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

Kyriakos Komvopoulos

Bappy Sen, Hemen Sarma

Abstract Carbon quantum dots (CQDs) have emerged as highly promising multifunctional nanomaterials for next-generation optoelectronic applications, offering tunable fluorescence, high biocompatibility, and sustainable synthesis routes. In this review, we explore recent advances in CQD-based fluorescent biosensors, emphasizing their potential in real-time pollutant detection, bioimaging, and green energy solutions. We analyze the underlying photophysical mechanisms, including quantum confinement, surface functionalization, and heteroatom doping, that govern fluorescence modulation. Importantly, the review highlights eco-friendly synthesis techniques and the integration of CQDs in optoelectronic architectures such as photodetectors, photocatalytic systems, and hybrid sensors. By coupling photonic and electronic responses within a single material platform, CQDs offer a pathway toward energy-efficient, neuromorphic-inspired sensing and processing. We conclude by identifying future directions for enhancing the multifunctionality, spectral selectivity, and device-level integration of CQDs, positioning them as sustainable alternatives in two-dimensional (2D) optoelectronic systems.

Di Wang, Catriona M McGilvery, James O Douglas et al.

Hafnium hydride is a promising material for next-generation nuclear reactors, particularly as control rods for fast fission and shielding in fusion systems. The material's intrinsic brittleness encourages its use in the form of hydride-metal composites, where the functional and mechanical performance is strongly influenced by the multiscale structure of hydride-matrix interfaces. In this study, we employ a suite of microscopy techniques, including scanning electron microscopy with electron backscatter diffraction, transmission electron microscopy with electron energy-loss spectroscopy, and atom probe tomography, to investigate the deuteride-matrix interfaces in a deuterium-charged Hf alloy. We characterise their structure and chemistry, extracting key information including the deuteride-matrix crystallographic orientation relationship, microstructural features, misfit-induced dislocation distributions, electron energy-loss characteristics, and the segregation of oxygen during deuteride growth. These findings help clarify the mechanisms of interface evolution and may contribute to improved understanding of hydride-metal systems, with potential relevance for their processing, performance, and design in nuclear applications.

Hao Yang, Fujie Zhao, Junhui Zhang et al.

Kyle D. Miller, Michele Campbell, Danilo Puggioni et al.

We introduce decoratypes as a structure taxonomy that classifies compounds based on site decorations of specific structural prototypes. Building on this foundation, a ferroelectric materials discovery framework is developed, integrating decoratypes with an active learning approach to accelerate exploration. In addition, six novel ferroelectric candidates are predicted, including three strain-activated ferroelectrics and three strain-activated hyperferroelectrics. These findings highlight the potential of the decoratype taxonomy to enhance our understanding of structure-driven material properties and facilitate the discovery of promising yet underexplored regions of chemical space.

GONG Xuan, LIU Jiachen, CUI Yan, LI Qiang

In order to enhance the wear resistance of aluminum alloy surfaces，Ni-P/diamond composite coatings were prepared on 2014 aluminum alloy surfaces using electroplating method.The effects of varying diamond particle content in the coating on the coating’s elemental composition， surface morphology， microhardness， corrosion resistance and wear resistance were investigated using wavelength dispersive X-ray fluorescence spectroscopy， scanning electron microscopy (SEM)， Vickers hardness testing， electrochemical workstation and friction-wear testing machine.Results showed that as the concentration of diamond particles in the plating solution increased from 0 to 1.0 g/L，the corrosion current density decreased and the corrosion potential increased.The micro Vickers hardness improved from 526 to 786 HV0.5.When the diamond particle concentration was 1.0 g/L， the coating exhibited the lowest wear rate.With the increase in diamond content， the wear mechanism of the coating transitioned from fatigue wear to a combination of fatigue and adhesive wear， eventually shifting to predominantly adhesive wear.

Reshma Devi, Keith T. Butler, Gopalakrishnan Sai Gautam

Abstract A pathway to overcome limited data availability in materials science is to use the framework of transfer learning, where a pre-trained (PT) machine learning model (on a larger dataset) can be fine-tuned (FT) on a target (smaller) dataset. We systematically explore the effectiveness of various PT/FT strategies to learn and predict material properties and create generalizable models by PT on multiple properties (MPT) simultaneously. Specifically, we leverage graph neural networks (GNNs) to PT/FT on seven diverse curated materials datasets, with sizes ranging from 941 to 132,752. Besides identifying optimal PT/FT strategies and hyperparameters, we find our pair-wise PT-FT models to consistently outperform models trained from scratch on target datasets. Importantly, our MPT models outperform pair-wise models on several datasets and, more significantly, on a 2D material band gap dataset that is completely out-of-domain. Finally, we expect our PT/FT and MPT frameworks to accelerate materials design and discovery for various applications.

M H Qureshi, A Farooq, M Wasim et al.

The Al-Zn sacrificial anodes are widely used for cathodic protection in marine steel structures. This study evaluates the impact of bismuth addition on the electrochemical properties of the Al-Zn sacrificial anode in artificial seawater. The microstructure analysis confirms the presence of uniformly distributed intermetallic β -AlFeSi and spherical Bi within the α -Al matrix. The open circuit potential (OCP) comparison between Al-Zn-Bi and carbon steel reveals a potential difference of approximately 400 mV, indicating sufficient cathodic protection for the steel. Electrochemical impedance measurements indicate the initial hindered dissolution of the anode due to surface film formation, which later dissociates due to the aggressive attack of Cl ^− species in the electrolyte. The sufficiently negative surface potential (−0.875 V _vs. Ag/AgCl ) observed at 10 mA cm ^−2 demonstrates the suitability of anode for fulfilling the cathodic protection criteria of steel structures.

Younghun Shin, Kwon-Yeong Lee, Jeong-Won Lee et al.

Condensation refers to the change of a substance from a gaseous phase to a liquid phase, an example of which is the condensation of water vapor in nature. Condensation is used in many industries, such as energy generation and seawater desalination. On a general surface, filmwise condensation is the main phenomenon in which gaseous water vapor is condensed in the form of a film. However, film condensation acts as a factor that reduces energy efficiency as the liquid film formed on the surface interferes with heat transfer. A phenomenon opposite to film condensation is dropwise condensation, which is immediately separated after condensation in the form of droplets, and thus a film is not formed, greatly improving heat transfer efficiency. Because of these advantages, many studies have been conducted, and most studies have induced dropwise condensation by modifying the surface to be superhydrophobic. However, in the case of a superhydrophobic surface, it takes a lot of time and money in the process, so there is a great difficulty in increasing the area. Among them, stainless steel and titanium, which are most materials for industrial heat exchangers, have high robustness, so there are few studies on improving the condensation performance after surface modification due to the difficulty of processing. For this reason, there is a large gap between the currently conducted studies and the actual industry. Our research team succeeded in modifying the surface of a stainless steel and titanium tube the size of an actual heat exchanger into superhydrophobicity with a simple process. We confirmed that the condensation performance was improved on the superhydrophobic surface through experiments under various conditions. By comparing the improvement in the heat transfer performance of stainless steel and titanium under several conditions, the main cause of the performance improvement was proved. This study is expected to play a major role in the eco-friendly future industry where energy efficiency is important by improving the heat transfer performance of stainless steel and titanium, which are mainly used throughout the industry.

Siming Liang, Yuhang Liu, Guofeng Song et al.

Incorporating a suitable amount of sulfoaluminate expansive additive (SEA) into cementitious materials can compensate the shrinkage deformation. However, the influence of SEA on the relative humidity inside cementitious materials is still unclear. This study conducted a series of tests to investigate the mechanical properties, internal relative humidity, and shrinkage of early-age cement mortars containing different contents of SEA. Then finite element simulations of the drying of cement mortars with different contents of SEA were conducted to derive the moisture diffusion coefficient. The results reveal that the amount of expansive ettringite generated in cement mortar tends to increase with increasing SEA content, which can decrease the porosity of cement mortar and refine its pore structures. Both the compressive strength and flexural strength of cement mortar decrease with increasing SEA content. The decrease in mortar strengths is more significant during the later age. The mortar shrinkage under both sealed and drying conditions decreases with increasing SEA content. However, the compensation effect of SEA on the shrinkage deformation is less effective under drying condition. The relative humidity inside the cement mortar under sealed condition would decrease by 9.3% at 36 days when 8% SEA was used. While the decrease would be 3.4∼7.2% when the cement mortar was exposed to drying condition with RH of 60%. Moreover, since SEA densifies the microstructures and refines the pores in mortar, the moisture diffusion coefficient of mortar decreases with increasing SEA content.

I. Pallecchi, F. Caglieris, M. Ceccardi et al.

The family of Van der Waals dichalcogenides (VdWDs) includes a large number of compositions and phases, exhibiting varied properties and functionalities. They have opened up a novel electronics of two-dimensional materials, characterized by higher integration and interfaces which are atomically sharper and cleaner than conventional electronics. Among these functionalities, some VdWDs possess remarkable thermoelectric properties. SnSe2 has been identified as a promising thermoelectric material on the basis of its estimated electronic and transport properties. In this work we carry out experimental meas-urements of the electric and thermoelectric properties of SnSe2 flakes. For a 30 micron thick SnSe2 flake at room temperature, we measure electron mobility of 40 cm^2 V^-1 s^-1, a carrier density of 4 x 10^18 cm^-3, a Seebeck coefficient S around -400 microV/K and thermoelectric power factor around 0.35 mW m^-1 K^-2. The comparison of experimental results with theoretical calculations shows fair agreement and indicates that the dominant carrier scattering mechanisms are polar optical phonons at room temperature and ionized im-purities below 50 K. In order to explore possible improvement of the thermoelectric properties, we carry out reversible electrostatic doping on a thinner flake, in a field effect setup. On this 75 nm thick SnSe2 flake, we measure a field effect variation of the Seebeck coefficient of up to 290 % at low temperature, and a corresponding variation of the thermoelectric power factor of up to 1050 %. We find that the power factor increases with the depletion of n-type charge carriers. Field effect control of thermoelectric transport opens perspectives for boosting energy harvesting and novel switching technologies based on two-dimensional materials.

Zejia Zhao, Suet To, Jingwei Wang et al.

Metallic materials have long been used in a wide range of industrial applications due to their outstanding physical and mechanical properties as well as high process latitudes. Mechanical machining is one of the important steps in manufacturing of metallic components because it directly influences the surface quality of the final products. To date, extensive studies have been conducted on the investigation of factors affecting the machinability of metallic materials, such as cutting parameters, cooling conditions and material micro/nanostructures. Contributory factors of cutting parameters and cooling conditions have been extensively reviewed in previous studies, but there is still a lack of a fundamental review to clearly understand the effects of material micro/nanostructures on the machining. Therefore, this review highlights the influences of different micro/nanostructures on the machinability and discusses the materials deformation mechanism in machining of metallic materials. The micro/nanostructures mainly include crystalline anisotropies of single crystals, grain sizes of polycrystals, phase compositions of single/multiphase materials, layer-by-layer structures of additive manufactured materials, amorphous structures of bulk metal glasses, micro reinforcements of metal matrix composites, and porosities of porous metal foams. Besides, the challenges and opportunities faced in machining of metallic materials are discussed from the perspective of micro/nanostructures.

Nikita Medvedev, Zuzana Kuglerová, Mikako Makita et al.

Materials exposed to ultrashort intense x-ray irradiation may experience various damaging conditions depending on the in-situ temperature. A pre-heated target exposed to intense x-rays plays a crucial role in numerous systems of physical-technical importance, ranging from the heavily-, and repeatedly radiation-loaded optics at x-ray free-electron laser facilities, to the first wall of prospective inertial fusion reactors. We study theoretically the damage threshold dependence on the temperature in different classes of materials: an insulator (diamond), a semiconductor (silicon), a metal (tungsten), and an organic polymer (PMMA). The numerical techniques used here enable us to trace the evolution of both, an electronic state and atomic dynamics of the materials. It includes damage mechanisms such as thermal damage (induced by an increase of the atomic temperature due to energy transfer from x-ray-excited electrons) and nonthermal phase transitions (induced by changes in the interatomic potential due to excitation of electrons). We demonstrate that in the pre-heated materials, typically, the thermal damage threshold stays the same or lowers with the increase of the in-situ temperature, whereas nonthermal damage thresholds may be lowered or raised, depending on the particular material and specifics of the damage kinetics.

Z. Saki, H. Azizi, I. Ghasemi et al.

In the current research, to develop the morphology and improvement of electrical conductivity at low levels of graphene nanoplates (GNPs); the effect of polyolefin elastomer (POE) and graphene content on morphology, mechanical and electrical properties of polylactic acid (PLA) was investigated. Different Blends with and without compatibilizer were prepared via melt mixing process in an internal mixer through masterbatch approach. Co-continuous morphology was obtained at the ratio of 60/40 (wt%/wt%) of PLA/POE. By considering the wetting coefficient, it was predicted that graphene nanoplates have more affinity to the POE phase than PLA, which was confirmed by microscopic observations. The electrical percolation threshold was seen at 0.5–1 wt% of graphene, while the rheological percolation threshold was obtained at 0.2–0.5 wt%. The addition of POE and graphene to PLA led to balancing elongation at break and tensile strength of final products.

Luis Casillas-Trujillo, Rickard Armiento, Björn Alling

Important phenomena such as magnetostriction, magnetocaloric, and magnetoelectric effects arise from, or could be enhanced by, the coupling of magnetic and structural degrees of freedom. The coupling of spin and lattice also influence transport and structural properties in magnetic materials in particular around phase transitions. In this paper we propose a method for screening materials for a strong magneto-structural coupling by assessing the effect of the local magnetic configuration on the atomic forces using density functional theory (DFT). We have employed the disordered local moment approach in a supercell formulation to probe different magnetic local configurations and their forces and performed a high-throughput search on binary and ternary compounds available in the Crystallographic Open Database. We identify a list of materials with a strong spin-lattice coupling out of which several are already known to display magneto-lattice coupling-phenomena like Fe3O4 and CrN. Others, such as Mn2CrO4 and CaFe7O11 have been less studied and are yet to reveal their potentials in experiments and applications.

Wenjing Zhao, Hongxia Yang, Zhihui Li et al.

This work reports that the polyvinyl alcohol successfully templates the intracrystal mesoporous structure of hierarchical SAPO-11 molecular sieves. The structures of prepared hierarchical SAPO-11 materials and a conventional SAPO-11 simultaneously synthesized are characterized by X-ray diffraction, N _2 adsorption/desorption, scanning electron microscopy and high resolution transmission electron microscopy. The characterizations demonstrate that this synthesized hierarchical SAPO-11 possesses a mesopore structure with a much regular pore size distribution. Importantly, these mesopores are intracrystal but not intercrystal. The bifuntional isomerization catalyst with this hierarchical SAPO-11 as support shows a high selectivity in hydroisomerization reaction of hexane, evidencing that the catalytic selectivity is improved by introduction of mesopore structure into the SAPO-11 crystal. The templating mechanism of polyvinyl alcohol in formation of mesopores is well discussed at the ending. This work provides a potential template to prepare hierarchical catalyst materials.

T. Balawender, M. Zwolak, Ł. Bąk

The paper presents selected results of KOBO extrusion process of circular profile ϕ10 mm from aluminum alloy 2099. The main aim of the performed research was to determine the influence of the oscillation frequency of a die on the magnitude of extrusion force. During the process such parameters, as extrusion force, rate of stem and frequency of die oscillation were recorded; oscillating angle of a die was constant and equal ±8°. The die oscillation frequency was changeable in performed tests in the range of 2 ÷ 7 Hz. The obtained results allowed to determine the relation between the maximum extrusion force and the die oscillation frequency during extrusion of aluminum 2099 alloy. The paper focuses on the experimental analysis of mechanical characteristics of the KOBO process. Basing on the recorded force versus stem position, three stages of KOBO extrusion process were determined, i.e. initialization, stabilization and uniform extrusion. Points separating these stages are two inflection points of recorded diagram. The analysis of each stage was made basing on the results of force diagrams and literature data.

Sendong Ren, Yunwu Ma, Shuhei Saeki et al.

Carbon fiber reinforced plastic (CFRP) is a prospective lightweight material in automobile industry. However, joining metal and CFRP is a great challenge. In the present study, an innovative process called coaxial one-side resistance spot welding (COS-RSW) is proposed to fabricate Al5052 (Al) and CFRP joints. Based upon our newly developed finite element code JWRIAN, the electric-thermal-mechanical coupled process of COS-RSW is modeled and validated with experiments. The influences of welding current, welding time and electrode force on CFRP molten zone are investigated in detail. The results show that the depth of molten zone has a strong correlation with both welding current and welding time. A relative low welding current or short welding time that results in the Al/CFRP interface temperature below the melting temperature of the resin matrix is insufficient to form a sound connection between the two sheets. While excessive current or too long welding time may lead to overheating of CFRP and decomposition of the resin matrix, which increases the risk of weak joining. Furthermore, it is found that the depth of molten zone increases even at the cooling stage, which indicates accurate simulation for both the heating and the cooling stages of the COS-RSW process is indispensable. Keywords: Coaxial one-side resistance spot welding, Carbon fiber reinforced plastic, Al5052, Dissimilar materials, Multiphysics coupling simulation

Shreshth A. Malik, Rhys E. A. Goodall, Alpha A. Lee

A common bottleneck for materials discovery is synthesis. While recent methodological advances have resulted in major improvements in the ability to predicatively design novel materials, researchers often still rely on trial-and-error approaches for determining synthesis procedures. In this work, we develop a model that predicts the major product of solid-state reactions. The cardinal feature of this approach is the construction of fixed-length, learned representations of reactions. Precursors are represented as nodes on a `reaction graph', and message-passing operations between nodes are used to embody the interactions between precursors in the reaction mixture. Through an ablation study, it is shown that this framework not only outperforms less physically-motivated baseline methods but also more reliably assesses the uncertainty in its predictions.