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

Mudassir Mehmood, Wen Nie, Yunlong Liu et al.

Expansive soils pose a significant challenge to civil infrastructure due to their high potential for expansion and contraction. These soils exhibit poor mechanical properties, leading to severe structural damage and high maintenance costs. To address these challenges, conventional stabilization like cement or lime, are widely used; however, their production substantially increases global carbon dioxide emissions and energy requirements. Therefore, there is an urgent need to develop sustainable alternatives that enhance soil performance while minimizing environmental impact by utilizing industrial by-products. In response to this need, this study proposes a sustainable composite reinforcement scheme that combines enzyme-induced carbonate precipitation (EICP), sisal fiber (SFs) reinforcement, and iron ore tailings (IOts) to treat expansive soil by deploying laboratory testing and response surface modeling (RSM). Utilizing the experimental and validated optimal mix (0.75 mol/L EICP + 0.53 % SFs + 11.7 % IOts) reduced swelling pressure ∼98 % while increasing the unconfined compressive strength ∼262 %, cohesion ∼78 %, the angle of internal friction ∼172 %, Unsoaked California Bearing Ratio (CBRunsoak) from 2.4 % to ∼26 % and CBRsoak 1.7 % to ∼20 % after 28 days curing. In addition, SEM and EDS analyses confirmed synergistic microstructural interactions, resulting in a highly reinforced soil composite. Moreover, the RSM model showed good agreement with the experimental results, with errors controlled within ±5 %, validating the robustness of the model. By reusing mining waste and utilizing renewable fibers, this approach demonstrates a low-carbon, cost-effective, and scalable stabilization strategy that enhances infrastructure resilience and promotes circular economy objectives.

Song Zhao, Jian Ouyang, Wenting Yang

Zhenjie Lun, Minbo Wu, Di Zuo et al.

The intricate amorphous structure and elusive local environment of rare-earth (RE) doped laser glasses render existing physical or machine-learning models inadequate for guiding the design of next-generation laser glasses, thereby maintaining iterative experimentation as the primary method for development. Here, the microenvironment surrounding RE ions in a multicomponent laser glass is treated as a statistical ensemble derived from its neighboring glassy compounds (NGCs). The NGCs model employs statistical ensemble averaging over the NGCs to provide a rigorous mathematical description of the key local structural and luminescent behaviors of RE-doped laser glasses. Validation through molecular dynamics simulations and experimental data for quaternary germanate glass system demonstrates the model’s excellent predictive capabilities, allowing it to establish the composition–structure relationship and populate the composition–property space. Moreover, the model enables the creation of multi-luminescence property charts, facilitating the de novo design of chemically complex laser glasses for targeted applications by efficiently screening the compositions which simultaneously meet several performance constraints. This work offers a robust framework for studying the luminescent behaviors of glass and paves the way for new explorations in laser glass technology.

Puput Risdanareni, Vita Ayu Kusuma Dewi, Ruri Agung Wahyuono et al.

Hydrogel-based self-healing mortar often experiences strength decrease that may impact concrete performance under mechanical load. While the addition of commercial colloidal nano silica can improve the strength of hydrogel-based self-healing mortar, they can be relatively expensive. This work examines the synthesis of an alternative and affordable nano-silica, aiming to improve the mechanical strength of hydrogel-based self-healing mortar. Nano silica is extracted from abundantly available mineral admixture, i.e., fly ash through chemical purification methods. Two concentrations of 2 % and 5 % nano silica by mass replacement of cement are used in the mortar mixture. X-ray diffraction was conducted to ensure that nano silica produced is in amorphous form. The hydration kinetics of resulting paste, workability, compressive strength, healing capacity and capillary water absorption of resulting mortar were investigated. The results prove the production of high-quality nano silica from fly ash with sufficient amorphous phase. The hydration kinetics indicate that the incorporation of nano-silica derived from fly ash at a dosage of 2 % accelerates the hydration reaction. This acceleration corresponds with the observed enhancement in the compressive strength of hydrogel-loaded mortar, where the addition of 2 % nano-silica fly ash produced strength values comparable to those of the reference sample while maintaining the self-healing capability. Therefore, a dosage of 2 % nano-silica fly ash by cement weight is recommended as an effective mineral additive for improving the mechanical performance of hydrogel-based self-healing mortars.

Chidiebere I. Nwaogbo, Sanjib K. Das, Chinedu E. Ekuma

We investigate the topological properties of the vanadium-based 2D kagome metal ScV$_6$Sn$_6$, a ferromagnetic material with a magnetic moment of 0.86 $μ_B$ per atom. Using ab initio methods, we explore spin-orbit coupling-induced gapped states and identify multiple Weyl-like crossings around the Fermi energy, confirming a Chern number $|C| = 1$ and a large anomalous Hall effect (AHE) of 257 $Ω^{-1}$cm$^{-1}$. Our calculations reveal a transition from a topological semimetal to a trivial metallic phase at an electric field strength of $\approx$0.40 eV/Å. These findings position 2D ScV$_6$Sn$_6$ as a promising candidate for applications in modern electronic devices, with its tunable topological phases offering the potential for future innovations in quantum computing and material design.

K. Lizárraga, J. A. Guerra, L. A. Enrique-Moran et al.

Accurate determination of the exciton binding energy and reduced effective mass in halide perovskites is of utmost importance for the selective design of optoelectronic devices. Although these properties are currently determined by several spectroscopic techniques, complementary theoretical models are often required to bridge macroscopic and microscopic properties. Here, we present a novel method to determine these quantities while fully accounting for polarization effects due to carrier interactions with longitudinal optical phonons. Our approach estimates the exciton-polaron binding energy from optical absorption measurements using a recently developed Elliott based Band Fluctuations model. The reduced effective mass is obtained via the Pollmann-Buttner exciton-polaron model, which is based on the Frohlich polaron framework, where the strength of the electron-phonon interaction arises from changes in the dielectric properties. The procedure is applied to the family of perovskites ABX3 (A = MA, FA, Cs; B = Pb; X = I, Br, Cl), showing excellent agreement with high field magnetoabsorption and other optical-resolved techniques. The results suggest that the Pollmann-Buttner model offers a robust and novel approach for determining the reduced effective mass in metal tri-halide perovskites and other polar materials exhibiting free exciton bands.

Heydar Dehghanpour, Serkan Subasi, Sefa Guntepe et al.

Min Hao, Wenhan Wang, Anil Kumar et al.

Abstract The low survival rate and poor differentiation efficiency of stem cells, as well as the insufficient integration of implanted stem cells, limit the regeneration of bone defects. Here, we have developed magnetic ferroferric oxide‐hydroxyapatite‐polydopamine (Fe3O4‐HAp‐PDA) nanobelts to assemble mesenchymal stem cells (MSCs) into a three‐dimensional hybrid spheroid for patterning bone tissue. These nanobelts, which are featured by their high‐aspect ratio and contain Fe3O4 nanospheres with a PDA coating, can be manipulated by a magnetic field and foster enhanced cell‐nanobelt interactions. This strategy has been demonstrated to be effective for both bone marrow mesenchymal stem cells and adipose‐derived mesenchymal stem cells, enabling remote manipulation of stem cell spheroids and efficient spheroid fusion, which in turn accelerates osteogenic differentiation. Consequently, this methodology serves as an efficient and general tool for bone tissue printing and can potentially overcome the low survival rate and poor differentiation efficiency of stem cells, as well as mismatched interface fusion issues.

Hui Wang, Zhe Lv, Huanyong Cui et al.

Abrasive waterjet peening is a favorable surface treatment method for improving the fatigue resistance of metal materials. An insight into the fatigue crack growth properties of AWJ peened specimens is meaningful for obtaining better strengthening performance. In present work, a numerical model of AWJ peening was established and experimentally validated for investigating the fatigue crack growth characteristics of Aluminum specimens. The effect of peening and loading conditions on the fatigue performance was also analyzed. The results indicated that the stress intensity factor at the peened region was enhanced and the crack propagation was significantly inhibited by the compressive residual stress. The influence of compressive residual stress on the effective stress factor range is greater under lower external load and higher loading ratio. The fatigue life for reaching the crack length of 40 mm is increased by 37%, 60% and 98% after peening by using the intensity of 0.6 mmA, 0.8 mmA and 1 mmA, respectively.

Murat Doğruyol, Ersin Ayhan, Abdulhalim Karaşin

Recently, recycling of waste vehicle tyres which pose a significant risk to environmental health has become an important research issue due to environmental concerns worldwide. To handle the waste tyre pollution problem, recycling waste into new products and using waste to improve other materials’ properties can be considered. Waste vehicle tyres can be used in the production of energy and various materials, providing economic and environmental advantages. In this study, experimental studies were carried out on the use of waste tyre steel fiber (WS) obtained from the recycling of heavy vehicle tyres in concrete, including the goal of recycling and reducing the need for raw materials. In one experimental group, waste tyre steel was added to concrete at 0.4% by volume instead of fine aggregate, while in the other experimental group it was added at 0.8% by volume. In the study, in addition to mechanical analyses, many microanalysis experiments were carried out to understand whether there was a strong relationship between the results. The study was conducted at target temperatures of 400, 600 and 800 °C depending on the fire scenario for building and construction materials according to ISO 834 and ASTM E119 standards. Compressive strength losses and characterization changes in 15 cm cube plain concrete and composite concrete specimens exposed to targeted high temperatures for 60 minutes were compared in terms of strength. Ultrasonic pulse velocity (UPV), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis was also performed, as it was understood that there was not enough data in the literature regarding waste tyre steel fiber reinforced concrete. General results showed that fiber-added concrete made significant contributions to concrete performance at high temperatures.

Yasuko Kawahata

This study delves into the intricate electronic and optical behaviors of two-dimensional (2D) honeycomb materials, such as Stannen, arsenene, antimonene, silicene, and bismuthene(bismuth molecule), through the lens of first-principles calculations(AB Initio Calculations) based on the Kohn-Sham equations. Focusing on the exchange-correlation potential approximations within the Density Functional Theory (DFT) framework, we evaluate the potential of these materials in digital information control and management. Special attention is given to the nonlinear optical responses and electronic properties under the influence of twisted bilayer configurations, external fields, and varying twist angles. The findings offer novel insights into the design of advanced digital devices, suggesting a transformative approach to information technology through the utilization of 2D honeycomb materials.

Sajjad Pashazadeh, Alexandra Aulova, Christos K. Georgantopoulos et al.

Abstract The present study highlights a range of surface and volume extrudate patterns that can be detected during the extrusion flow of long‐chain branched polymers. Thus, four linear low‐density polyethylenes (LDPEs) have been extruded using a single‐screw extruder coupled to an inline optical imaging system. The selected LDPEs are selected to outline the influence of molecular weight and long‐chain branching on the types of melt flow extrusion instabilities (MFEI). Through the inline imaging system, space–time diagrams are constructed and analyzed via Fourier‐transformation using a custom moving window procedure. Based on the number of characteristic frequencies, peak broadness, and whether they are surface or volume distortions, three main MFEI types, distinct from those typically observed in linear and short‐chain branched polymers, are identified. The higher molecular weight, low long‐chain branching LDPEs exhibited all three instability types, including a special type volume instability. Independently of the molecular weight, higher long‐chain branching appeared to have a stabilizing effect on the transition sequences by suppressing volume extrudate distortions or limiting surface patters to a form of weak intensity type.

James A. D. Ball, Jette Oddershede, Claire Davis et al.

The ability to characterise the three-dimensional microstructure of multiphase materials is essential for understanding the interaction between phases and associated materials properties. Here, laboratory-based diffraction-contrast tomography (DCT), a recently-established materials characterization technique that can determine grain phases, morphologies, positions and orientations in a voxel-based reconstruction method, was used to map part of a dual-phase steel alloy sample. To assess the resulting microstructures that were produced by the DCT technique, an EBSD map was collected within the same sample volume. To identify the 2D slice of the 3D DCT reconstruction that best corresponded to the EBSD map, a novel registration technique based solely on grain-averaged orientations was developed -- this registration technique requires very little a priori knowledge of dataset alignment and can be extended to other techniques that only recover grain-averaged orientation data such as far-field 3D X-ray diffraction microscopy. Once the corresponding 2D slice was identified in the DCT dataset, comparisons of phase balance, grain size, shape and texture were performed between DCT and EBSD techniques. More complicated aspects of the microstructural morphology such as grain boundary shape and grains less than a critical size were poorly reproduced by the DCT reconstruction, primarily due to the difference in resolutions of the technique compared with EBSD. However, lab-based DCT is shown to accurately determine the centre-of-mass position, orientation, and size of the large grains for each phase present, austenite and martensitic ferrite. The results reveals a complex ferrite grain network of similar crystal orientations that are absent from the EBSD dataset. Such detail demonstrates that lab-based DCT, as a technique, shows great promise in the field of multi-phase material characterization.

Gieberth Rodriguez-Lopez, Kirsten Martens, Ezequiel E. Ferrero

We examine the structural relaxation of glassy materials at finite temperatures, considering the effect of activated rearrangements and long-range elastic interactions. Our three-dimensional mesoscopic relaxation model shows how the displacements induced by localized relaxation events can result in faster-than-exponential relaxation. Thermal activation allows for local rearrangements, which generate elastic responses and possibly cascades of new relaxation events. To study the interplay between this elastically-dominated and thermally-dominated dynamics, we introduce tracer particles that follow the displacement field induced by the local relaxation events and also incorporate Brownian motion. Our results reveal that the dynamic exponents and shape parameter of the dynamical structure factor depend on this competition and display a crossover from faster-than-exponential to exponential relaxation as temperature increases, consistent with recent observations in metallic glasses. Additionally, we find the distribution of waiting times between activations to be broadly distributed at low temperatures, providing a measure of dynamical heterogeneities characteristic for to glassy dynamics.

Nikita Medvedev

This proceeding discusses the impact of XUV/X-ray irradiation on materials, and how their response is affected by temperature, size, and structure. When materials are exposed to intense XUV/X-ray irradiation, they undergo a series of processes ultimately leading to observable structure modification and damage. These effects were studied with a hybrid simulation tool XTANT-3. The code combines several methods in one interconnected model: the photon absorption and electron cascades are simulated with transport Monte Carlo; nonequilibrium kinetics of slow electrons (in the valence and the bottom of the conduction band) is traced with the Boltzmann equation; modeling evolution of the electronic structure and interatomic potential is done with the transferable tight binding method; and the response of the atomic system is simulated with the molecular dynamics. Combining these methods enabled the tracing of the essential effects of irradiation. This brief review summarizes the recent results obtained with this simulation tool.

Nikolay Aniskin, Aleksey Shaytanov, Mikhail Shaytanov

In this paper, we consider the issue of assessing the degree of influence of the selected factors on the temperature regime and the thermally stressed state of a concrete gravity dam being built from low-cement concrete for several possible construction scenarios. The studies were carried out in relation to the design and conditions of the construction area of ​​the Pskem hydroelectric complex in the Republic of Uzbekistan. Variation factors were: cement consumption in the mixture, the initial temperature of the concrete mixture, the heat release of cement, the thickness of the laid concrete layer, the month of commencement of work. The environmental factors were the variable ambient temperature during the year by months and the influence of solar radiation. The calculations were carried out taking into account the seasonality of the moment the construction of the structure began. 2 options were considered: autumn-winter with concreting of the zone at the base of the dam from September to February inclusive; spring-summer with concreting of this zone from March to August inclusive. In addition, options were considered taking into account additional heating from exposure to solar radiation and without it. The studies were carried out using the methodology of experiment planning in the search for optimal solutions (method of factor analysis). The numerical experiment was carried out on the basis of the finite element method using the ANSYS software package. Using the method of factor analysis, the influence of the main acting factors on the temperature regime of a gravity dam made of rolled concrete was studied. A variant of a combination of factors is proposed to obtain the most favorable temperature regime. Regression equations are obtained for predicting the temperature regime of concrete gravity dams being built from low-cement content concrete. The results of studies using the factor analysis technique can be used in the design of concrete dams from rolled concrete.

Ji Wang, Rui Shu, Jianlong Chai et al.

The study aims to understand the irradiation behavior of multilayer coatings composed of high-entropy materials. Here, we report the structural stability and elemental segregation of high-entropy TiNbZrTa/CrFeCoNi metallic and nitride multilayer coatings under 3-MeV Xe20+ ion-irradiation at room temperature and 500 °C, respectively. Transmission electron microscopy analysis shows that the microstructure of nanocrystalline CrFeCoNi high-entropy-alloy sublayers are not stable and readily transforms into amorphous state at 500 °C and/or under irradiation conditions. The elemental distribution, acquired by energy-dispersive X-ray spectroscopy under scanning transmission electron microscopy mode, shows preferential diffusion of Co and Ni into TiNbZrTa sublayers, while Fe and Cr preferentially remain within the previous CrFeCoNi sublayers. TiNbZrTaN/CrFeCoNiNx nitride multilayers exhibit a higher crystallinity and structural stability as well as resistance to diffusion at high-temperature and/or irradiation conditions than their TiNbZrTa/CrFeCoNi metallic multilayer counterparts. These findings are explained by atomic size differences, the difference in Gibbs free energy of the mixing system, and interstitial-solute-induced chemical heterogeneity. Our findings thus provide a design strategy of high entropy nitride for nuclear fuel cladding.

Laisi Chen, Amy X. Wu, Naol Tulu et al.

Confining materials to two-dimensional forms changes the behavior of electrons and enables new devices. However, most materials are challenging to produce as uniform thin crystals. Here, we present a new synthesis approach where crystals are grown in a nanoscale mold defined by atomically-flat van der Waals (vdW) materials. By heating and compressing bismuth in a vdW mold made of hexagonal boron nitride (hBN), we grow ultraflat bismuth crystals less than 10 nanometers thick. Due to quantum confinement, the bismuth bulk states are gapped, isolating intrinsic Rashba surface states for transport studies. The vdW-molded bismuth shows exceptional electronic transport, enabling the observation of Shubnikov-de Haas quantum oscillations originating from the (111) surface state Landau levels, which have eluded previous studies. By measuring the gate-dependent magnetoresistance, we observe multi-carrier quantum oscillations and Landau level splitting, with features originating from both the top and bottom surfaces. Our vdW-mold growth technique establishes a platform for electronic studies and control of bismuth's Rashba surface states and topological boundary modes. Beyond bismuth, the vdW-molding approach provides a low-cost way to synthesize ultrathin crystals and directly integrate them into a vdW heterostructure.

Jiayin Chen, Wei Zhang, Haoze Li et al.

Abstract Nitrogen (N2) fixation under mild conditions is a promising approach for green production of ammonia (NH3). In the past decades, various advanced catalysts have been fabricated to achieve this goal through electrocatalytic and photocatalytic processes. Among them, the TiO2‐based catalysts have been recognized as promising candidates due to their high activity, low cost, chemical stability, and nontoxicity. In this review, recent advances in the fabrication of high‐performance TiO2‐based materials for N2 reduction reaction (NRR) under mild conditions are summarized, including electrocatalytic and photocatalytic NRR. The design principles, synthetic strategies, and corresponding chemical/physical properties of TiO2‐based NRR catalysts are described in detail. Moreover, the key challenges and potential opportunities in this field are presented and discussed.

Shanshan Gao, Weixue Li, Jianfeng Dai et al.

The effects of transition metal (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) doping on the stability, electronic structure and optical properties of β -Ga _2 O _3 have been studied using GGA and GGA + U. The results show that the U value can correct the strong interaction of the d-layer, causing orbital hybridization and affecting the position and number of impurity energy levels. It can move the conduction band to higher energy levels and weaken the role of Ga-3p in the valence band. The Ti-doped β -Ga _2 O _3 is easily formed, followed by V, Cr, Sc, Fe, Mn, Co, Ni, Cu, and Zn doping. Some bands change regularly with the increase of atomic number. All systems become degraded semiconductors after doping. All doping will make the β -Ga _2 O _3 red shift. Among them, the absorption intensity of Cu doping in the visible light range is significantly improved.