. The results showed that the addition of Ca could significantly refine the second phase and grain size of the extruded AZ91-0.4Ce alloy. The refinement effect was most obvious when 0.8 wt.% of Ca was added, and the recrystallized grain size was 4.75 μm after extrusion. The addition of Ca resulted in the formation of a spherical Al₂Ca phase, which effectively suppressed the precipitation of the β-Mg₁₇Al₁₂ phase, promoted dynamic recrystallization and grain refinement, impeded dislocation motion, and exerted a positive influence on the mechanical properties of the alloy. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of the AZ91-0.4Ce-0.8Ca alloy were 238.7 MPa, 338.3 MPa, and 10.8%, respectively. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys)

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27 pages, 10839 KiB

Open AccessArticle

Feasibility and Application of Local Closed-Loop Materials to Produce Compressed and Stabilized Earth Blocks

by Catalina Reyna-Ruiz, José Manuel Gómez-Soberón and María Neftalí Rojas-Valencia

Materials 2024, 17(13), 3358; https://doi.org/10.3390/ma17133358 - 7 Jul 2024

Viewed by 1228

Abstract

The validation of a feasible application for the production of sustainable bricks with local materials in humid and hot climates, which would allow the current housing needs of a constantly growing population with scarce economic resources to be met while also reducing energy [...] Read more.

The validation of a feasible application for the production of sustainable bricks with local materials in humid and hot climates, which would allow the current housing needs of a constantly growing population with scarce economic resources to be met while also reducing energy inputs for climate control, is a current challenge without a definitive solution. Therefore, this research studied the incorporation of local aggregates and two second-generation materials to produce lime-stabilized Compressed Earth Blocks (CSEBs) using a semi-automatic machine for their manufacture. An initial matrix was designed as a baseline, and three more were developed with variations to incorporate second-generation materials individually and as mixtures. The stabilizer was added in concentrations of 5, 10, and 15%, resulting in a total of 12 batches of CSEBs. Eleven of the studied batches exceed the normative limits for simple compressive strength and initial water absorption coefficient. The best result of simple compressive strength was obtained in two batches of the same matrix that used construction demolition waste (CDW), reaching 4.3 MPa (43% above the minimum limit established by the most restrictive regulations and 115% above the least restrictive). It was possible to produce sustainable bricks in situ with average ambient temperatures of 32 °C and relative humidity of 91%. Full article

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

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16 pages, 4524 KiB

Open AccessArticle

The Effect of Rapeseed Oil Biopolyols and Cellulose Biofillers on Selected Properties of Viscoelastic Polyurethane Foams

by Tomasz Prociak, Dariusz Bogdal, Maria Kuranska, Olga Dlugosz and Mark Kubik

Materials 2024, 17(13), 3357; https://doi.org/10.3390/ma17133357 - 7 Jul 2024

Viewed by 632

Abstract

This paper presents the results of research on polyurethane viscoelastic foams (PUVFs) modified with biomaterials. This investigation looked at the effect of the biomaterials on the foaming processes, as well as the acoustical and selected physical-mechanical properties of the foams. Various types of [...] Read more.

This paper presents the results of research on polyurethane viscoelastic foams (PUVFs) modified with biomaterials. This investigation looked at the effect of the biomaterials on the foaming processes, as well as the acoustical and selected physical-mechanical properties of the foams. Various types of rapeseed oil biopolyols and microcellulose were used to modify the materials. The analysis of properties covered a reference biopolyol-free sample and materials containing 10 wt.%, 20 wt.%, and 30 wt.% of different types of biopolyols in the mixture of polyol components. The biopolyols differed in terms of functionality and hydroxyl value (OH_v). Next, a selected formulation was modified with various microcellulose biofillers in the amount of 0.5–2 wt.%. The PUVFs, with apparent densities of more than 210 kg/m³ and open-cell structures (more than 85% of open cells), showed a slow recovery to their original shape after deformation when the pressure force was removed. They were also characterized by a tensile strength in the range of 156–264 kPa, elongation at break of 310–510%, hardness of 8.1–23.1 kPa, and a high comfort factor of 3.1–7.1. The introduction of biopolyols into the polyurethane system resulted in changes in sound intensity levels of up to 31.45%, while the addition of fillers resulted in changes in sound intensity levels of up to 13.81%. Full article

(This article belongs to the Section Polymeric Materials)

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8 pages, 2729 KiB

Open AccessCommunication

A Zn-Ca-Based Metallic Glass Composite Material for Rapid Degradation of Azo Dyes

by Gaojiong Wang, Xin Wang, Wei Yang, Lichen Zhao and Yumin Qi

Materials 2024, 17(13), 3356; https://doi.org/10.3390/ma17133356 - 7 Jul 2024

Viewed by 703

Abstract

The catalytic capabilities of metals in degrading azo dyes have garnered extensive interest; however, selecting highly efficient metals remains a significant challenge. We have developed a Zn-Ca-based metallic glass composite which shows outstanding degradation efficiency for Direct Blue 6. This alloy comprises a [...] Read more.

The catalytic capabilities of metals in degrading azo dyes have garnered extensive interest; however, selecting highly efficient metals remains a significant challenge. We have developed a Zn-Ca-based metallic glass composite which shows outstanding degradation efficiency for Direct Blue 6. This alloy comprises a Zn₂Ca crystalline phase and an amorphous matrix, allowing for the degradation of azo dyes within minutes in a wide temperature range of 0–60 °C. Kinetic calculations reveal an exceptionally low activation energy of 8.99 kJ/mol. The rapid degradation is attributed to the active element Ca and the unique amorphous structure of the matrix, which not only facilitates abundant redox conditions but also minimizes the hydrolysis of the active element. The newly developed metallic glass composite exhibits a notably higher azo dye degradation rate compared to those of general metallic glasses, offering a new avenue for the rapid degradation of azo dyes. This paper holds significant importance for the development of novel azo dye wastewater treatment agents. Full article

(This article belongs to the Special Issue Physical Metallurgy of Metals and Alloys II)

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12 pages, 2490 KiB

Open AccessArticle

Impact of Scattering Foil Composition on Electron Energy Distribution in a Clinical Linear Accelerator Modified for FLASH Radiotherapy: A Monte Carlo Study

by James C. L. Chow and Harry E. Ruda

Materials 2024, 17(13), 3355; https://doi.org/10.3390/ma17133355 - 7 Jul 2024

Viewed by 737

Abstract

This study investigates how scattering foil materials and sampling holder placement affect electron energy distribution in electron beams from a modified medical linear accelerator for FLASH radiotherapy. We analyze electron energy spectra at various positions—ionization chamber, mirror, and jaw—to evaluate the impact of [...] Read more.

This study investigates how scattering foil materials and sampling holder placement affect electron energy distribution in electron beams from a modified medical linear accelerator for FLASH radiotherapy. We analyze electron energy spectra at various positions—ionization chamber, mirror, and jaw—to evaluate the impact of Cu, Pb-Cu, Pb, and Ta foils. Our findings show that close proximity to the source intensifies the dependence of electron energy distribution on foil material, enabling precise beam control through material selection. Monte Carlo simulations are effective for designing foils to achieve desired energy distributions. Moving the sampling holder farther from the source reduces foil material influence, promoting more uniform energy spreads, particularly in the 0.5–10 MeV range for 12 MeV electron beams. These insights emphasize the critical role of tailored material selection and sampling holder positioning in optimizing electron energy distribution and fluence intensity for FLASH radiotherapy research, benefiting both experimental design and clinical applications. Full article

(This article belongs to the Special Issue Artificial Intelligence in Materials Science and Engineering)

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17 pages, 8487 KiB

Open AccessArticle

Strength Optimisation of Hybrid Bolted/Bonded Composite Joints Based on Finite Element Analysis

by Raphael Blier, Leila Monajati, Masoud Mehrabian and Rachid Boukhili

Materials 2024, 17(13), 3354; https://doi.org/10.3390/ma17133354 - 6 Jul 2024

Viewed by 798

Abstract

A finite element analysis (FEA) was conducted to examine the behaviour of single-lap quasi-isotropic (QI) and cross-ply (CP) hybrid bolted/bonded (HBB) configurations subjected to tensile shear loading. Several critical design factors influencing the composite joint strength, failure conditions, and load-sharing mechanisms that would [...] Read more.

A finite element analysis (FEA) was conducted to examine the behaviour of single-lap quasi-isotropic (QI) and cross-ply (CP) hybrid bolted/bonded (HBB) configurations subjected to tensile shear loading. Several critical design factors influencing the composite joint strength, failure conditions, and load-sharing mechanisms that would optimise the joining performance were assessed. The study of the stress concentration around the holes and along the adhesive layer highlights the fact that the HBB joints benefit from significantly lower stresses compared to only bolted joints, especially for CP configurations. The simulation results confirmed the redundancy of the middle bolt in a three-bolt HBB joint. The stiffness and plastic behaviour of the adhesive were found to be important factors that define the transition of the behaviour of the joint from a bolted type, where load sharing is predominant, to a bonded joint. The load-sharing potential, known as an indicator of the joint’s performance, is improved by reducing the overlap length, using a low-stiffness, high-plasticity adhesive, and using thicker laminates in the QI layup configuration. Enhancing both the ratio of the edge distance to the hole diameter and washer size proves advantageous in reducing stresses within the adhesive layer, thereby improving the joint strength. Full article

(This article belongs to the Special Issue Manufacturing and Mechanics of Materials, Volume II)

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15 pages, 6521 KiB

Open AccessArticle

Preparation and Immobilization Mechanism of Red Mud/Steel Slag-Based Geopolymers for Solidifying/Stabilizing Pb-Contaminated Soil

by Xinyang Wang and Yongjie Xue

Materials 2024, 17(13), 3353; https://doi.org/10.3390/ma17133353 - 6 Jul 2024

Viewed by 832

Abstract

Pb-contaminated soil poses serious hazards to humans and ecosystems and is in urgent need of remediation. However, the extensive use of traditional curing materials such as ordinary Portland cement (OPC) has negatively impacted global ecology and the climate, so there is a need [...] Read more.

Pb-contaminated soil poses serious hazards to humans and ecosystems and is in urgent need of remediation. However, the extensive use of traditional curing materials such as ordinary Portland cement (OPC) has negatively impacted global ecology and the climate, so there is a need to explore low-carbon and efficient green cementitious materials for the immobilization of Pb-contaminated soils. A red mud/steel slag-based (RM/SS) geopolymer was designed and the potential use of solidifying/stabilizing heavy metal Pb pollution was studied. The Box–Behnken design (BBD) model was used to design the response surface, and the optimal preparation conditions of RM/SS geopolymer (RSGP) were predicted by software of Design-Expert 8.0.6.1. The microstructure and phase composition of RSGP were studied by X-ray diffractometer, Fourier transform infrared spectrometer, scanning electron microscopy and X-ray photoelectron spectroscopy, and the immobilization mechanism of RSGP to Pb was revealed. The results showed that when the liquid–solid ratio is 0.76, the mass fraction of RM is 79.82% and the modulus of alkali activator is 1.21, the maximum unconfined compressive strength (UCS) of the solidified soil sample is 3.42 MPa and the immobilization efficiency of Pb is 71.95%. The main hydration products of RSGP are calcium aluminum silicate hydrate, calcium silicate hydrate and nekoite, which can fill the cracks in the soil, form dense structures and enhance the UCS of the solidified soil. Pb is mainly removed by lattice immobilization, that is, Pb participates in geopolymerization by replacing Na and Ca to form Si-O-Pb or Al-O-Pb. The remaining part of Pb is physically wrapped in geopolymer and forms Pb(OH)₂ precipitate in a high-alkali environment. Full article

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

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20 pages, 5923 KiB

Open AccessEditor’s ChoiceArticle

Engineered Mesoporous Silica-Based Nanoparticles: Characterization of Surface Properties

by Antonio Grisolia, Marzia De Santo, Manuela Curcio, Palmira Alessia Cavallaro, Catia Morelli, Antonella Leggio and Luigi Pasqua

Materials 2024, 17(13), 3352; https://doi.org/10.3390/ma17133352 - 6 Jul 2024

Viewed by 897

Abstract

Mesoporous silica-based nanomaterials have emerged as multifunctional platforms with applications spanning catalysis, medicine, and nanotechnology. Since their synthesis in the early 1990s, these materials have attracted considerable interest due to their unique properties, including high surface area, tunable pore size, and customizable surface [...] Read more.

Mesoporous silica-based nanomaterials have emerged as multifunctional platforms with applications spanning catalysis, medicine, and nanotechnology. Since their synthesis in the early 1990s, these materials have attracted considerable interest due to their unique properties, including high surface area, tunable pore size, and customizable surface chemistry. This article explores the surface properties of a series of MSU-type mesoporous silica nanoparticles, elucidating the impact of different functionalization strategies on surface characteristics. Through an extensive characterization utilizing various techniques, such as FTIR, Z-potential, and nitrogen adsorption porosimetry, insights into the surface modifications of mesoporous silica nanoparticles are provided, contributing to a deeper understanding of their nanostructure and related interactions, and paving the way to possible unexpected actionability and potential applications. Full article

(This article belongs to the Special Issue Physical Synthesis, Properties and Applications of Nanoparticles)

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15 pages, 4986 KiB

Open AccessArticle

Relevant Aspects in the Mechanical and Aging Degradation of NiTi Alloy with R-Phase in Endodontic Files

by Patricia Sánchez, Benedetta Vidi, Cristina Rico, Jesús Mena-Alvarez, Javier Gil and Juan Manuel Aragoneses

Materials 2024, 17(13), 3351; https://doi.org/10.3390/ma17133351 - 6 Jul 2024

Viewed by 540

Abstract

One of the most important challenges in endodontics is to have files that have excellent flexibility, toughness, and high fatigue life. Superelastic NiTi alloys have been a breakthrough and the new R-phase NiTi alloys promise to further optimize the good properties of NiTi [...] Read more.

One of the most important challenges in endodontics is to have files that have excellent flexibility, toughness, and high fatigue life. Superelastic NiTi alloys have been a breakthrough and the new R-phase NiTi alloys promise to further optimize the good properties of NiTi alloys. In this work, two austenitic phase endodontic files with superelastic properties (Protaper and F6) and two austenitic phase files with the R-phase (M-wire and Reciproc) have been studied. The transformation temperatures were studied by calorimetry. Molds reproducing root canals at different angles (30, 45, and 70°) were obtained with cooling and loads simulating those used in the clinic. Mechanical cycles of different files were realized to fracture. Transformation temperatures were determined at different number of cycles. The different files were heat treated at 300 and 500 °C as the aging process, and the transformation temperatures were also determined. Scanning and transmission electron microscopy was used to observe the fractography and precipitates of the files. The results show that files with the R-phase have higher fracture cycles than files with only the austenitic phase. The fracture cycles depend on the angle of insertion in the root canal, with the angle of 70° being the one with the lowest fracture cycles in all cases. The R-Phase transformation increases the energy absorbed by the NiTi to produce the austenitic to R-phase and to produce the martensitic transformation causing the increase in the fracture cycles. Mechanical cycling leads to significant increases in the transformation temperatures M_s and A_f as well as R_s and R_f. No changes in the transformation temperatures were observed for aging at 300 °C, but the appearance of Ni₄Ti₃ precipitates was observed in the aging treatments to the Nickel-rich files that correspond to those with the R transition. These results should be considered by endodontists to optimize the type of files for clinical therapy. Full article

(This article belongs to the Special Issue Orthodontic Materials: Properties and Effectiveness of Use)

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11 pages, 3241 KiB

Open AccessArticle

Detecting Internal Defects in FRP-Reinforced Concrete Structures through the Integration of Infrared Thermography and Deep Learning

by Pengfei Pan, Rongpeng Zhang, Yi Zhang and Hongbo Li

Materials 2024, 17(13), 3350; https://doi.org/10.3390/ma17133350 - 6 Jul 2024

Viewed by 655

Abstract

This study represents a significant advancement in structural health monitoring by integrating infrared thermography (IRT) with cutting-edge deep learning techniques, specifically through the use of the Mask R-CNN neural network. This approach targets the precise detection and segmentation of hidden defects within the [...] Read more.

This study represents a significant advancement in structural health monitoring by integrating infrared thermography (IRT) with cutting-edge deep learning techniques, specifically through the use of the Mask R-CNN neural network. This approach targets the precise detection and segmentation of hidden defects within the interfacial layers of Fiber-Reinforced Polymer (FRP)-reinforced concrete structures. Employing a dual RGB and thermal camera setup, we captured and meticulously aligned image data, which were then annotated for semantic segmentation to train the deep learning model. The fusion of the RGB and thermal imaging significantly enhanced the model’s capabilities, achieving an average accuracy of 96.28% across a 5-fold cross-validation. The model demonstrated robust performance, consistently identifying true negatives with an average specificity of 96.78% and maintaining high precision at 96.42% in accurately delineating damaged areas. It also showed a high recall rate of 96.91%, effectively recognizing almost all actual cases of damage, which is crucial for the maintenance of structural integrity. The balanced precision and recall culminated in an average F1-score of 96.78%, highlighting the model’s effectiveness in comprehensive damage assessment. Overall, this synergistic approach of combining IRT and deep learning provides a powerful tool for the automated inspection and preservation of critical infrastructure components. Full article

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

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21 pages, 5652 KiB

Open AccessArticle

Dynamic Adhesive Behavior and Biofilm Formation of Staphylococcus aureus on Polylactic Acid Surfaces in Diabetic Environments

by María Fernández-Grajera, Miguel A. Pacha-Olivenza, María Coronada Fernández-Calderón, María Luisa González-Martín and Amparo M. Gallardo-Moreno

Materials 2024, 17(13), 3349; https://doi.org/10.3390/ma17133349 - 6 Jul 2024

Viewed by 703

Abstract

Interest in biodegradable implants has focused attention on the resorbable polymer polylactic acid. However, the risk of these materials promoting infection, especially in patients with existing pathologies, needs to be monitored. The enrichment of a bacterial adhesion medium with compounds that are associated [...] Read more.

Interest in biodegradable implants has focused attention on the resorbable polymer polylactic acid. However, the risk of these materials promoting infection, especially in patients with existing pathologies, needs to be monitored. The enrichment of a bacterial adhesion medium with compounds that are associated with human pathologies can help in understanding how these components affect the development of infectious processes. Specifically, this work evaluates the influence of glucose and ketone bodies (in a diabetic context) on the adhesion dynamics of S. aureus to the biomaterial polylactic acid, employing different approaches and discussing the results based on the physical properties of the bacterial surface and its metabolic activity. The combination of ketoacidosis and hyperglycemia (GK2) appears to be the worst scenario: this system promotes a state of continuous bacterial colonization over time, suppressing the stationary phase of adhesion and strengthening the attachment of bacteria to the surface. In addition, these supplements cause a significant increase in the metabolic activity of the bacteria. Compared to non-enriched media, biofilm formation doubles under ketoacidosis conditions, while in the planktonic state, it is glucose that triggers metabolic activity, which is practically suppressed when only ketone components are present. Both information must be complementary to understand what can happen in a real system, where planktonic bacteria are the ones that initially colonize a surface, and, subsequently, these attached bacteria end up forming a biofilm. This information highlights the need for good monitoring of diabetic patients, especially if they use an implanted device made of PLA. Full article

(This article belongs to the Special Issue Synthesis, Degradation and Biocompatibility of Bioresorbable Materials)

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