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

Yury Lysogorskiy, Anton Bochkarev, Ralf Drautz

Abstract Foundational machine learning interatomic potentials that can accurately and efficiently model a vast range of materials are critical for accelerating atomistic discovery. We introduce universal potentials based on the graph atomic cluster expansion (GRACE) framework, trained on several of the largest available materials datasets. Through comprehensive benchmarks, we demonstrate that the GRACE models establish a new Pareto front for accuracy versus efficiency among foundational interatomic potentials. We further showcase their exceptional versatility by adapting them to specialized tasks and simpler architectures via fine-tuning and knowledge distillation, achieving high accuracy while preventing catastrophic forgetting. This work establishes GRACE as a robust and adaptable foundation for the next generation of atomistic modeling, enabling high-fidelity simulations across the periodic table.

Zheng Wei, Wei Cui, Ri-cheng Miao

The viscosity of cement-bentonite (CB) slurry has an important impact on its construction quality and engineering utility. This study focuses on the mechanism of how Na-bentonite (Na-B) influences the viscosity of CB slurry. Four types of Na-B were selected to prepare bentonite slurry and CB slurry, followed by the design of tests to analyze the viscosity differences. Based on these results, microscopic tests, including X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and field emission scanning electron microscopy (FESEM), were conducted to explain the reasons for the different properties of different bentonite slurries and their CB slurries. The analysis demonstrates that the variation in viscosity of bentonite slurry can be elucidated by the principles of viscosity recovery, low shear viscosity failure, and differences in bentonite composition. Meanwhile, the viscosity of CB slurry is influenced by charge adsorption, hydration products, and the interaction between bentonite and cement.

Weijia Dong, Xuan Ji, Chuanbin An et al.

Abstract Organic memristors, integrating chemically designed resistive switching and mechanical flexibility, present promising hardware opportunities for neuromorphic computing, particularly in the development of next‐generation wearable artificial intelligence devices. However, challenges persist in achieving high yield, controllable switching, and multi‐modal information processing. In this study, we introduce an efficient distribution of conversion bridges (EDCB) strategy by dispersing organic semiconductor (poly[2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene], PBTTT) in elastomer (polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene, SEBS). This innovative approach results in memristors with exceptional yield, high stretchability, and reliable switching performance. By fine‐tuning the semiconductor content, we shift the primary charge carriers from ions to electrons, realizing modulable non‐volatile, and volatile duo‐mode memristors. This advancement enables multi‐modal signal processing at distinct operational mechanisms—non‐volatile mode for image recognition in convolutional neural networks (CNNs) and volatile mode for dynamic classification and prediction in reservoir computing (RC). A fully analog RC hardware system is further demonstrated by integrating the distinct volatile and non‐volatile modes of the EDCB‐based memristor into the dynamic neuron network and the linear regression layer of the RC respectively, achieving high accuracy in online arrhythmia detection tasks. Our work paves the way for high‐yield organic memristors with mechanical flexibility, advancing efficient multi‐mode neuromorphic computing within a unified memristor system integrating volatile and non‐volatile functionalities.

Solomon Bekele Endeshaw, Mahendra Goddati, Jaebeom Lee et al.

ZnO/CuO nanocomposites (NCs) were prepared through a biological route using Vernonia amygdalina leaf extract as a stabilizing and reducing agent. ZnO nanoparticles (NPs) and ZnO/CuO NCs were also fabricated via the chemical precipitation method for comparison purposes. Spectroscopic, microscopic, electrochemical and XRD techniques were employed to characterize the prepared samples. In addition, first-principles calculations based on density functional theory (DFT) were utilized to elucidate the electronic characteristics of the individual ZnO and CuO NPs. The X-ray diffraction (XRD) results affirmed the purity and crystalline features of the fabricated NPs and NCs. Morphological analyses demonstrated that the particles of green-mediated ZnO/CuO NCs are smaller and less agglomerated than those of NCs synthesized without the extract. A comparison of photocatalytic and antibacterial performances of ZnO/CuO NCs synthesized with and without plant extract was also conducted. Compared to chemically synthesized NCs, the green-mediated NCs exhibited superior visible light photocatalytic performance for the decomposition of methylene blue (MB) dye. In particular, the degradation of MB over the optimized green-mediated NCs reached 98.80 % within 80 min of photocatalysis, and the degradation rate was achieved as 0.0528 ± 0.00813 min−1. The enhancement might result from the reduced particle size and thereby the enhanced surface area of the green-mediated NCs. In addition, the anti-bactericidal effects of the green-mediated ZnO/CuO NCs against two Gram-negative and two Gram-positive bacteria were significantly higher than those of chemically prepared NC samples. The highest inhibitory zone was observed as 19.0 ± 0.37 mm against E. coli in the presence of the optimized green-mediated NCs. Thus, the biosynthesized ZnO/CuO NCs can be a potential candidate for practical and sustainable antibacterial and photocatalytic applications.

Shuai Ma, Shengli Pang, Xudong He et al.

Solid oxide fuel cells (SOFCs) are of paramount importance for developing green and sustainable energy systems. However, achieving stable nanoscale cathode catalysts under their typically high operating temperatures, normally exceeding 600 °C, remains a significant challenge. By introducing a small amount of RuCl3 into the cathode slurry, an in-situ transformation of the PrBaCo2O5+δ cathode catalyst can be induced from submicrometer-scale irregular particles into nanosheets during SOFC operation. These nanosheets feature a RuO2-modified surface layer, resulting in substantial improvements in both catalytic activity and operational durability. At 750 °C and 0.7 V, SOFCs employing conventional cathode catalysts exhibit a 6.1% degradation in power density over 110 h, while those employing the nanosheet-structured catalysts achieve an 11.9% increase, ultimately stabilizing at a high-power density of 0.75 W/cm2. This work presents a simple and scalable strategy for constructing high-performance nanocatalysts and deepens our theoretical understanding of catalyst nanostructuring for SOFC applications.

Seiji Aota, Masaaki Tanaka

A newly identified class of magnetic materials called altermagnets has attracted much attention due to the practical properties of spin-splitting bands akin to ferromagnets and small compensated magnetization akin to antiferromagnets. These features make them promising candidates for applications in spintronics devices. Among candidate materials, CrSb is promising because of its high ordering temperature (~705 K) and large spin-splitting energy; however, it is predicted that tuning the Néel vector requires additional symmetry breaking or a change in the easy magnetization axis. While applying epitaxial strain can modulate the symmetry, the selection of substrates with closely matched lattice constants for heteroepitaxial growth is limited for altermagnets, which generally have low crystal symmetry. Therefore, exploring the heteroepitaxial growth of altermagnet thin films on well-established, dissimilar crystal systems is valuable. (001)-oriented III-V semiconductors, which share group-V elements with the overgrown CrSb, offer an ideal platform because they are expected to have material compatibility with stable interfaces, as well as tunability of the buffer layer's bandgap and lattice constant by varying the atomic composition of their group-III and group-V atoms. In this study, we have achieved the molecular beam epitaxial growth of a CrSb ($\bar{1}10$) thin film on a GaAs (001) substrate by inserting thin FeSb ($\bar{1}10$) / AlAs (001) buffer layers. The in-plane epitaxial relationship is found to be CrSb [110] $\|$ GaAs [110] and CrSb [001] $\|$ GaAs [$\bar{1}10$], and epitaxial strain is also confirmed. We also characterized the magneto-transport properties of the grown CrSb thin film. Although the obtained conductivity tensors are mainly explained by a two-carrier model, not by an anomalous Hall effect, this model reveals the presence of high-mobility electron and hole carriers.

Junze Zhang, Bingang Xu, Kaili Chen et al.

Abstract Wearable strain sensors have attracted research interest owing to their potential within digital healthcare, offering smarter tracking, efficient diagnostics, and lower costs. Unlike rigid sensors, fiber‐based ones compete with their flexibility, durability, adaptability to body structures as well as eco‐friendliness to environment. Here, the sustainable fiber‐based wearable strain sensors for digital health are reviewed, and material, fabrication, and practical healthcare aspects are explored. Typical strain sensors predicated on various sensing modalities, be it resistive, capacitive, piezoelectric, or triboelectric, are explained and analyzed according to their strengths and weaknesses toward fabrication and applications. The applications in digital healthcare spanning from body area sensing networks, intelligent health management, and medical rehabilitation to multifunctional healthcare systems are also evaluated. Moreover, to create a more complete digital health network, wired and wireless methods of data collection and examples of machine learning are elaborated in detail. Finally, the prevailing challenges and prospective insights into the advancement of novel fibers, enhancement of sensing precision and wearability, and the establishment of seamlessly integrated systems are critically summarized and offered. This endeavor not only encapsulates the present landscape but also lays the foundation for future breakthroughs in fiber‐based wearable strain sensor technology within the domain of digital health.

Mani Valleti, Maxim Ziatdinov, Yongtao Liu et al.

Abstract Electron, optical, and scanning probe microscopy methods are generating ever increasing volume of image data containing information on atomic and mesoscale structures and functionalities. This necessitates the development of the machine learning methods for discovery of physical and chemical phenomena from the data, such as manifestations of symmetry breaking phenomena in electron and scanning tunneling microscopy images, or variability of the nanoparticles. Variational autoencoders (VAEs) are emerging as a powerful paradigm for the unsupervised data analysis, allowing to disentangle the factors of variability and discover optimal parsimonious representation. Here, we summarize recent developments in VAEs, covering the basic principles and intuition behind the VAEs. The invariant VAEs are introduced as an approach to accommodate scale and translation invariances present in imaging data and separate known factors of variations from the ones to be discovered. We further describe the opportunities enabled by the control over VAE architecture, including conditional, semi-supervised, and joint VAEs. Several case studies of VAE applications for toy models and experimental datasets in Scanning Transmission Electron Microscopy are discussed, emphasizing the deep connection between VAE and basic physical principles. Python codes and datasets discussed in this article are available at https://github.com/saimani5/VAE-tutorials and can be used by researchers as an application guide when applying these to their own datasets.

Andi Alijagic, Xuying Wang, Naga Vera Srikanth Vallabani et al.

Abstract Metal additive manufacturing (AM) is gaining traction but raises worker health concerns due to micron‐sized powders, including fine inhalable particles. This study explored particle and surface characteristics, electrochemical properties, metal release in artificial lysosomal fluid (ALF), and potential toxicity of virgin and sieved virgin Fe‐based powders, stainless steel (316L), Fe, and two tooling steels. Virgin particles ranged in size from 1 to 100 µm, while sieved particles were within the respirable size range (<5–10 µm). Surface oxide composition differed from bulk composition. The Fe powder showed low corrosion resistance and high metal release due to a lack of protective surface oxide. Sieved particles of 316L, Fe, and one tooling steel released more metals into ALF than virgin particles, with the opposite was observed for the other tooling steel. Sieved particles had no notable impact on cell viability or micronuclei formation in human bronchial epithelial cells. Inflammatory response in human macrophages was generally low, except for the Fe powder and one tooling steel, which induced increased interleukin‐8 (IL‐8/CXCL‐8) and monocyte chemoattractant protein‐1 (MCP‐1/CCL‐2) secretion. This study underscores distinctions between virgin and sieved Fe‐based powders and suggests relatively low acute toxicity.

Adolfo O. Fumega, Marcel Niedermeier, Jose L. Lado

Super-moiré materials represent a novel playground to engineer states of matter beyond the possibilities of conventional moiré materials. However, from the computational point of view, understanding correlated matter in these systems requires solving models with several millions of atoms, a formidable task for state-of-the-art methods. Conventional wavefunction methods for correlated matter scale with a cubic power with the number of sites, a major challenge for super-moiré materials. Here, we introduce a methodology capable of solving correlated states in super-moiré materials by combining a kernel polynomial method with a quantics tensor cross interpolation matrix product state algorithm. This strategy leverages a mapping of the super-moiré structure to a many-body Hilbert space, that is efficiently sampled with tensor cross interpolation with matrix product states, where individual evaluations are performed with a Chebyshev kernel polynomial algorithm. We demonstrate this approach with interacting super-moiré systems with up to several millions of atoms, showing its ability to capture correlated states in moiré-of-moiré systems and domain walls between different moiré systems. Our manuscript puts forward a widely applicable methodology to study correlated matter in ultra-long length scales, enabling rationalizing correlated super-moiré phenomena.

Tae Hyun Park, Seunggun Yu, Jeongok Park et al.

For changing environmental circumstances, interactive structural color (SC) observation is a promising strategy to store and express external information. SCs based on self-assembled block copolymer (BCP) photonic crystals have been a research focus due to their facile and diverse nanostructures relying on the volume ratio of blocks. Their unique nano-architectonics can reflect incident light due to constructive interference of the two different dielectric constituents. Their excellent ability to change nano-architectonics in response to external stimuli (i.e. humidity, temperature, pH, and mechanical force) allows for a programmable and stimuli-interactive BCP SC display. In this review, recent advances in programmable and stimuli-interactive SC displays with the 1-dimensional self-assembled BCP nano-architectonics are comprehensively discussed. First, this review focuses on the development of programmable BCP SCs that can store various information. Second, stimuli-interactive BCP SCs capable of responding reversibly to external stimuli are also addressed. Particularly, reversible BCP SC changes are suitable for rewritable displays and emerging human-interactive BCP SC displays that detect various human information through changes in electric signals with the simultaneous alteration of the BCP SCs. Based on previously reported literature, the current challenges in this research field are further discussed, and the perspective for future development is presented in terms of material, nano-architectonics, and process.

XU YongTai, ZHANG XueLiang, ZHAO HaiLu

A statistical model of static friction factor of joint surfaces was deduced, which was more in line with the actual situation and takes into account the interaction of asperities and the deformation of the substrate. Based on the contact load model of joint surfaces considering the interaction of asperities and the deformation of the substrate, the statistical model of the static friction factor of joint surfaces considering the interaction of asperities and the deformation of the substrate was deduced according to the definition of the static friction coefficient of joint surfaces. The parameters of joint surfaces measured by the experiment are substituted into the model for simulation, and it is found that the static friction coefficient of joint surfaces considering the asperities interaction and the substrate deformation is larger than that without considering the asperities interaction and the substrate deformation. The influence of the asperities interaction and the substrate deformation decreases with the increase of the dimensionless normal contact load and decreases with the decrease of the dimensionless distance of joint surfaces, and increases with the decrease of the root mean square of the profile height. The simulation results of the model are compared with the experimental data of the static friction factor. The results show that the static friction coefficient of joint surfaces considering the asperities interaction and the substrate deformation is closer to the experimental data, which shows that the model is correct.

Yu Meng, Congcong Wang, Lijie Song et al.

The use of functional nanomaterials to realize tumor therapeutic therapy has received considerable attention. However, a single type of nanomaterial usually can only achieve one specific function, and may cause biosafety problems due to poor metabolism. In this work, we have designed a kind of nanocomposite film based on Bi2Se3 nanosheets and carbon nanotubes, which can achieve efficient photothermal conversion and reactive oxygen species generation under near-infrared laser irradiation. Moreover, the developed films showed good biocompatibility in vivo. The multifunctional films showed remarkable therapeutic effects under 808 nm excitation with 0.3 W/cm2, which avoiding the introduction of nano-reagents into the mice and excessive laser power damage. Our work will provide reference for the use of nanomaterials with heterojunctions in synergistic therapy strategies of photothermal and photodynamic therapy.

Fangyuan Gu, Jie Wang, Zi-Jian Lang et al.

Abstract The polar metallic phase is an unusual metallic phase of matter containing long-range ferroelectric (FE) order in the electronic and atomic structure. Distinct from the typical FE insulating phase, this phase spontaneously breaks the inversion symmetry without global polarization. Unexpectedly, the FE order is found to be dramatically suppressed and destroyed at moderate ~ 10% carrier density. Here, we propose a general mechanism based on carrier-induced quantum fluctuations to explain this puzzling phenomenon. The quantum kinetic effect would drive the formation of polaronic quasi-particles made of the carriers and their surrounding dipoles. The disruption in dipolar directions can therefore weaken or even destroy the FE order. We demonstrate such polaron formation and the associated FE suppression via a concise model using exact diagonalization, perturbation, and quantum Monte Carlo approaches. This quantum mechanism also provides an intuitive picture for many puzzling experimental findings, thereby facilitating new designs of multifunctional FE electronic devices augmented with quantum effects.

ZHAO Jin-guo, YAN Zhi-an

&#x00A0;In order to study the corrosion resistance of CrFeCoNiMo high-entropy alloy, the high-entropy alloy Cr19Fe22Co21Ni25Mo13&#x00A0;was prepared by melting and casting technology. The cast microstructure, phase composition of the high-entropy alloy were studied, and the corrosion resistance between the high-entropy alloy and 304SS was compared. Results showed that the microstructure of the CrFeCoNiMo high-entropy alloy possessed a typical dendrite morphology, in which the dendrite was a typical single-phase FCC solid solution, while the interdendritic was a mixed solid solution containing a FCC phase and a FCC1 phase. Compared with 304SS under the same corrosion condition, CrFeCoNiMo high-entropy alloy had better corrosion resistance and lower corrosion rate in sulfuric acid, hydrochloric acid, nitric acid and sodium chloride solution. Besides, there was no obvious corrosion in the dendrite region of the high entropy alloy, but the corrosion in the interdendrite region was serious, which might be mainly caused by the crystal structure difference between the dendrite region and the interdendrite region.

Igor Hernandes Gomes Marques, Robert Saraiva Matos, Yonny Romaguera-Barcelay et al.

In this paper, we have performed qualitative and quantitative analysis of LuMnO3 thin films surfaces, deposited by spin coating over Pt(111)/TiO2/SiO2/Si substrates, to evaluate their spatial patterns as a function of the film’s sintering temperature. Atomic force microscopy was employed to obtain topographic maps that were extensively analyzed via image processing techniques and mathematical tools. 3D (three-dimensional) topographical images revealed that films sintered at 650°C and 750°C presented the formation of smoother surfaces, while the film sintered at 850°C displayed a rougher surface with a root mean square roughness of ∼2.5 nm. On the other direction, the height distribution of the surface for all films has similar asymmetries and shape, although the film sintered using the highest temperature showed the lower density of rough peaks and a sharper peak shape. The advanced fractal parameters revealed that the film sintered at 850°C is dominated by low spatial frequencies, showing less spatial complexity, higher microtexture homogeneity, and uniform height distribution. These results suggest that the combination of stereometric and fractal parameters can be especially useful for identification of unique topographic spatial patterns in LuMnO3 thin films, helping in their implementation in technological applications, such as photovoltaic solar cells and information magnetic date storage and spintronic devices.

Shouqi Zhang, Shizhao Du, Yuan Ang et al.

To reinforce the inclined web shear crack in the shear span of the prestressed concrete hollow slab beam (PCHSB) on a bridge running for 20 years, a new method of grouting reinforcement was developed. Meanwhile, the grouting material corresponding to this method was developed, so as to improve the shear bearing capacity of prestressed concrete hollow slab. To verify the mechanical performance and reinforcement effect of the strengthened PCHSB, the shear resistance tests were carried out to three pieces of full-scale 20m prestressed concrete hollow slab beam after perfusing reinforcement, whose grouting length was 1.5m, 2.0m, 2.5m respectively. The concrete strain, stiffness, bearing capacity, deflection, crack distribution of beams with different perfusing lengths were tested and compared with those of the beam before reinforcement. The results indicated that the new method of grouting reinforcement with UHPC at the end of the beam could improve the mechanical properties of the beam effectively. The grouting material and the original beam had good cooperative working performance under the test load, which could help to improve the shear bearing capacity effectively, and inhibited the development of oblique cracks. Beyond structural test, temperature of the inner structure was onbseved through a temperature sensor. The evolution of temperature showed the temperature peak UHPC material was reduced significantly. Furthermore, the UHPC material had good filling effect after the reinforced beam was cut apart.

K. K. Iyer, Ram Kumar, S. Rayaprol et al.

We have studied the influence of external pressure up to 1 GPa on the magnetic transitions of the orthorhombic Haldane-spin chain compound Tb2BaNiO5 an exotic multiferroic material. This parent compound is known to undergo Néel ordering at TN1= 63 K and another magnetic transition at TN2= 25K at which ferroelectricity sets in, however, without any change in the magnetic symmetry, but with only a sharp change in the canting angle of Tb 4f and Ni 3d magnetic moments. There is a subtle difference in the antiferromagnetic state above and below TN2, which is supported by the fact that there is a metamagnetic transition below TN2only (for 5 K, at about 60 kOe). We report here that, with the application of external pressure, there is an upward shift of TN1, while TN2 shifts towards lower temperatures. It is interesting that the two magnetic transitions in the same compound behave differently under pressure and the opposite behavior at TN2 is attributed to local distortion leading to ferroelectricity. The results are augmented by temperature dependent x-ray diffraction and positive chemical pressure studies. The chemical pressure caused by the isoelectronic doping at Ba site by Sr reduces both the transition temperatures. Clearly, the external pressure favors antiferromagnetic coupling (that is, leading to TN1 enhancement), whereas the chemical pressure reduces TN1, suggesting important role of the changes in local hybridization induced by doping on magnetism in this material.

Kaixuan Zhang, Youjin Lee, Matthew J. Coak et al.

Robust multi-level spin memory with the ability to write information electrically is a long-sought capability in spintronics, with great promise for applications. Here we achieve nonvolatile and highly energy-efficient magnetization switching in a single-material device formed of van-der-Waals topological ferromagnet Fe3GeTe2, whose magnetic information can be readily controlled by a tiny current. Furthermore, the switching current density and power dissipation are about 400 and 4000 times smaller than those of the existing spin-orbit-torque magnetic random access memory based on conventional magnet/heavy-metal systems. Most importantly, we also demonstrate multi-level states, switched by electrical current, which can dramatically enhance the information capacity density and reduce computing costs. Thus, our observations combine both high energy efficiency and large information capacity density in one device, showcasing the potential applications of the emerging field of van-der-Waals magnets in the field of spin memory and spintronics.

Jordan S. Weaver, Adam L. Pintar, Carlos Beauchamp et al.

High-throughput experiments that use combinatorial samples with rapid measurements can be used to provide process-structure-property information at reduced time, cost, and effort. Developing these tools and methods is essential in additive manufacturing where new process-structure-property information is required on a frequent basis as advances are made in feedstock materials, additive machines, and post-processing. Here we demonstrate the design and use of combinatorial samples produced on a commercial laser powder bed fusion system to study 60 distinct process conditions of nickel superalloy 625: five laser powers and four laser scan speeds in three different conditions. Combinatorial samples were characterized using optical and electron microscopy, x-ray diffraction, and indentation to estimate the porosity, grain size, crystallographic texture, secondary phase precipitation, and hardness. Indentation and porosity results were compared against a regular sample. The smaller-sized regions (3 mm x 4 mm) in the combinatorial sample have a lower hardness compared to a larger regular sample (20 mm x 20 mm) with similar porosity (< 0.03 %). Despite this difference, meaningful trends were identified with the combinatorial sample for grain size, crystallographic texture, and porosity versus laser power and scan speed as well as trends with hardness versus stress-relief condition.