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Systematic study on the microstructural evolution, interfacial diffusion and mechanical properties of ultra-thin stainless steel–copper composites (50 µm) after annealing treatment was conducted in the present study. The results show that the as-received specimen exhibits low elongation (0.031) as well as high strength (891.346 MPa) by work hardening, thus requires heat treatment to improve the plasticity. With the increase of annealing temperature from 700 to 1000 °C, the dislocation/grain boundary strengthening is weakened while the surface grains which exhibit fewer constraints is increasing, resulting in lower strength. Moreover, a uniform and refined microstructure with high recrystallization rate is formed inside stainless steel and copper matrixes for the specimens annealed at 900 °C, thereby improving the plasticity of ultra-thin stainless steel–copper composites. Additionally, an obvious strain gradient exists at the interface of ultra-thin stainless steel–copper composites, and the interdiffusion process between stainless steel and copper matrixes is primarily governed by the diffusion of Cu atoms. The influence of diffusion layer thickness on the strength of ultra-thin stainless steel–copper composites is negligible. Overall, an optimal annealing temperature of 900 °C is obtained with the improved plasticity of ultra-thin stainless steel–copper composites. [ABSTRACT FROM AUTHOR]

The fatigue of adhesive joints in offshore wind turbine blades is a critical and widespread challenge, necessitating an urgent focus on adhesive bond reliability. Given the constraints of full-scale testing, this research explores the fatigue endurance of carbon fiber–epoxy adhesive composites, integral to blade construction. Recognizing the fatigue characteristics' sensitivity to environmental factors and joint dimensions, an innovative approach to fatigue modelling and evaluation is introduced. This method incorporates the influence of different environmental stresses and size effects. Specifically, a degradation coefficient and size impact factor (SIF) are introduced into the cyclic cohesive zone model, and a simulation-based analytic approach is proposed for analyzing adhesive fatigue. Furthermore, we introduce a reliability modelling procedure that integrates performance degradation theory to address the deteriorative characteristics inherent in adhesive fatigue. Subsequently, the specimens' damage accumulation increased by 75% because of the stresses and escalated to 85% with adhesive joint size effects, causing carbon fiber Reinforced Polymer/epoxy adhesive joints to fail interfacially rather than in a mixed-mode manner. This study provides valuable insights for the safety analysis and assessment of adhesive joint performance in offshore wind turbine blades. [ABSTRACT FROM AUTHOR]

Dams fragment stream habitats and fishways around dams typically serve few species that are strong swimmers or jumpers. We tested a prototype wetted ramp designed to allow upstream passage of small-bodied fishes while blocking upstream movement of invasive sea lampreys in the Laurentian Great Lakes. We tested short, smooth ramps with 5–10 mm water depth in various combinations of ramp angle, water flow, and swim channel width with the aim to selectively block adult migrating sea lampreys (Petromyzon marinus) while passing sub-adult white suckers (Catostomus commersonii) and creek chubs (Semotilus atromaculatus). Sea lampreys easily passed a 0.75 ramp at a 5° angle, but very few individuals passed a similar ramp at a 10° angle, and none passed a longer ramp at a 5° angle. Limiting the amplitude of tailbeats in a narrow channel did not hamper lampreys or the other species. Greater water flow, and thereby greater immersion depth on the ramp, fostered passage for all species. Smaller-bodied individuals of creek chubs and white suckers performed best on the ramp. We showed that wetted ramps could be incorporated into fishways at low-head dams to aid the passage of smaller-bodied fishes while also blocking the spawning migration of adult sea lampreys. [ABSTRACT FROM AUTHOR]

Non-uniform deformation of the dielectric subjected to external forces can induce the flexoelectric effect, a phenomenon that couples electrical polarization to strain gradients. However, limited by the size effects, flexoelectricity is not significant at the macroscale and only becomes catchable at the microscale and nanoscale. In recent work, we obtained a considerable flexoelectric-like response by crumpling the dielectric embedded with charges, i.e., the electret, which significantly improved the flexoelectric effect at the macroscale. In this work, we further optimize the macroscopic performance of the flexoelectric response by applying gradient treatment to the electret films. Specifically, we analytically derive the electromechanical coupling of crumpled electret films with gradients of different thicknesses, charge densities, and Young's moduli as key design variables. It is shown that the gradient-oriented electret film can be tuned to nearly five times that of a uniform electret film. [ABSTRACT FROM AUTHOR]

Evaporation deposition of gold nanoparticles (AuNPs) on a glass surface textured by cellulose nanofibers (CNFs) provides an effective substrate for surface-enhanced Raman spectroscopy (SERS). The performance enhancement of such a SERS substrate hinges upon the quality and quantity of nanostructured surfaces, which are strongly correlated to the AuNP particle size. Unfortunately, the size effect of AuNPs on the Raman activity of CNF-textured SERS substrates remains unclear. Here, we investigate the Raman activity of CNF-textured SERS substrates constructed by evaporating sessile drops of AuNPs with diameters of 40 nm and 16 nm on CNF-textured surfaces, respectively. Both experimentation and computation analysis reveal that the use of 40 nm AuNPs exhibits more effective Raman activity and traps larger amounts of analyte molecules than 16 nm AuNPs. Moreover, the existence of the CNF-textured surface significantly enhances the Raman signals of analyte molecules in all regions of SERS substrates when compared with AuNPs deposited on the bare glass surface. These findings provide insights into the particle size selection for fabricating effective SERS substrates and advance applications of CNF-textured SERS substrates. [ABSTRACT FROM AUTHOR]

The fatigue of adhesive joints in offshore wind turbine blades is a critical and widespread challenge, necessitating an urgent focus on adhesive bond reliability. Given the constraints of full-scale testing, this research explores the fatigue endurance of carbon fiber–epoxy adhesive composites, integral to blade construction. Recognizing the fatigue characteristics’ sensitivity to environmental factors and joint dimensions, an innovative approach to fatigue modelling and evaluation is introduced. This method incorporates the influence of different environmental stresses and size effects. Specifically, a degradation coefficient and size impact factor (SIF) are introduced into the cyclic cohesive zone model, and a simulation-based analytic approach is proposed for analyzing adhesive fatigue. Furthermore, we introduce a reliability modelling procedure that integrates performance degradation theory to address the deteriorative characteristics inherent in adhesive fatigue. Subsequently, the specimens’ damage accumulation increased by 75% because of the stresses and escalated to 85% with adhesive joint size effects, causing carbon fiber Reinforced Polymer/epoxy adhesive joints to fail interfacially rather than in a mixed-mode manner. This study provides valuable insights for the safety analysis and assessment of adhesive joint performance in offshore wind turbine blades.

BACKGROUND: Nanotechnology has been widely applied in agricultural science. During the process of reducing metal toxicity and accumulation in rice, nanomaterials exhibit size effects. However, there is limited knowledge regarding these size effects. We aim to explore the impact of fertilizer with various sizes of ZnO nanoparticles (ZnO‐NPs) on rice growth and cadmium (Cd) accumulation and to elucidate the potential mechanism of Cd reduction in rice. Foliar applications of different concentrations (0.5 and 2 mmol L−1) and different sizes (30 and 300 nm ZnO‐NPs) of zinc (Zn) fertilizer (Zn(NO3)2) were performed to investigate the effects on rice growth, Cd accumulation and subcellular distribution, and the expression of Zn–Cd transport genes. RESULTS: The results suggested that all the foliar sprayings can significantly reduce the Cd concentrations in rice grains by 41–61% with the highest reduction in the application of ZnO‐NPs with large size and low concentration. This is related to the enhancement of Cd fixation in leaf cell walls and downregulation of Cd transport genes (OsZIP7, OsHMA2, OsHMA3) in stem nodes. Foliar ZnO‐NPs applications can increase the Zn concentration in grains by 9–21%. Foliar applications of Zn(NO3)2 and small‐sized ZnO‐NPs promoted plant growth and rice yield, while the application of large‐sized ZnO‐NPs significantly reduced rice growth and yield. CONCLUSION: The study suggests that the rice yield and Cd reduction are dependent on the size and concentration of foliar spraying and the use of large‐sized ZnO‐NPs is the most effective strategy when considering both yield and Cd reduction comprehensively. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The present paper investigates flaw strength distributions established using various flexural tests on batches of SiC bar test specimens, namely four-point bending as well as three-point bending tests with different span lengths. Flaw strength is provided by the elemental stress operating on the critical flaw at the fracture of a test specimen. Fracture-inducing flaws and their locations are identified using fractography. A single population of pores was found to dominate the fracture. The construction of diagrams of p-quantile vs. elemental strengths was aimed at assessing the Gaussian nature of flaw strengths. Then, empirical cumulative distributions of strengths were constructed using the normal distribution function. The Weibull distributions of strengths are then compared to the normal reference distributions. The parameters of the Weibull cumulative probability distributions are estimated using maximum likelihood and moment methods. The cumulative distributions of flexural strengths for the different bending tests are predicted from the flaw strength density function using the elemental strength model, and from the cumulative distribution of flexural strength using the Weibull function. Flaw strength distributions that include the weaker flaws that are potentially present in larger test pieces are extrapolated using the p-quantile diagrams. Implications are discussed regarding the pertinence of an intrinsically representative flaw strength distribution, considering failure predictions. Finally, the influence of the characteristics of fracture-inducing flaw populations expressed in terms of flaw strength interval, size, dispersion, heterogeneity, and reproducibility with volume change is examined.

Although various simplified models can capture size effects of composite laminated micro beam and plate by combining new modified couple stress theory, there is no benchmark to access the accuracy of predicting size effects in those models. Therefore this paper develops a quasi-3D model based on new modified couple stress as a benchmark for analyzing thermal size effects of composite laminated micro plate, and also proposes two simplified quasi-3D models with assumptions out of computational cost at the same time. By a classical example of simply-supported micro laminated square plate, several conclusions can be got from numerical results. For the present quasi-3D model under non-uniform temperature loading, (i): the model is capable to capture size effects of composite laminated micro plate, (ii): discovering a law to define the boundary size between micro and macro laminated plate, which is important for the engineering applications; For the simplified quasi-3D models under uniform temperature loading, (i): As the material length parameter l decreases, the accuracy of both of models is rising gradually, (ii): The first simplified quasi-3D model may substitute the present quasi-3D model to predict thermal size-dependent behaviors of composite laminated micro plate, whereas the second simplified quasi-3D model is suitable to laminated micro plate for which span-to-thickness ratio is no less than 14. [ABSTRACT FROM AUTHOR]

In this work, nonlocal strain gradient integral model is applied to investigate the free damping vibration analysis of functionally graded (FG) viscoelastic Timoshenko microbeam with immovable boundary conditions in thermal environment. The microbeam is assumed to be viscoelastic and modeled by Kelvin–Voigt model. The differential governing equations and corresponding boundary conditions are derived with the Hamilton's principle. Combining nonlocal strain gradient integral model and Kelvin–Voigt viscoelastic model, the integral constitutive equations of nonlocal stress with thermal effect are derived and then converted into differential form plus constitutive constraints. The size-dependent axial force due to thermal expansion is explicitly derived through the immovable boundary conditions. The bending deflection and moment, cross-sectional rotation as well as shear force are explicitly derived with Laplace transformation for linear thermo-elastic vibration. Taking into account the boundary conditions as well as constitutive constraints, one gets a nonlinear equation with complex coefficients, from which one can determine the complex characteristic frequency. A two-step numerical method is proposed to solve the elastic vibration frequency and damping ratio. The influence of length scale parameters, viscos coefficient, FG index, thermal effect, vibration order and ratio between beam length and thickness on the vibration frequencies and damping ratio is investigated numerically for FG viscoelastic Timoshenko microbeams under different immovable boundary conditions. [ABSTRACT FROM AUTHOR]

Copper with equiaxed grains (EG Cu), copper with columnar nanotwinned grains (C‐NT Cu), and copper with mixed equiaxed and columnar grains (MG Cu) are electroplated on pads and redistributed layers (RDLs) with different dimensions. When the diameters of pads increase from 40 to 105 μm, the flatness of pads decreases from 34.5% to 24.0%. The flatness gradually deteriorates from 16.5% to 34.4% with the increase of RDL width from 8 to 20 μm. In contrast, the flatness of C‐NT Cu and MG Cu fluctuates between 1% and 5%, showing a weak correlation on the dimension. In terms of microstructure, the EG Cu and MG Cu has a weak correlation with size change, and the grain orientation shows a randomness. However, the (111) texture component of C‐NT Cu differs greatly with different dimensions, especially in transition layer. The (111) texture component changes from 9.6% to 38.1% for ϕ 40–105 μm pad and from 14.3% to 18.9% for 8–20 μm‐wide RDL. The study reveals the significant size effect on the deposited profile and microstructure of electrodeposited copper materials, which should give insights of the materials design in advanced packaging technology. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is often used to create designs inspired by topology optimization and biological structures, yielding unique cross-sectional geometries spanning across scales. However, manufacturing defects intrinsic to AM can affect material properties, limiting the applicability of a uniform material model across diverse cross-sections. To examine this phenomenon, this paper explores the influence of specimen size and layer height on the compressive modulus of polycarbonate (PC) and thermoplastic polyurethane (TPU) specimens fabricated using fused filament fabrication (FFF). Micro-computed tomography imaging and compression testing were conducted on the printed samples. The results indicate that while variations in the modulus were statistically significant due to both layer height and size of the specimen in TPU, variations in PC were only statistically significant due to layer height. The highest elastic modulus was observed at a 0.2 mm layer height for both materials across different sizes. These findings offer valuable insights into design components for FFF, emphasizing the importance of considering mechanical property variations due to feature size, especially in TPU. Furthermore, locations with a higher probability of failure are recommended to be printed closer to the print bed, especially for TPU, because of the lower void volume fraction observed near the heated print bed. [ABSTRACT FROM AUTHOR]

The present paper investigates flaw strength distributions established using various flexural tests on batches of SiC bar test specimens, namely four-point bending as well as three-point bending tests with different span lengths. Flaw strength is provided by the elemental stress operating on the critical flaw at the fracture of a test specimen. Fracture-inducing flaws and their locations are identified using fractography. A single population of pores was found to dominate the fracture. The construction of diagrams of p-quantile vs. elemental strengths was aimed at assessing the Gaussian nature of flaw strengths. Then, empirical cumulative distributions of strengths were constructed using the normal distribution function. The Weibull distributions of strengths are then compared to the normal reference distributions. The parameters of the Weibull cumulative probability distributions are estimated using maximum likelihood and moment methods. The cumulative distributions of flexural strengths for the different bending tests are predicted from the flaw strength density function using the elemental strength model, and from the cumulative distribution of flexural strength using the Weibull function. Flaw strength distributions that include the weaker flaws that are potentially present in larger test pieces are extrapolated using the p-quantile diagrams. Implications are discussed regarding the pertinence of an intrinsically representative flaw strength distribution, considering failure predictions. Finally, the influence of the characteristics of fracture-inducing flaw populations expressed in terms of flaw strength interval, size, dispersion, heterogeneity, and reproducibility with volume change is examined. [ABSTRACT FROM AUTHOR]

Herein, we prepared Pd nanoparticle (NP) catalysts using XC-72 carbon supports through a tailored deposition–precipitation method. Our primary objective was to unravel the size effects of Pd NPs on hydrogenation of tetraacetyldibenzylhexaazaisowurtzitane (TADBIW), a pivotal intermediate for synthesis of high energy density materials hexanitrohexaazaisowurtzitane (CL-20). The controlled modulation of Pd NP size ranged from a mere 1.8 nm to 7.4 nm. Remarkably, our investigations into TADBIW hydrogenation unveiled a fascinating trend: the ultrasmall-sized Pd NPs with a diameter of 1.8 nm exhibited excellent yield and reaction rates. In stark contrast, their larger-sized counterparts demonstrated diminished catalytic activities. To disclose the size-dependent nature, various characterization techniques were employed, including XRD, TEM, XPS, CO and H2 pulse chemisorption. The comprehensive analysis revealed that the ultrasmall-sized Pd possessed more positively charged sites and exhibited higher dispersion. This unique configuration facilitated an accelerated adsorption of hydrogen and the electron-rich substrate TADBIW. Notably, this phenomenon led to a reduction in the activation energy through a thermodynamic effect, thereby enhancing overall catalytic performance. Our results strongly suggested that the ultrasmall-sized Pd NPs can exert a dominated influence on the physical and chemical states of the active sites, playing a key role in triggering the adsorption and activation of the substrate TADBIW. These findings not only deepen our understanding of the intricate connections between Pd NP size and catalytic activity but also open new avenues for advancing the design and optimization of catalysts in the hydrodebenzylation methodologies and synthesis of related compounds. [ABSTRACT FROM AUTHOR]

Context: Mixed-metal clusters have long been studied because of their peculiar properties and how they change with cluster size, composition, and charge state and their potential roles in catalysis. The characterization of these clusters is therefore a very important issue. One of the main experimental tools for characterizing their electronic structure is photoelectron spectroscopy. Theoretical computation completes the task by fully determining the structural properties and matching the theoretical predictions to the measured spectra. We present density functional theory computations of the structural, magnetic, and electronic properties of negatively charged mixed AlnNi- clusters with up to 13 Al atoms. The lowest energy structures of the anionic clusters with up to 7 atoms are also found to be low-energy isomers of the neutral counterparts found in the literature. The 13-atom cluster is found to be a quartet and a perfect icosahedron. The predicted photoelectron spectra are also presented and can be used to interpret future experimental data. We also presented indicators that can be used to determine the potential of these systems for single-atom catalysis. These indicators point to smaller clusters to be more reactive as the gap between the Fermi energy and the center of the d-band increases with cluster size and that Ni occupies an internal site for n = 11–13. We speculate that reactivity can be enhanced if one adds an additional Ni atom. Methods: The DFT calculations were performed using the Becke exchange and Perdew-Wang/91 correlation functionals (BPW91), a DFT-optimized all-electron basis set for the aluminum atom, and the Stuttgart small core pseudopotential for the Ni atom. All of the computations used the Gaussian 03 software. [ABSTRACT FROM AUTHOR]

Based on the hyperbolic tangent parabola mixed shear deformation theory, the paper studied the sound radiation and the sound insulation of the functionally graded (FG) sandwich microplates under thermal-electric effects. The sandwich plate is composed of piezoelectric skin layers and FGM core layer. By using Hamilton's principle, a size-dependent model considering the thermal-piezoelectric effects are established. The acoustic response and sound insulation are calculated with Rayleigh integral and solid-fluid coupling conditions. The accuracy of the presented method is verified by the numerical simulations. Then the effects of various parameters on the vibro-acoustic characteristics are analyzed and discussed. Numerical results show that the temperature variations, the length scale parameter to thickness ratio and the gradient index have great impacts on the FG sandwich microplates. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on ultra-high-performance concrete (UHPC) beams without stirrups, where the test data of 487 beams were collected, and an experimental database was established. Four distinct shear strength calculation models for UHPC beams were examined in the study. These models were created from national specification guides. The results indicate that while the code equation is useful for predicting UHPC beam shear capacity, it consistently underestimates actual values, with a mean experimental-to-calculated ratio above 1.5. The database was also used to study the impacts of the compressive strength of UHPC, the shear span-to-depth ratio, the fiber volume fraction, and the reinforcement ratio on the shear strength of UHPC beams. The findings showed that the shear span-to-depth ratio significantly affected the shear load-bearing capacity of UHPC beams. The increase in the compressive strength of UHPC, fiber volume fraction, and reinforcement ratio positively affected the shear strength of UHPC beams to varying degrees. Additionally, there were size effects for beams with a shear span-to-depth ratio of less than 1.5 and an effective depth of more than 300. In addition, coefficients accounting for fiber influence and the shear span-to-depth ratio were incorporated to develop an enhanced formula for UHPC beams. The empirical data from the database tests revealed that the average ratio of the beams' experimental shear capacity to the values predicted by the modified equation is 1.3, with a standard deviation of 0.74. These results suggest that the refined equation offers improved calculation precision and broader applicability. Eventually, a summary of the issues pertaining to the shear performance of UHPC beams and the key future research directions is provided to facilitate a clearer comprehension and awareness of emerging concepts for scholars within the discipline. [ABSTRACT FROM AUTHOR]

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Abstract The dimensionality of dynamic interfaces—domain walls (DWs) —is greatly influenced by symmetry and physical dimensions, irrespective of the microscopic details of the system. To address this fundamental question for the ferroelectric model system, the DW scaling criticality and dimensionality is investigated in ultrathin films of varied ferroelectric materials, compositions, and electrode–ferroelectric interfaces, grown on nominally flat and vicinal substrates. In spite of significant variations among ferroelectric systems, the observed prevalence of 1D DWs is consistent with a random bond disorder, elucidated through a scenario of 2D nucleation and growth‐driven DW creep. These findings highlight the thickness size‐dominated universal behavior of ferroelectric DWs, uncovering fascinating prospects for dimensionally engineered DW‐based nanoelectronics.

Despite extensive studies on size effects in ferroelectrics, how structures and properties evolve in antiferroelectrics with reduced dimensions still remains elusive. Given the enormous potential of utilizing antiferroelectrics for high-energy-density storage applications, understanding their size effects will provide key information for optimizing device performances at small scales. Here, the fundamental intrinsic size dependence of antiferroelectricity in lead-free NaNbO3 membranes is investigated. Via a wide range of experimental and theoretical approaches, an intriguing antiferroelectric-to-ferroelectric transition upon reducing membrane thickness is probed. This size effect leads to a ferroelectric single-phase below 40 nm, as well as a mixed-phase state with ferroelectric and antiferroelectric orders coexisting above this critical thickness. Furthermore, it is shown that the antiferroelectric and ferroelectric orders are electrically switchable. First-principle calculations further reveal that the observed transition is driven by the structural distortion arising from the membrane surface. This work provides direct experimental evidence for intrinsic size-driven scaling in antiferroelectrics and demonstrates enormous potential of utilizing size effects to drive emergent properties in environmentally benign lead-free oxides with the membrane platform.

Ion beam implantations are widely performed to understand the effects of irradiation-induced displacement damage on nuclear structural materials. However, the volume of material that can be investigated is often limited by the maximum energies of accelerator facilitates, leading to a limitation in the thickness of samples whose mechanical properties can be evaluated. The Lawrence Berkeley National Laboratory's 88-Inch Cyclotron offers a wide range of ions and energies, allowing for material ion implantations at larger scales than typical. Four HT-9 SS-J-geometry tensile specimens were polished and then irradiated with deuterons at the 88-Inch Cyclotron to doses of approximately 0.2 dpa prior to small scale tensile testing. The results from this study show irradiation hardening characterized by the tensile test results and black dot irradiation defects. Additionally, a comprehensive look at low temperature irradiations of high-Cr F/M steels is presented and our results show agreement with the available data.

A hybrid planar micro-lattice made of functionally graded materials is proposed where the active and passive constituents are constructed by functionally graded beams with and without partially distributed piezoelectric attachments respectively. The analytical model for predicting complex band structure is presented via the spectral element method in combination with the modified couple stress theory and power law, whose accuracy is validated by the finite element method. By adjusting size dependence, feedback control gain, material gradient and arrangement of piezo-patches, controllable wave propagation and attenuation is achieved, which further advances the implementation of optimizations to obtain ultra-wide low frequency stop bands. [ABSTRACT FROM AUTHOR]

It is now well established that, upon decreasing system sizes down to a few μ m or below, the nature of plasticity of metallic materials is changing. Two important features of this small-sizes plasticity are two size effects, which can be summed up as "smaller is stronger" and "smaller is wilder", this last observation meaning that the jerkiness of plastic deformation becomes prominent at small enough system sizes. In FCC and HCP materials, this is now rather well understood within the framework of obstacle-controlled plasticity, from the key role of a scaling ratio between the system size L and an internal scale l mainly dictated by dislocation patterning in pure materials, or by the nature of extrinsic disorder in alloys. The situation is more complex in BCC materials, for which screw dislocation motion becomes lattice-controlled, i.e. is thermally activated, below a transition temperature T a . Therefore, in small-sized BCC systems, temperature, size and strain-rate effects combine to give rise to a complex landscape. We show, from an analysis of the literature as well as micropillar compression tests on Molybdenum performed with different sample sizes, under different temperatures and different applied strain-rates, that (i) near or above T a , the plasticity of pure BCC metals is athermal and obstacle-controlled, much like at bulk scales, therefore mimicking that of pure FCC metals; (ii) below T a and for sample sizes larger than ∼ 1 μ m, BCC plasticity becomes lattice-controlled, this damping dislocation avalanches and thus reducing wildness; but (iii) for very small systems, still below T a , the role of screw dislocations on plasticity vanishes, i.e. is no more lattice-controlled, opening again the door for wild plastic fluctuations and jerkiness. [ABSTRACT FROM AUTHOR]

Demand for micro-deep-drawn complex-shaped parts in biomedical, chemical analysis and microsystem technologies has been growing. Micro-deep drawing is a micro-plastic forming used to produce micro-parts from different materials. Researchers have worked upon several aspects of micro-deep drawing (MDD), namely the scaling effects, handling of micro-parts and process intermittency. The present work reviews some of these experimental and numerical studies on the MDD considering the size effects, forming limit diagram, parametric effect, lubrication and coating on punch and die surfaces. The topology modification of the deep drawing tool surface using macro/microstructured coated tool shows substantial potential for the lubricant-free micro-deep drawing. Further, micro-structuring of the blank via laser has emerged as another approach in the MDD process to reduce the effective contact area between tool and sheet and, hence, the friction forces. Finally, challenges and scope for further research in MDD are listed to implement these processes commercially. [ABSTRACT FROM AUTHOR]

The microalloyed high-strength aviation alloy of the Al-Si-Cu system obtained using additional pressure on the melt during crystallization is studied in the work. The technology and design features of laminar filling of the mould are developed in order to minimize the formation of technological casting defects. The peculiarities of the structure and crystallization conditions of the AK9M2 alloy are studied. The level of physical-mechanical properties of obtained alloy and its fracture behaviour are determined. Mechanisms of heat transfer are analysed and determined, which allow the promising use of obtained alloys as a material for heat-exchange applications. [ABSTRACT FROM AUTHOR]

Bifunctional metal/zeolite materials are some of the most suitable catalysts for the direct hydroalkylation of benzene to cyclohexylbenzene. The overall catalytic performance of this reaction is strongly influenced by the hydrogenation, which is dependent on the metal sizes. Thus, systematically investigating the metal size effects in the hydroalkylation of benzene is essential. In this work, we successfully synthesized Ru and Pd nanoparticles on Sinopec Composition Materials No.1 zeolite with various metal sizes. We demonstrated the size-dependent catalytic activity of zeolite-supported Ru and Pd catalysts in the hydroalkylation of benzene, which can be attributed to the size-induced hydrogen spillover capability differences. Our work presents new insights into the hydroalkylation reaction and may open up a new avenue for the smart design of advanced metal/zeolite bi-functional catalysts. [ABSTRACT FROM AUTHOR]

The use of supported Co-based catalysts is widespread in various catalytic reactions due to their unique structures. The structural sensitivity of these catalysts is closely linked to their particle size and crystal form. Consequently, comprehending the structure-activity relationship requires the development of well-defined Co-based catalysts. Herein, we employed a colloidal wet chemical process and a heterogeneous nucleation method to prepare well-defined Co-based catalysts supported by inert carbon nanospheres. The nanospheres' surface possesses abundant functional groups that efficiently capture metal complexes and facilitate the nucleation and growth of CoO nanoparticles. By adjusting the Co source concentration, solvent molar ratio, and nucleation growth kinetics, we successfully prepared CoO/carbon sphere (CS) catalysts with different particle sizes and crystal forms. The influence of metallic face-centered cubic (fcc)-Co0 particle size in the range of 6.6–17.6 nm on the performance of Fischer-Tropsch synthesis (FTS) using well-defined CoO/CS catalysts has been investigated. The result demonstrated that the turnover frequency (TOF) remained constant for CoO/CS catalysts with metallic fcc-Co0 particle size larger than 7.7 nm. However, both the selectivity and the activity changed for CoO/CS catalysts with smaller particles (< 7.7 nm). Significantly, when metallic fcc-Co0 particle size was reduced from 17.6 to 7.7 nm, the cobalt time yield increased to 6.7 µmolCO·gCo−1·s−1, indicating improved catalytic activity. At the same time, the CH4 selectivity decreased to 4.9%, suggesting a higher preference for hydrocarbon production. These findings demonstrate the importance of particle size in Co catalyzed Fischer-Tropsch synthesis. The use of well-defined CoO/CS catalysts offers valuable insights into the structure-activity relationship, leading to a better understanding of Co catalyzed Fischer-Tropsch synthesis. [ABSTRACT FROM AUTHOR]

Numerical modeling of concrete fractures is of prime importance in the durability assessment of civil engineering structures. The phase field model has been demonstrated as a promising framework to simulate crack propagation in brittle material while using the many existing techniques. In this paper, we discuss choosing the most appropriate phase field model for describing the fracture behavior of concrete. More specifically, we present a detailed analysis of the existing models, which have been created by combining different spectral decompositions and crack density functions. The numerical simulation predictions are confronted with the experimental observation of a benchmark problem from the literature. The obtained results showed that the extensive/ compressive decomposition and the quadratic crack density function are the most suitable models to study concrete cracking behavior. The investigation's size effects demonstrated heterogeneities played an important role in concrete's post-cracking behavior and softening branches, especially for the small concrete structure. [ABSTRACT FROM AUTHOR]

The discovery of deepwater oil and gas sources has altered the scenario of world production of oil products, attracting even more attention to nickel superalloys. However, this class of materials can be used in several applications. Furthermore, nickel superalloys are highly dependent on their processing history, and the manner in which superalloys react to machining can directly affect the finished product. This work aims to evaluate the surface integrity of two different materials after cryogenic side-milling in conditions that stimulate severe plastic deformation (SPD) and high heat generation. The results show that the material response to machining depends strongly on the pre-processing route instead of most assumptions. While cryogenic cooling led to significant sub-surface hardness and microstructural changes in wrought Inconel 625 alloy, such changes were not observed for clad Inconel 625. Therefore, in order to achieve significant surface integrity changes, process parameters need to be selected and optimized accordingly. Also, the findings indicate that some new factors established significant affect/change surface integrity: (a) SPD through a high rβ/h ratio; (b) the specific pre-processing thermomechanical history of the workpiece material; and (c) and cryogenic cooling, by changing material properties, reducing temperature and altering cutting phenomena and chip formation. [ABSTRACT FROM AUTHOR]

Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) stands out among lead‐free ferroelectric oxides under consideration to replace state‐of‐the‐art high‐sensitivity piezoelectric Pb(Zr,Ti)O3, for a range of energy conversion ceramic technologies. However, the best performances have been reported for very coarse‐grained materials, and attempts to refine microstructure below 10 µm grain size consistently result in significant property degradation. Here a comprehensive study of the grain size effects on the properties of BCZT across the micron scale is reported, down to the verge of the submicron one. Results show a distinctive early evolution of properties for grain sizes between 1 and 5 µm. For the larger sizes in this range, an opposite effect is found for the piezoelectric charge coefficient and electric field‐induced strain with respect to the very coarse‐grained material, while very good overall performance is maintained. For the lower sizes, relaxor features appear, yet materials can still be poled indicating their ferroelectric nature. This strongly resembles size effects in the Pb(Mg1/3Nb2/3)O3‐PbTiO3 system, driven by the slowing down of the relaxor to ferroelectric transition with size reduction, though kinetics seem to slow down across much larger grain sizes for BCZT. Concomitant changes in the polymorphic phase coexistence are described and discussed by synchrotron X‐ray diffraction. [ABSTRACT FROM AUTHOR]

We derive two different effective models from a heterogeneous Cosserat continuum taking into account the Cosserat intrinsic length of the constituents. We pass to the limit using homogenization via periodic unfolding and in doing so we provide rigorous proof to the results introduced by Forest, Pradel, and Sab (Int. J. Solids Struct. 38 (26-27): 4585-4608 '01). Depending on how different characteristic lengths of the domain scale with respect to the Cosserat intrinsic length, we obtain either an effective classical Cauchy continuum or an effective Cosserat continuum. Moreover, we provide some corrector type results for each case. [ABSTRACT FROM AUTHOR]

The corrugated sheet is a crucial component of the metal honeycomb structure. This study investigates the size effects on the deformation behavior of ultra-thin-walled corrugated sheets in the roll bending process using experimental and simulation methods. A precision roll bending device was developed, which incorporated a specifically designed eccentric fine-tuning module and a pneumatic module to prevent the distortion and insufficient deformation of the ultra-thin-walled corrugated sheets. The experimental results showed that micro-scratches and orange peel phenomenon appeared in the bending region of ultra-thin-walled corrugated sheets due to the lack of grain deformation coordination. Decreasing the ratio of foil thickness to grain diameter (t/d value) resulted in a slight increase in edge lengths, but a sharp decrease in the thickness of the bending region of ultra-thin-walled corrugated sheets. For the ultra-thin-walled corrugated sheet with a t/d value of 1.2, its thickness was reduced by 14%, leading to a high risk of rupture. Consequently, a finite element model of the roll bending process was established with consideration of the heterogeneity of grain shape and grain orientation. The simulation results indicate that the prediction error of the model for the springback angle was less than 15%. The random distribution of elastic deformation and plastic penetration zones is responsible for the great scatter of the springback angle of ultra-thin-walled corrugated sheets. This research provides a theoretical foundation for the precision manufacturing of ultra-thin-walled corrugated sheets. [ABSTRACT FROM AUTHOR]

Сучасні технології електроніки і сенсорної техніки дозволяють отримувати плівкові матеріали нанометрової товщини із унікальними властивостями, які не є типовими для масивного стану. Експериментально встановлено, що перехід від масивного до плівкового матеріалу призводить до змін його фізичних властивостей. Основні причини цього пов’язані: з різною структурою матеріалів; розмірними ефектами, які виникають у результаті обмеження середньої довжини вільного пробігу носіїв електричного струму зовнішніми поверхнями плівки або геометричними розмірами кристалітів; зміною частотних і енергетичних характеристик атомів кристалічної решітки під дією температурного фактору. На основі температурних залежностей питомого опору одношарових металевих плівок благородних металів (Pd, Pt і Ag) проаналізовані особливості високотемпературної електрон-фононної взаємодії. Нами установлено, що кутовий коефiцiєнт лiнiйної дiлянки температурних залежностей питомого опору одношарових плiвок зростає при зменшеннi їх товщини. При зменшенні товщини плівки середня енергія фонона збільшується, що призводить до підвищення ефективності електрон-фононного розсіювання і, як наслідок цього, – зростання питомого опору. [ABSTRACT FROM AUTHOR]

The utilization of nanoscale catalysts represents a valuable and promising strategy for augmenting catalytic performance while mitigating the reliance on expensive noble metals. Nevertheless, a significant knowledge gap persists regarding the intricate interplay between catalyst size, physical properties, and catalytic behavior in the context of the oxygen reduction reaction. In this study, the synthesis of precisely controlled palladium catalysts is presented, spanning a wide range from individual atoms to metal clusters and nanoparticles, followed by a comprehensive evaluation of their performance in acidic conditions. The results show a significant increase in H2O2 selectivity of up to 96% with decreasing catalyst size and strategic approaches are identified to eliminate unselective sites, facilitating the attainment of active and selective catalysts. The enhanced selectivity of the catalysts highlights the potential of single atom catalytic sites and can be adapted to improve the performance of various catalytic processes. [ABSTRACT FROM AUTHOR]

A previously proposed strain gradient plasticity theory is extended to incorporate a non-quadratic power law function of the plastic strain gradient in the free energy expression with an exponent of N + 1. The values of N are taken to vary from N = 1 to N = 0. A simple shear problem of a metal layer between rigid boundaries is analyzed. Two stages of plastic deformation are considered. In stage I, the plastic strain is taken to be zero at the boundaries. Stage I ends when a specified magnitude of the plastic strain gradient is attained at the boundaries. In stage II, the magnitude of the plastic strain gradient at the boundaries is fixed at the specified value. With N = 0, a critical plastic strain gradient cannot be specified at the boundaries because the plastic strain gradient is infinite at the boundaries. The theory with N = 0 predicts a constant plateau stress immediately after initial yield, and the dependence of the plateau stress on the layer thickness can fit experimentally observed plateau stress values. However, with N = 0, a stress gap occurs between the initial yield stress and the plateau stress. The theory with 0 < N = 1 and with stage II also can reproduce the experimentally observed dependence of the plateau stress on the layer thickness for any value of N in that range, with an appropriate value of critical plastic strain gradient at the boundaries. The solution for 0 < N = 1 includes that for N = 0 as a limiting case. [ABSTRACT FROM AUTHOR]

An existing hydroelectric facility affected by alkali–aggregate reaction (AAR) is considered in this study through numerical and experimental investigations. A new developed phenomenological hygro–chemo–mechanical approach for AAR is presented and is shown to be practical and effective in damage assessing of large-scale hydraulic concrete structures. Experimental investigations were conducted to characterize the AAR kinetics of mass concrete mixture with very large aggregates, used in the construction of the facility. By combining experimental, numerical, and monitoring investigations, it was possible to assess size effects related to the free AAR expansion of mass concrete. Numerical simulations allowed to obtain a damage pattern similar to the cracking profile of the existing facility, to provide mechanical interpretation of the jumps observed in the instrumentation data, and most importantly, to predict the remaining time before reaching the asymptotic expansion of the facility: a very important result for owners of hydroelectric facilities affected by AAR. [ABSTRACT FROM AUTHOR]

Size plays an important role on the deformation mechanism of nanopillars. With decreasing size, many FCC nanopillars exhibit dislocation starvation which is responsible for their high strength. However, many details about the dislocation starvation like how often it occurs, and how much is its contribution to the total plastic strain, are still elusive. Similarly, the size below which the dislocation starvation occurs is not clearly established. In this context, atomistic simulations have been performed on the compression of <110> Cu nanopillars with size (d) ranging from 5 to 21.5 nm. Molecular dynamics (MD) simulation results indicate that the nanopillars deform by the slip of extended dislocations and exhibit dislocation starvation mainly at small sizes (<20 nm). The frequency of the occurrence of dislocation starvation is highest in small-sized nanowires and it decreases with increasing size. Above the size of 20 nm, no dislocation starvation has been observed. Furthermore, we define the dislocation starvation strain and based on this, it has been shown that the contribution of the dislocation starvation to the total plastic strain decreases from 70% in small-sized nanopillars to below 5% in large-sized pillars. The present results suggest that dislocation starvation is a dominant phenomenon in small-sized nanopillars. [ABSTRACT FROM AUTHOR]

By the example of electrodeposition of Co–W alloys, this work shows that observed peculiarities of induced codeposition, including the macroscopic size effect in the composition and properties of deposited layers and their nanocrystallinity, are a consequence of the fact that the deposition-inducing species (a complex of the deposition-inducing metal) has the form of a high-molecular-weight polymer. Under the conditions of (relatively) high current loading on a plating electrolyte (high volume current density), this results in involvement of water molecules in the electrochemical process, formation of oxy-hydroxide layers, hydrogenation, an increase in the alloy tungsten content as a result of the side reaction of hydrogen evolution, alkalization of near-electrode region, and polymerization of the deposition-inducing metal species. Because of the presence of macroscopic size effect (i.e., the dependences of composition and properties of deposited coatings on the electrodeposition surface area), industrial scaling up of this electrodeposition technology will require maintaining the current loading on a plating bath at a constant level, along with other parameters traditional for electrochemical materials science. [ABSTRACT FROM AUTHOR]

The behavior of copper ion-exchange composites with metal particles of various sizes and contents in the electroreduction of oxygen dissolved in water have been studied. The primary size effect is significant for samples with low metal capacity: the smaller the metal particle size, the higher the process rate. At the same time, for samples with high metal capacity, the process occurs at approximately the same rate on copper particles obtained using different reducing agents due to the comparable size. A secondary size effect is observed due to the collective interaction of metal particles. The size effect was taken into account along with the effect of the content of metal particles using the proposed nanosized complex, which represents the ratio of capacity and size. At the level of electronic conductivity percolation, the nanosized complex reaches the limiting value corresponding to the highest degree of development of the reaction surface, which makes it possible to increase the current to the maximum current capacity. The reduction of oxygen occurs along several routes: electroreduction on copper particles, mainly on the surface of nanocomposite grains; and autocatalytic chemical reaction with electroregenerated metal nanoparticles in the nanocomposite grains. The electroreduction of oxygen generally reaches an intense steady-state mode. [ABSTRACT FROM AUTHOR]

This paper presents the derivation of the homogenized equations that describe the macroscopic mechanical response of elastomers filled with liquid inclusions in the setting of small quasistatic deformations. The derivation is carried out for materials with periodic microstructure by means of a two-scale asymptotic analysis. The focus is on the non-dissipative case when the elastomer is an elastic solid, the liquid making up the inclusions is an elastic fluid, the interfaces separating the solid elastomer from the liquid inclusions are elastic interfaces featuring an initial surface tension, and the inclusions are initially n -spherical (n = 2 , 3 ) in shape. Remarkably, in spite of the presence of local residual stresses within the inclusions due to an initial surface tension at the interfaces, the macroscopic response of such filled elastomers turns out to be that of a linear elastic solid that is free of residual stresses and hence one that is simply characterized by an effective modulus of elasticity L ‾ . What is more, in spite of the fact that the local moduli of elasticity in the bulk and the interfaces do not possess minor symmetries (due to the presence of residual stresses and the initial surface tension at the interfaces), the resulting effective modulus of elasticity L ‾ does possess the standard minor symmetries of a conventional linear elastic solid, that is, L ‾ i j k l = L ‾ j i k l = L ‾ i j l k . As an illustrative application, numerical results are worked out and analyzed for the effective modulus of elasticity of isotropic suspensions of incompressible liquid 2-spherical inclusions of monodisperse size embedded in an isotropic incompressible elastomer. [ABSTRACT FROM AUTHOR]

Size effects, influencing a material's strength, elongation, fatigue limit, and longevity, depend on the operative and dominant deformation and failure mechanisms. This study explores the size effects in additive manufactured (AM) GRCop-42 (Cu-4at%Cr-2at%Nb) thin wall structures fabricated via laser-powder bed fusion (L-PBF) and their impact on fatigue life. The influence of internal defects and surface topography on the fatigue life of specimens in both as-built and hot isostatic pressed (HIP) conditions across different thicknesses is investigated. Where micro-computed tomography (μCT) was used to quantify the internal porosity of as-built, pristine HIP'd, and fatigued HIP'd specimens, and laser microscopy was employed to quantify the surface topography of specimens prior to fatigue. Additionally, quasi-static tests were used to establish baseline mechanical properties (i.e. yield strength (YS), ultimate tensile strength (UTS), and elongation) to frame fatigue testing conditions. Results indicate a significant enhancement in fatigue life for HIP'd specimens for both thicknesses, with internal defects depicting a greater impact than surface topography. Furthermore, fractographic analysis suggests that thicker specimens exhibit higher resistance to crack propagation during fatigue testing in the absence of substantial porosity. Thus, the size effects observed on the fatigue life of L-PBF GRCop-42 appears to be dominated by internal defects.

Abstract Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) stands out among lead‐free ferroelectric oxides under consideration to replace state‐of‐the‐art high‐sensitivity piezoelectric Pb(Zr,Ti)O3, for a range of energy conversion ceramic technologies. However, the best performances have been reported for very coarse‐grained materials, and attempts to refine microstructure below 10 µm grain size consistently result in significant property degradation. Here a comprehensive study of the grain size effects on the properties of BCZT across the micron scale is reported, down to the verge of the submicron one. Results show a distinctive early evolution of properties for grain sizes between 1 and 5 µm. For the larger sizes in this range, an opposite effect is found for the piezoelectric charge coefficient and electric field‐induced strain with respect to the very coarse‐grained material, while very good overall performance is maintained. For the lower sizes, relaxor features appear, yet materials can still be poled indicating their ferroelectric nature. This strongly resembles size effects in the Pb(Mg1/3Nb2/3)O3‐PbTiO3 system, driven by the slowing down of the relaxor to ferroelectric transition with size reduction, though kinetics seem to slow down across much larger grain sizes for BCZT. Concomitant changes in the polymorphic phase coexistence are described and discussed by synchrotron X‐ray diffraction.

Dams fragment stream habitats and fishways around dams typically serve few species that are strong swimmers or jumpers. We tested a prototype wetted ramp designed to allow upstream passage of small-bodied fishes while blocking upstream movement of invasive sea lampreys in the Laurentian Great Lakes. We tested short, smooth ramps with 5–10 mm water depth in various combinations of ramp angle, water flow, and swim channel width with the aim to selectively block adult migrating sea lampreys (Petromyzon marinus) while passing sub-adult white suckers (Catostomus commersonii) and creek chubs (Semotilus atromaculatus). Sea lampreys easily passed a 0.75 ramp at a 5° angle, but very few individuals passed a similar ramp at a 10° angle, and none passed a longer ramp at a 5° angle. Limiting the amplitude of tailbeats in a narrow channel did not hamper lampreys or the other species. Greater water flow, and thereby greater immersion depth on the ramp, fostered passage for all species. Smaller-bodied individuals of creek chubs and white suckers performed best on the ramp. We showed that wetted ramps could be incorporated into fishways at low-head dams to aid the passage of smaller-bodied fishes while also blocking the spawning migration of adult sea lampreys.

Additive manufacturing (AM) is often used to create designs inspired by topology optimization and biological structures, yielding unique cross-sectional geometries spanning across scales. However, manufacturing defects intrinsic to AM can affect material properties, limiting the applicability of a uniform material model across diverse cross-sections. To examine this phenomenon, this paper explores the influence of specimen size and layer height on the compressive modulus of polycarbonate (PC) and thermoplastic polyurethane (TPU) specimens fabricated using fused filament fabrication (FFF). Micro-computed tomography imaging and compression testing were conducted on the printed samples. The results indicate that while variations in the modulus were statistically significant due to both layer height and size of the specimen in TPU, variations in PC were only statistically significant due to layer height. The highest elastic modulus was observed at a 0.2 mm layer height for both materials across different sizes. These findings offer valuable insights into design components for FFF, emphasizing the importance of considering mechanical property variations due to feature size, especially in TPU. Furthermore, locations with a higher probability of failure are recommended to be printed closer to the print bed, especially for TPU, because of the lower void volume fraction observed near the heated print bed.