Impact Of Grain Size Research Articles

Effect of grain size on mechanical properties and aging of yttria-stabilized tetragonal zirconia polycrystal fabricated by stereolithography-based additive manufacturing

The objective of this investigation was to comprehensively assess the impact of grain size on the mechanical properties and low-temperature degradation (LTD) of yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) fabricated by stereolithography-based additive manufacturing at the submicron scale. Four 3Y-TZP ceramics with high relative density (>98%), ranging in grain size from 0.2 μm to 1 μm, were successfully prepared and validated for studying mechanical properties (including Vickers hardness, fracture toughness, and flexural strength) as well as LTD progression. This study elucidates the mechanical behavior of zirconia ceramics at the submicron scale, focusing on fracture micromechanisms and the grain size dependence of transformation toughening. Additionally, it examines the influence of grain size on the hydrothermal aging behavior of zirconia ceramics at the submicron scale using Raman spectroscopy.

Impact of grain size on the performance of WSe2 FETs revealed by first-principles calculations

We theoretically investigate the grain size dependence of the mobility of WSe2 FETs, and the experimental results which have been recently reported. A larger grain size (LG) WSe2 has been modeled by a single monolayer WSe2 of infinite length. We model a smaller grain size (SG) WSe2 as a partial monolayer of WSe2 with a zigzag edge WSe2 nanoribbon. Our results show that the step edges of the partial monolayer WSe2 function as electron traps. Moreover, the effective mass of SG WSe2 appears to be much larger than that of LG WSe2 because of hybridization with gap states originating from step edges at the conduction band minimum. These results coincide with recent experiments that show that the on-currents of the SG WSe2 are much lower than those of the LG WSe2. Hence, our calculated results indicate that LG fabrication is essential for advanced large-scale integration (LSI) using WSe2 FETs.

Revealing the anisotropic response of grain structures in additive manufactured Al-Mn-Sc alloys: Modeling based on experiments

The anisotropy of yield strength of additive manufactured (AM) Al-Mn-Sc alloy is attributed to the diverse distribution characteristics of grain size, aspect ratio and orientation. This work focus on controlling the yield strength and anisotropy of AM aluminum through microstructure design. In this work, microstructures information of laser powder-bed fusion (LPBF) processed Al-Mn-Sc alloys were obtained by electron back scatter diffraction (EBSD) analysis. The impact of grain size, aspect ratio and orientation on strength and anisotropy are quantitatively researched through modeling. Base on quantitative effect of orientation on strength and anisotropy, all microstructure partition schemes are calculated by MATLAB. Microstructure partition schemes of alloy with low anisotropy and high yield strength were predicted and simulation was enforced to certify the credibility of predication. Local stress in grain and orientation variation during deforming were obtained by simulation. It is concluded that the impact of orientation is more obvious than grain size and aspect ratio. Compared with strength and anisotropy obtained by simulation, the prediction of calculation shows fine precision. The impact of microstructures on mechanical properties and the reliability of modeling were verified.

Design and development of a stand-off Raman brassboard (SDU-RRS) for the spectroscopic study of planetary materials

Raman spectroscopy has emerged as a crucial mineral analysis technique in planetary surface exploration missions. Nonetheless, the inherently low Raman scattering efficiency of planetary silicate materials makes it challenging to extract enough Raman information. Theoretical and experimental studies of the remote Raman scattering properties of planetary materials are also urgent requirements for future lunar and planetary explorations. Here, Shandong University Remote Raman Spectrometer (SDU-RRS) was developed to demonstrate the feasibility of lunar remote Raman technology and conduct preliminary research on remote Raman scattering properties. SDU-RRS utilizes a pulsed 532 nm laser, a non-focal Cassegrain telescope, a volume phase holographic grating, an intensified charge-coupled device, and the time-gating technique to detect weak-signal silicate minerals. The spectral resolution obtained with atomic emission lamps was <4.91 cm−1, and the wavelength accuracy was <1 cm−1, across the spectral range of 241–2430 cm−1. SDU-RRS can detect natural augite within a feldspar-olivine-augite matrix at a concentration of 20 % at ∼1 m under ambient lighting conditions. A series of experiments were conducted to evaluate the influence of measurement conditions and physical matrix effects on acquired Raman signals, either qualitatively or quantitatively, on geological materials. The study indicates that the transmission of Raman-scattered light conforms to Lambert’s cosine law, and a linear correlation exists between Raman intensity and laser power. The study also evaluated the impact of grain size, surface roughness, porosity, and shadow-hiding effects. Reducing grain size decreases Raman intensity and broadens Raman spectra. These characteristics are essential for achieving definitive mineralogical information from granular materials by remote Raman spectroscopy in lunar and planetary explorations.

Modeling the Impact of Grain Size on Corrosion Behavior of Ni-Based Alloys in Molten Chloride Salt via Cellular Automata

Modeling the Impact of Grain Size on Corrosion Behavior of Ni-Based Alloys in Molten Chloride Salt via Cellular Automata

On the fatigue crack growth behavior of nanocrystalline CrMnFeCoNi

The fatigue crack growth (FCG) behavior of the equimolar CrMnFeCoNi Cantor-alloy in the nanocrystalline grain size regime has been explored with special focus on the influence of specimen orientation and the effect of additional heat-treatments. For the synthesis severe plastic deformation using high-pressure torsion (HPT) was used. The results were critically discussed regarding the impact of grain size on the FCG-behavior and compared to a conventional 316L stainless steel in the nanocrystalline state: The reduction of grain size in the Cantor alloy from the micrometer to the nanometer regime invokes crack growth rates being about one order of magnitude higher paired with significantly lower threshold values. Furthermore, the sensitivity of thresholds and crack growth rates in the Paris regime on the applied load ratio in the NC material state is also profoundly reduced. This can be explained based on a diminishing contribution of crack closure effects, especially roughness induced closure. Even though the chemical composition differs distinctively, the crack growth rates and fatigue threshold values of the nanocrystalline Cantor alloy and the stainless steel are comparable with the latter being slightly lower for the CrMnFeCoNi alloy. Moreover, the extent of anisotropy is more pronounced than for 316L. Heat-treatment leading in the NC-Cantor alloy to an increasing hardness, has also an effect on the FCG-rate and depends on the specimen orientation. In addition, an unusual self-annealing behavior affecting the FCG behavior of the Cantor alloy was found.

Crystallite Size Effect on Photoluminescence of Combustion-Derived Gd2O3 Nanoparticles

Rare earth oxides are considered materials that are commonly used in high performance luminescent devices, magnets, catalysts and various other practical applications such, as electronics, magnetism, nuclear technology, optics and catalysis. Using [Formula: see text] nanoparticles synthesised by combustion route and calcinated at various temperatures (600[Formula: see text]C, 800[Formula: see text]C, 1000[Formula: see text]C, and 1200[Formula: see text]C), we have investigated its phosphors nature in this study. We evaluated the phase purity and grain size distributions from the powder X-ray diffraction patterns of all the samples. This was done using the Rietveld refinement and the FW[Formula: see text]/[Formula: see text]M technique. Our observation of the [Formula: see text] nanoparticles grain size distribution was made possible using transmission electron microscopy pictures and HRSEM images. The photoluminescence spectrum of [Formula: see text] nanoparticles showed emission in the region near-band-edge blue and green emission. To detail the photoluminescence behavior, the excitation, emission spectra and CIE 1976 plot were recorded and the CIE coordinates were found to be [Formula: see text] as well as [Formula: see text] that look like blue. The use of phosphors nature is enabled by studying the impact of grain size and the linear dependent behaviour of [Formula: see text] nanoparticles.

Serrated flow stress in the CoCrFeNi multi-principal element alloys with different grain sizes and added Re

Multi-principal element alloys have attracted extensive attention as a new alloy design concept. In particular, the CoCrFeNi alloys with low stacking fault energy have excellent tensile plasticity and fracture toughness at both low and room temperature, and good phase stability at high temperatures, considered a new type of structural material with great potential. Multi-principal element alloys exhibit plastic instability termed serrated flow, at certain strain rates and temperature ranges. The serrated flow stress is usually closely related to dynamic strain aging, which reflects dislocation and barrier processes and impacts the mechanical properties of alloys. In the present study, CoCrFeNi alloys were selected as the research object, and the impact of grain size and the addition of Re elements on the serrated flow stress behavior was investigated. The results showed that in the tensile tests at 600 °C, the serrated flow stress behavior occurred in the fine-grain specimen only at a lower strain rate. The tensile curves of the coarse-grain specimen at different strain rates all show serration. Overall, the serrated type changes with the decreasing grain size, the increasing strain rate, and the addition of Re element, all of which result in a decrease in the magnitude and number of serrations and a weakening of the serrated behavior.

Static and dynamic fracture toughness of graphite materials with varying grain sizes

Graphite materials play critical roles as moderators, reflectors, and core structural components in high-temperature gas-cooled nuclear reactors. During the reactor operation, graphite materials may experience a variety of loads, including thermal, radiation, fatigue, and dynamic loads, potentially leading to crack initiation and propagation. Therefore, it is imperative to investigate their fracture properties. Despite this, there remains a paucity of comprehensive studies on the fracture toughness of graphite materials with varying grain sizes, particularly concerning dynamic fracture toughness. This study addresses this gap by employing a digital-image-correlation-based virtual extensometer to analyze crack propagation in graphite materials of different grain sizes, enabling precise measurement of crack propagation length and fracture toughness. Findings reveal that static fracture toughness increases with larger grain sizes, while under dynamic loading, smaller grain sizes exhibit greater fracture toughness. Additionally, dynamic fracture toughness shows a near-linear increase with impact speed. Scanning electron microscopy analysis of fracture surface morphology highlights the impact of grain size and impact speed on fracture toughness. Nuclear graphite specimens with larger grain sizes have more irregular grain and pore distributions, enhancing crack deflection and propagation resistance, thereby increasing fracture toughness. The observed loading rate dependence of dynamic fracture toughness is attributed to a gradual transition from intergranular to transgranular fracture modes with increasing impact speed.

Tensile deformation of fine-grained Mg at 4K, 78K and 298K

The impact of grain size, ranging from 0.9 μm to 9 μm, on the mechanical properties of commercially pure Mg is investigated at temperatures of 4K, 78K, and 298K. The mechanisms governing plastic flow are influenced by both grain size and temperature. At 4K and 78K, dominant deformation modes in Mg involve dislocation glide and extension twinning, regardless of grain size. The interactions between basal and non-basal dislocations and dislocations with grain boundaries promote an unusually high rate of work hardening in the plastic regime, leading to premature failure. The yield stress follows the Hall-Petch relationship σy∼k/d, with the slope k increasing with decreasing temperature. At 298K, in addition to dislocation glide and twinning, grain boundary sliding (GBS) becomes significant in samples with grain sizes below 3 μm, considerably enhancing the material’s deformability. GBS activation provides an additional recovery mechanism for dislocations accumulating at grain boundaries, facilitating their absorption during sliding and rotation. Analysis of σΘ relationship suggests that the basal slip is the dominant dislocation mode in Mg at 298K. Decreasing grain size suppresses dislocation activity and twinning and increases GBS, resulting in lower Θ and σΘ values. Suppressing conventional deformation modes coupled with enhanced GBS yields stress softening, breaking down the Hall-Petch relationship in Mg below 3 μm grain size, leading to an inverse Hall-Petch behaviour. The work reports new data on the strength, ductility, work hardening and fracture behaviour, and their variations with Mg grain size across different temperature regimes.

Enhanced energy storage performance in Pb-free Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3-based relaxor ferroelectric ceramics through a stepwise optimization strategy

This study employed a stepwise optimization strategy, including doping Sr(Ga0.5Nb0.5)O3 (SGN) into 0.65Na0.5Bi0.5TiO3-0.35Sr0.7Bi0.2TiO3 (NBT-SBT) ceramics to modify the composition and a further processing improvement. By introducing Ga3+ and Nb5+ ions with high ionic polarization rates into the B-site, the average polarization of the unit cell was maintained while further inducing local disordered fields and promoting polar nanoregions. The high activity of the polar nanoregions was confirmed using piezoelectric microscopy. The effective energy storage density (Wrec) of 2.73 J/cm³ was obtained when the SGN doping was 6.5 %. Subsequently, the densification of ceramics was improved through viscous polymer processing, thereby enhancing the breakdown strength (BDS). A combined approach of finite element simulation and experimental studies was further utilized to investigate the impact of grain size on the BDS. The stepwise optimization strategy enabled the NBT-SBT-6.5SGNVPP ceramics to achieve the Wrec of 5.2 J/cm3 and efficiency (η) of 85 % under 350 kV/cm. Additionally, the ceramics developed by this strategy possess excellent temperature and frequency stability and pulse discharge performance, making them potential candidates for practical applications.

Modeling the impact of grain size on device characteristics of Sb2Se3 solar cells

In this paper, we developed an analytical model to study the impact of grain size and the associated electrical parameters on the device characteristics and spectral response of Sb2Se3 antimony solar cells. Current-voltage characteristics as well as internal and external quantum efficiencies of the cell were modelled and the impact of grain size, effective intra-grain diffusion length, surface recombination velocity at grain boundaries, and carrier lifetime have been investigated. The profile of Electric field at the grain boundaries, the impact of grain size on the performance parameters of the cell have been investigated and the intra-grain diffusion length as an effective parameter on device performance parameters has been studied. The results indicate that a larger grain size is essential for surpassing recombination loss and improving the open-circuit voltage while a better carrier collection and spectral response can improve the short-circuit current density. A practical outcome of our study confirms the necessity of post-deposition surface passivation of Sb2Se3 absorber layers to surpass the recombination loss at grain boundaries and develop larger grains from an optimized deposition process to enhance the carrier collection for a more efficient and stable Sb2Se3 solar cell.

Investigation of the effect of morphological and crystallographic textures on the ductility limits of thin metal sheets using a CPFEM-based approach

The current contribution investigates the effect of some relevant microstructural parameters (specifically, morphological and crystallographic textures) on the ductility limits of polycrystalline aggregates using the Crystal Plasticity Finite Element Method (CPFEM). The polycrystalline aggregates are assumed to be representative of thin metal sheets and their macroscopic behavior is determined from that of their constituent single crystals on the basis of the periodic homogenization technique. The single crystal behavior is described by a finite strain elastoplastic framework in which the plastic flow rule obeys the classical Schmid law and plastic deformation is solely attributed to the slip on the crystallographic slip systems. The CPFEM is implemented within and in connection with ABAQUS/Standard finite element code. The ductility limits are predicted by the Rice bifurcation theory where strain localization is detected when the macroscopic acoustic tensor becomes singular. Three grain morphologies (namely, cube, random, and elongated morphology) and three initial crystallographic textures (namely, cube, random, and copper orientation) are considered to investigate the effect of morphological and crystallographic textures on the onset of plastic strain localization. The numerical results indicate that the effect of initial crystallographic texture is much more pronounced than that of grain morphology on the predicted ductility limits. In addition, the impact of grain size and sheet thickness are thoroughly analyzed. The research reveals that the trends of the predicted ductility limits are strongly dependent on the size effects.

The Effect of Porous Media Grain Size on non-Darcy Flow Behavior using Pore Scale Simulation

The impact of grain size of the porous media of the 3D images of a beadpack on the permeability values and non-Darcy flow behaviour is analyzed using pore-scale flow modelling utilizing the finite volume method. In this study, the sample used was a 3D image from random tight packing of spheres (beadpack) with a size of 250×250×250 voxels and a porosity of 0.36. Variation in grain size is carried out by upscaling the 3D image sample, so that this treatment affects the specific surface area value but does not change the porosity and tortuosity of the sample. Several variations of grain diameter include 100 μm, 125 μm, 150 μm, 175 μm, and 200 μm. In this study, we adopted PIMPLE algorithm, which combines SIMPLE and PISO algorithms to accomplish the Navier-Stokes equations of fluid dynamics in such porous media. The simulation results show that the permeability value exhibits an inverse relationship with the specific surface area. This correlation is in accordance with the Kozeny-Carman equation. In addition, the initiation of non-Darcy flow occurs at the reference length-based Reynolds number of 2.06 and the permeability-based Reynolds number of 0.049.

Experimental and simulated microplastics transport in saturated natural sediments: Impact of grain size and particle size

Microplastics (MPs) present in terrestrial environments show potential leaching risk to deeper soil layers and aquifer systems, which threaten soil health and drinking water supply. However, little is known about the environmental fate of MPs in natural sediments. To examine the MPs transport mechanisms in natural sediments, column experiments were conducted using different natural sediments and MPs (10–150 µm) with conservative tracer. Particle breakthrough curves (BTCs) and retention profiles (RPs) were numerically interpreted in HYDRUS-1D using three different models to identify the most plausible deposition mechanism of MPs. Results show that the retention efficiency for a given particle size increased with decreasing grain size, and RPs exacerbated their hyper-exponential shape in finer sediments. Furthermore, the amounts of MPs present in the effluent increased to over 85 % as MPs size decreased to 10–20 µm in both gravel and coarse sand columns, while all larger MPs (125–150 µm) were retained in the coarse sand column. The modeling results suggested that the blocking mechanism becomes more important with increasing particle sizes. In particular, the attachment-detachment without blocking was the most suited parameterization to interpret the movement of small MPs, while a depth-dependent blocking approach was necessary to adequately describe the fate of larger particles.

Grain size and lattice compatibility enhanced figure-of-merit in Ba0.95Ca0.05Ce0.005ZrxTi0.995−xO3 material for pyroelectric energy conversion

Phase-transforming ferroelectric materials have attracted significant attention due to their potential for energy conversion from waste heat. Here, we explore the impact of grain size and lattice compatibility on the energy conversion figure-of-merit (FOM) of a phase-transforming ferroelectric system Ba0.95Ca0.05Ce0.005ZrxTi0.995−xO3 with Zr content ranging from 0.004 to 0.03. The results demonstrate that tuning grain size and lattice compatibility can significantly increase the FOM. The optimal composition Zr0.006 exhibits the highest FOM among its neighboring compositions, with a corresponding peak pyroelectric current density of 5.6 μA/cm2 generated from a temperature fluctuation of 30 °C at a temperature rate of 5 °C/s. This work provides a rational understanding of the effect of grain morphology and crystal structure on the pyroelectric properties for energy conversion.

Microstructure evolution and mechanical properties of brazing joint for ultra-thin-walled Inconel 718 considering grain size effect and brazing temperature

The systematic investigation of the mechanical properties and microstructure evolution process of ultra-thin-walled Inconel 718 capillary brazing joints is of great significance because of the exceptionally high demands on its application. To achieve this objective, this study investigates the impact of three distinct brazing temperatures and five typical grain sizes on the brazed joints’mechanical properties and microstructure evolution process. Microstructural evolution analysis was conducted based on Electron Back Scatter Diffraction (EBSD), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), High-Resolution Transmission Electron Microscopy (HRTEM), and Focused Ion Beam (FIB). Besides, the mechanical properties and fracture behavior were studied based on the uniaxial tension tests and in-situ tension tests. The findings reveal that the brazing joint’s strength is higher for the fine-grain capillary than the coarse-grain one, primarily due to the formation of a dense branch structure composed of G-phase in the brazing seam. The effects of grain size, such as pinning and splitting, are amplified at higher brazing temperatures. Additionally, micro-cracks initiate around brittle intermetallic compounds and propagate through the eutectic zone, leading to a cleavage fracture mode. The fracture stress of fine-grain specimens is higher than that of coarse-grain due to the complex micro-crack path. Therefore, this study contributes significantly to the literature by highlighting the crucial impact of grain size on the brazing properties of ultra-thin-walled Inconel 718 structures.

Impact of Aggregate Grain Size on ASR-Induced Expansion.

Alkali-silica reaction (ASR) is a sequence of complex chemical processes, resulting in the formation of alkali silica gels with high swelling ability. ASR leads to the expansion of concrete and the degradation of its microstructure. The susceptibility of aggregates to alkali reaction depends, among other factors, on the type and origin of the aggregate, the presence of reactive forms of silica, the mineral composition, and the geometric properties of the aggregate, such as shape and grain size. This study aimed to investigate the impact of the grain size of polymineral post-glacial gravel aggregate, originating from the northern regions of Poland, on its susceptibility to ASR. The expansion of mortars made from polymineral aggregate and the cracking of grains and cement matrix due to the occurring reactions were analyzed. Based on the conducted research, it was observed that the expansion of mortars depends on the grain size of the aggregate. It was demonstrated that the fraction of reactive aggregate generating the most significant elongation of mortars is in the range of 1.0-2.0 mm. The reaction of silica with alkalis continued until the depletion of reactive components in the aggregate. The relationship between the progress of corrosive processes and the grain size of the aggregate was evident in the form of different linear elongation increments of mortars over time. The expansion of mortars was caused by the swelling ASR gel, inducing stress in the grain and the surrounding cementitious paste.

Magnetocaloric effect in nanocrystalline Sm0.5Ca0.15Sr0.35MnO3Compounds: Enhancement of relative cooling power

This study explores the magnetic and Magnetocaloric Effect (MCE) in nanocrystalline Sm0.5Ca0.15Sr0.35MnO3 compounds, with a focus on enhancing the Relative Cooling Power (RCP). Our study indicates that the physical properties get drastically modified due to the reduction of the particle sizes. By investigating the impact of grain size on the MCE and RCP, this research aims to optimize cooling efficiency. The findings highlight the potential of doped manganite nanocrystalline materials as cost effective and environmentally friendly alternatives for advanced cooling technologies.

Impact of Grain Size and Grain Nature in Thin‐Film Solar Cells

Herein, a theoretical investigation is conducted on grain‐size inhomogeneity's impact and grain boundaries’ (GBs’) electrical nature in thin‐film solar cells. Using the Matthiessen rule, grain‐size‐dependent mobility is derived in polycrystalline material. The obtained grain‐size‐dependent mobility values are fed into the Poisson solver to calculate device performance. The severity of grain sizes in the lower region determines how grain size affects the photovoltaic performance by grain‐size‐dependent efficiency simulation. Low grain sizes become critical, especially for low‐thickness absorbers. The second aspect of the study assesses potential variation at GBs to reveal the impact of the electrical properties of GBs. Evidence shows that the acceptor defects at GB are benign for device performance, causing upward band bending at the GB and acting as electron barriers. Device performance is adversely affected by donor defects at GBs due to downward band bending. As summarized in the findings, the polycrystallinity‐induced cause–effect relationships of grains are likely to interest solar cell researchers.