Hasil untuk "Materials of engineering and construction. Mechanics of materials"

Ángel De La Rosa, Gonzalo Ruiz, Vaibhav W. Masih et al.

Mansour Binandeh

Abstract Mainly in the new era, there is a need to accelerate chemical reactions, which is made possible by advanced nanocatalysts, whose magnetic nanocatalysts are highly efficient in controlling chemical reactions such as Sonogashira coupling and alcohol oxidation. Magnetic nanocatalysts are made of magnetite nanoparticles under the chemical co-precipitation method. Their structure was identified by analysis such as EDX (energy-dispersive X-ray) and XRD (X-ray diffraction). The Sonogashira carbon–carbon coupling reaction was performed twice consecutively, and the product efficiency was more than 97%. Oxidation of alcohols to produce aldehyde products is up to 99%. The structure of the magnetic nanocomposite was analyzed after several reuses, and the results showed that it was unchanged, and its performance, structure, and magnetic properties were fully preserved. The reaction conditions are at the lowest possible temperature, harmless solvents, and the highest efficiency percentage, which creates green conditions. The products obtained from the Sonogashira double coupling reaction have two triple bonds. Also, the products with the oxidation of alcohols, which are used as the main precursors in the chemical and medical industries for chemical and pharmaceutical production, are very important.

Xiaoling Zuo, Chuan Liu, Kangan Hao et al.

ABSTRACT The development of advanced information storage materials with spatiotemporal security features is critical to address the growing demand for high‐level encryption and anti‐counterfeiting protection. Herein, two types of 4D‐printed fluorescent hydrogels that exhibit time‐gated hierarchical morphing and color‐varying dual functions, driven solely by temperature, have been successfully developed. Specifically, for the first one, the target blooming state of Hydrogels A is realized under 365 nm UV light through synchronized hierarchical morphing and graded fluorescence color transition (orange→blue). For the second one, under 254 nm UV irradiation, doped Hydrogels B exhibit reversible hierarchical state switching between bloomed and closed configurations, accompanied by dynamic multicolor fluorescence modulation. These promising results originate from spatially gradient crosslinking networks precisely engineered via vat photopolymerization (VP) 3D printing, and specially‐designed luminescent chromophores, collectively enabling fluorescent hydrogels to achieve an all‐in‐one stimulus response integrating “shape morphing—multicolor fluorescence—information encryption” under thermal activation. Thus, a unique “codebook”—a time‐dependent dual‐parameter encryption system can be developed using these 4D‐printed fluorescent hydrogels, by dynamically adjusting bending angles and fluorescence ratios, effectively enabling high‐security spatiotemporal information protection. The integration of time‐gated shape‐shifting and multicolor fluorescence enhances encryption complexity through multi‐layered protection. 4D‐printed fluorescent hydrogels enable this bimodal spatiotemporal strategy, preventing unauthorized access while enabling novel secure storage approaches.

Wangchen Wu, Minmin Ni, Qin Feng et al.

Bacterial cellulose (BC) has been recognized as an ideal supporter owning to its abundant hydroxyl groups on the surface. In this work, Keggin-type phosphotungstic acid (H3PW12O40, PWA) is self-anchored on the three-dimensional network of BC by a simple diffusion method at room-temperature. BC fibers can protect the well-dispersed PWA with high transparency, high mechanical strength, and high stability. When PWA/BC serves as a photochromic material, the coloration time and bleaching time are only 3 min and 30 min respectively. After 6 cycles, the photochromic ability of the PWA/BC composite film almost unchanged. At the same time, we convert the coloration and bleaching degree into quantitative data including a color difference calculation of ΔE2000 and the remaining degree of color (RC%). Within the BC system, PWA exhibits a special linear relationship between RC% and bleaching time (0–30 min). The processes of PWA/BC reduction (W6+→W5+) and oxidation (W5+→W6+) are analysed by photo-electrochromic, XPS and ESR characterizations. The revealed excellent photochromic properties of soft PWA/BC films highlight their potential as the photoresponsive materials.

Luiz A. Riga Junior, Maria V. Riga, Amanda M. P. Santos et al.

Poly(3-decylthiophene) is a polymer with conductive characteristics due to its conjugated polymeric chain. With the search for new applications and improvements of these materials, in sensors, and OPVs, there is a great demand for deeper knowledge about them. This work aims to characterize the P3DT, through analysis of optoelectrical measurements. Using the drop casting technique, thin films were made onto solid substrates. The films were subjected to optical characterization by UV-Vis and optical microscopy. The electrical characterization was obtained by IxV curves and then measuring the photoconductivity through Ixt curves, with a solar simulator. With UV-Vis measurements, it was observed that the absorption of light in the visible spectrum reached a peak of 520 nm in the film, blue-shifted in the solution attributed to the differences in the organization of the polymer chains. The optical microscopy measurements indicate the formation of aggregates with a higher concentration of aggregates observed for the film obtained with a more concentrated solution. Finally, the photoconductivity measurements carried out obtained a positive response to the photo-excitation of the material due to exposure to light, with an increase in current in the film as the photo-exposure cycles were repeated.

Z. Q. Chen, Y. H. Shang, X. D. Liu et al.

Abstract Eutectic alloys have garnered significant attention due to their promising mechanical and physical properties, as well as their technological relevance. However, the discovery of eutectic compositionally complex alloys (ECCAs) (e.g. high entropy eutectic alloys) remains a formidable challenge in the vast and intricate compositional space, primarily due to the absence of readily available phase diagrams. To address this issue, we have developed an explainable machine learning (ML) framework that integrates conditional variational autoencoder (CVAE) and artificial neutral network (ANN) models, enabling direct generation of ECCAs. To overcome the prevalent problem of data imbalance encountered in data-driven ECCA design, we have incorporated thermodynamics-derived data descriptors and employed K-means clustering methods for effective data pre-processing. Leveraging our ML framework, we have successfully discovered dual- or even tri-phased ECCAs, spanning from quaternary to senary alloy systems, which have not been previously reported in the literature. These findings hold great promise and indicate that our ML framework can play a pivotal role in accelerating the discovery of technologically significant ECCAs.

Adrian Gambier

Undoubtedly, wind turbines are currently one of the most significant contributors to clean energy. Therefore, it is crucial to enhance the capability of wind turbines, which in turn leads to an increase in their dimensions. Nevertheless, only advanced control systems can guarantee the optimal and secure operation of these huge machines. On the other hand, the precise control of these modern wind turbines is only achievable through the use of highly specialised actuators. Despite their importance, actuators have historically been overlooked and seen as secondary components in control systems. However, in modern machines, actuators are required to manipulate multiple tonnes or manage thousands of volts and amperes within short times. Consequently, greater emphasis must be placed on their handling and operation. This study aims to review actuators for modern large wind energy converters from a control engineering perspective, using a tutorial approach.

A. F. Baumann, D. Mutter, D. F. Urban et al.

Mechanical stresses and strains in the microstructure of cathode materials evolving during charge/discharge cycles can reduce the long-term stability of intercalation-type alkali-metal-ion batteries. In this context, crystalline compounds exhibiting zero-strain (ZS) behavior are of particular interest. Near-ZS sodiation was experimentally measured in the tetragonal tungsten bronze (TTB) type compound Na$_x$FeF$\mathrm{_3}$. Using a first-principles method based on density functional theory, we investigate the potential of iron-based fluoride compounds with tungsten bronze (TB) structures as ZS cathode materials. Simulations were conducted to study the intercalation of the alkali metal ions Li$\mathrm{^+}$, Na$\mathrm{^+}$, and K$\mathrm{^+}$ into the TTB and two related TB structures of the cubic perovskite (PTB) and hexagonal (HTB) types. We describe compensating local volume effects that can explain the experimentally measured low volume change of Na$_x$FeF$\mathrm{_3}$. We discuss the structural and chemical prerequisites of the host lattice for ZS insertion mechanism for alkali ions in TB structures and present a qualitative descriptor to predict the local volume change, that provides a way for faster screening and discovery of novel ZS battery materials.

Jan Mašek, Josef Květoň, Jan Eliáš

Qinlong Liu, Wei Lu, Jing Zhu et al.

M. V. Berlinov, M. N. Berlinova

An estimated estimate of the long-term operation of a reinforced concrete beam on a ground base is presented, taking into account environmental and dynamic force effects. A method of dynamic calculation of reinforced concrete structures of structures of various types on a ground base operated in an aggressive environment is proposed, internal factors of rheological deformation are also taken into account, taking into account corrosion damage, reflecting their real work under the joint action of the load and the aggressive environment on the basis of the modern phenomenological theory of deformation of the elastic creeping body. It is shown that corrosion damage to reinforced concrete elements can affect the strength of the material, change the calculation schemes, redistribute forces in the cross-sections of the structure and disrupt the joint operation of concrete with reinforcement, as well as lead to other consequences that reduce the design time of operation of structures and other operational characteristics. The possibility of modeling the processes of deformation of reinforced concrete under conditions of long-term operation with a changing mode of action of an external load is shown. An example of the calculation of a reinforced concrete flexible foundation on a soil base is given for the considered service life and the presence of corrosion damage.

Dumitru Alina Iulia, Ion Rodica Mariana, Clicinschi Florentina Marilena et al.

The doped Pb(Zr0.52Ti0.48)O3 system with Nb5+ and Sr2+ were obtained by solid state reactions. The influence of nature of dopants on structural and microstructural properties were analyzed by XRD and SEM techniques and were also investigated the obtained dielectric and piezoelectric properties. The XRD analyzes and the SEM images highlighted the obtaining of homogeneous tetragonal structures, of the perovskite type. The physical (ρa), dielectric constant (ɛr) and piezoelectric (kp) properties of the doped PZT systems were investigated. The Nb5+ doped Pb(Zr0.52Ti0.48)O3 system presented the ɛr = 488 and kp = 0,52. Sr2+ substitution for Nb5+ doped Pb(Zr0.52Ti0.48)O3 reduced the Curie temperature (from 420°C to 360°C), increased the dielectric constant at 1180, and also decreasing the kp (0,39).

Henry T Peng, Musaab Siddiqui

Hemorrhage remains the major cause of death in combat and civilian trauma, although significant advances in hemostatic agents and blood products have enhanced damage control resuscitation and reduced mortality. Currently, few hemostats are available for cessation of non-compressible torso hemorrhage, e.g., intra-abdominal hemorrhage. To address this hard-to-solve problem, self-propelling hemostatic particles composed of coagulation factors e.g., fibrinogen, thrombin, CaCO3 and protonated tranexamic acid (TXA+) that can move against blood flow and promote clot formation have been developed. This paper describes the preparation and characterization of CaCO3-encapsulated fibrinogen/thrombin particles. The particles were prepared by interfacial reaction method using water-oil-water emulsion under different conditions that varied in the concentrations of the coagulation factor and ammonium carbonate solutions, amounts of surfactants, mixing speed, volume ratio between water and oil phases. The resulting CaCO3 encapsulated fibrinogen/thrombin particles were characterized via light microscopy for morphology, gel electrophoresis for presence of fibrinogen and thrombin, rotational thromboelastometry for hemostatic effects and reaction with TXA+ for self-propulsion test. It was found that CaCO3 particles had spherical structure with less than 10 µm in diameter, could encapsulate fibrinogen and thrombin, enhance blood coagulation, and generate bubbles for propulsion by reacting with TXA+. Moreover, when particles were combined with TXA+, a synergistic hemostatic effect was obtained. These hemostatic and self-propelling properties could be optimized via changes to preparation method and composition. Further studies in animal bleeding models are warranted.

R. Z. Xu, X. Du, J. S. Zhou et al.

TaTe$_4$, a metallic charge-density wave (CDW) material discovered decades ago, has attracted renewed attention due to its rich interesting properties such as pressure-induced superconductivity and candidate non-trivial topological phase. Here, using high-resolution angle-resolved photoemission spectroscopy and ab-initio calculation, we systematically investigate the electronic structure of TaTe$_4$. At 26 K, we observe a CDW gap as large as 290 meV, which persists up to 500 K. The CDW-modulated band structure shows a complex reconstruction that closely correlates with the lattice distortion. Inside the CDW gap, there exist highly dispersive energy bands contributing to the remnant Fermi surface and metallic behavior in the CDW state. Interestingly, our ab-initio calculation reveals that the large CDW gap mainly opens in the electronic states with out-of-plane orbital components, while the in-gap metallic states originate from in-plane orbitals, suggesting an orbital texture that couples with the CDW order. Our results shed light on the interplay between electron, lattice, and orbital in quasi-one-dimensional CDW materials.

Alex Hallett, Catalina Avarvarei, John W. Harter

Geometric frustration of magnetic ions can lead to a quantum spin liquid ground state where long range magnetic order is avoided despite strong exchange interactions. The physical realization of quantum spin liquids comprises a major unresolved area of contemporary materials science. One prominent magnetically-frustrated structure is the kagome lattice. The naturally occurring minerals herbertsmithite [ZnCu$_3$(OH)$_6$Cl$_2$] and Zn-substituted barlowite [ZnCu$_3$(OH)$_6$BrF] both feature perfect kagome layers of spin-$1/2$ copper ions and display experimental signatures consistent with a quantum spin liquid state at low temperatures. To investigate other possible candidates within this material family, we perform a systematic first-principles combinatorial exploration of structurally related compounds [$A$Cu$_3$(OH)$_6B_2$ and $A$Cu$_3$(OH)$_6BC$] by substituting non-magnetic divalent cations ($A$) and halide anions ($B$, $C$). After optimizing such structures using density functional theory, we compare various structural and thermodynamic parameters to determine which compounds are most likely to favor a quantum spin liquid state. Convex hull calculations using binary compounds are performed to determine feasibility of synthesis. We also estimate the likelihood of interlayer substitutional disorder and spontaneous distortions of the kagome layers. After considering all of these factors as a whole, we select several promising candidate materials that we believe deserve further attention.

Xiang Wu, Jiaxuan Zhang, Richu Wang et al.

Cu alloys can be plastically deformed to reach ultra-high strength, but often at an expense of their electrical conductivity. Here we report that the introduction of hierarchical precipitations and the resultant microstructural heterogeneities at different scales could overcome the strength-conductivity tradeoff in Cu-Ag-Zr alloy. The intrinsic particle size dependent precipitation behavior, owing to the different cooling rate during powder atomization, has been inherited after hot isostatic pressing (HIP) of powders into bulk sample. The following cold rolling and aging created multi-scale structures with the sub-micron particles at grain boundaries and sub-micron-to-nano scale precipitates in the grain interior. Those introduced heterogeneous precipitate configurations also altered the evolution of deformation structures during cold rolling and aging, with partially recrystallized grains embedded in highly deformed matrix featured by high density of dislocation and substructures, which results in an excellent combination of tensile strength (704 MPa), electrical conductivity (88.7% IACS), and tensile elongation (14.9%). Besides, no significant coarsening in the micro-nano structures is observed after annealing at 450 °C for 1 h. The findings in this work proposed a novel approach for designing high-strength, high-conductivity, and high-thermal stability copper alloys based on hierarchical precipitation-stimulated structures at nano-to-micron scale.

Karina Portillo-Cortez, Selene R. Islas, Amauri Serrano-Lázaro et al.

In this paper, a novel soft deposition methodology was developed for depositing Al-doped ZnO (AZO) thin films as Transparent Conducting Oxide (TCO) layer. The new proposed methodology could help in reducing the process time and cost that could subsequently be useful for industrial scalability purposes. In general, the effect of substrate distance (dTS), Ar gas flow (FAr), and sputtering power (PW) were analyzed on structural, morphological, optical, and electrical properties. Films exhibiting the best electrical values (3.2 × 10−4 Ω*cm, 21.3 cm2 V−1 s−1, and 9.2 × 1020 cm−3) were deposited at FAr of 5 sccm, PW of 45 W, and room temperature. Additionally, AZO thin films deposited inside the high-density zone (HDZ, dTS < 6 cm) of the plasma sputtering exhibited a textured surface with crater-like morphology, and it was found to be more evident in films deposited at reduced FAr (5 sccm) and low PW (45 W) values. The present methodology could be of great interest for the low-cost production of AZO thin films with a textured surface obtained in a one-step DC sputtering process for modern optoelectronic applications such as flexible solar cells and electroluminescent devices.

Sankha Bhattacharya

For non-small cell lung cancer (NSCLC) treatment, a BCS class II drug, Gefitinib, was widely used. Due to poor bioavailability, uncontrollable drug release, Gefitinib witnessed side effects. To circumvent such associated problems, optimized Gefitinib encapsulated polycaprolactone (PCL) nanoparticles with three different molecular weights of PCL (average Mn∼10,000, Mn∼45,000 & Mn∼80,000) were developed using Box–Behnken design while understanding the influence of critical process parameters of the nanoparticles. For morphological characterizations, SEM, TEM, AFM were used. Hemocompatibility, platelet aggregation, and erythrocyte membrane integrity tests were used to test nanoparticles for biocompatibility; excellent biocompatibility was reported during these tests. The in-vitro drug release studies confirmed that Gefitinib-PCL10,000NPs, Gefitinib-PCL45,000NPs, and Gefitinib-PCL80,000 NPs, show significant initial burst effects, and later nanoparticles possessed zero-order kinetics. The genotoxicity of PCL nanoparticles was assessed by cytokinesis-block micronucleus (CBMN) assay, indicating DNA damage in NCI-H460 cell and micronuclei and nuclear buds’ formation. Further, reactive oxygen species studies, MTT cytotoxicity assays at 24 & 48 h, stability, in-vitro cellular uptake of optimized fluorescent Gefitinib PCL80,000NPs, and apoptosis studies were also carried out. As a result, investigating stable Gefitinib-loaded poly-caprolactone (PCL) nanoparticles could open up new research avenues, potentially lowering side effects and improving Gefitinib's profile in the treatment of NSCLC.

Cun Hui, Yonggang Li, Zhongyi Zhou et al.

Adil Hatem Nawar