Impact Of Grain Size Research Articles

Modeling study of mesoscale magnetic treatment influencing factors through dynamic softening analysis

In this paper, a new concept of “dynamic softening” is proposed to explain the mechanism of residual stress reduction through “cold” treatment. The impact of grain size, grain boundary width, and grain orientation on the reduction was studied through experimental characterization. To further investigate the relationship between these factors and residual stress reduction, mesoscopic grain, and grain boundary stress reduction were simulated using COMSOL software. The simulation results were validated through macroscopic experiments. The study demonstrates that grain size, grain boundary width, and grain orientation significantly affect residual stress reduction. Specifically, larger grain sizes and narrower grain boundaries are more effective in reducing residual stress within a certain range.

Grain size and scratching depth dependent tribological characteristics of CrCoNi medium-entropy alloy coatings: A molecular dynamics simulation study

In this work, we have investigated the impact of grain size and scratching depth on the tribological behavior of nanocrystalline CrCoNi medium-entropy alloy (MEA) coatings during scratching by molecular dynamics (MD) simulations. Regardless of the grain size, a monotonically increase in both friction coefficient and wear rate with increasing the scratching depth was observed in the nanocrystalline CrCoNi MEA coating. When its microstructure becomes coarser, the friction coefficient becomes lower. As a function of grain size, the evolutions of friction coefficient and wear rate can be divided into three regions, namely high friction coefficient (or wear rate) region in a grain size range of below 6 nm, relatively stable friction coefficient (or wear rate) region in a grain size range of 6–12 nm, and a relatively low friction coefficient (or wear rate) region in a grain size range of larger than 12 nm. According to the MD simulation results, the higher wear rate for a finer CrCoNi MEA coating can be explained by its lower hardness. In contrast, the reduction of friction force was mainly attributed to the scratching induced grain boundary (GB) sliding and dislocation emissions from GBs. Moreover, the scratching induced phase transformation from crystalline to amorphization and plastic deformation mode transitions also affect its tribological properties.

Engineered water repellency for resilient and sustainable pavement systems

ABSTRACT Moisture-related pavement distresses lead to significant damage and recurring maintenance costs with substantial CO2 emissions. Engineering water repellency in pavement soils can help maintain uniform moisture conditions that improve and maintain performance, reduce design speculation, lowering material and construction costs, and emissions. This study examines the impact of grain size on water repellency treatment effectiveness. Soils from U.S. low volume roads and glass beads were treated with organosilane. Results showed effective water repellency, with contact angles ranging from 119.5° to 148.5°. Larger grain size reduced contact angle while increasing surface roughness raised it. Water drop penetration time tests showed no penetration after 2 hours (7200s), regardless of grain size, with breakthrough pressure values declining with larger grain and pore sizes (2kPa - 0.1kPa). This study discusses highlights the importance of considering grain and pore size effects when using water-repellent soils in pavement construction.

Effect of Grain-Size in Nanocrystalline Tungsten on Hardness and Dislocation Density: A Molecular Dynamics Study

We have simulated a series of nanoindentation experiments on nanocrystalline tungsten specimens using a combination of molecular dynamics simulations and the embedded atom method potential. The research aimed to investigate the impact of grain size on the mechanical properties of tungsten. Nanoindentation is a technique used to measure the mechanical properties of materials at a small scale. In this study, the researchers varied the grain size of the tungsten specimens, ranging from 7.9 to 10.5 nanometers. They also applied a loading rate of 3 angstroms per picosecond at a temperature of 300 Kelvin. The study found that as the grain size increased, the hardness increased, and the elastic modulus decreased. Hardness is a measure of a material’s resistance to deformation, and the elastic modulus is a measure of a material’s stiffness. The findings suggest that as the grain size of tungsten increases, the material becomes harder but less stiff. Additionally, the study explored the ways in which nanocrystalline tungsten deformed during nanoindentation. The researchers found that the deformation of the material was primarily due to dislocation activity, which is consistent with previous research on the topic. Overall, the findings of this research provide valuable insights into the mechanical properties of nanocrystalline tungsten and the ways in which the material deforms under stress. These findings could have practical applications in the development of materials for use in various industries.

Grain-size evolution controls the accumulation dependence of modelled firn thickness

Abstract. The net rate of snow accumulation b is predicted to increase over large areas of the Antarctic and Greenland ice sheets as the climate warms. Models disagree on how this will affect the thickness of the firn layer – the relatively low-density upper layer of the ice sheets that influences altimetric observations of ice sheet mass change and palaeo-climate reconstructions from ice cores. Here we examine how b influences firn compaction and porosity in a simplified model that accounts for mass conservation, dry firn compaction, grain-size evolution, and the impact of grain size on firn compaction. Treating b as a boundary condition and employing an Eulerian reference frame helps to untangle the factors controlling the b dependence of firn thickness. We present numerical simulations using the model, as well as simplified steady-state approximations to the full model, to demonstrate how the downward advection of porosity and grain size are both affected by b but have opposing impacts on firn thickness. The net result is that firn thickness increases with b and that the strength of this dependence increases with increasing surface grain size. We also quantify the circumstances under which porosity advection and grain-size advection balance exactly, which counterintuitively renders steady-state firn thickness independent of b. These findings are qualitatively independent of the stress-dependence of firn compaction and whether the thickness of the ice sheet is increasing, decreasing, or steady. They do depend on the grain-size dependence of firn compaction. Firn models usually ignore grain-size evolution, but we highlight the complex effect it can have on firn thickness when included in a simplified model. This work motivates future efforts to better observationally constrain the rheological effect of grain size in firn.

Evaluation of hydrogen diffusion and trapping in nickel Alloy 625 by thermal desorption spectroscopy

This study presents hydrogen diffusion and trapping in the nickel Alloy 625 by employing the hot extraction test and the thermal desorption spectroscopy (TDS) analysis. Combined with electrochemical permeation test, the impact of grain size and grain boundary carbide on hydrogen diffusion are investigated. The results manifeste that the effective hydrogen diffusivity can be expressed as D=1.03×10−7exp(−46.44kJmolRT)m2/s for the sample with a grain size of ∼8 μm. The diffusion activation energy ED for hydrogen is determined as 42.05–48.10 kJ/mol. The activation energy E associated with interstitial sites/elastic field of dislocations and reversible traps is 17.92–20.73 kJ/mol and 24.87–27.13 kJ/mol, respectively. Moreover, the reduction in grain size and the presence of grain boundary carbide can lower hydrogen diffusivity by locally changing the diffusion and trapping behavior of hydrogen.

Mechanisms of Scaling Effect for Emerging Nanoscale Interconnect Materials.

The resistivity of Cu interconnects increases rapidly with continuously scaling down due to scatterings, causing a major challenge for future nodes in M0 and M1 layers. Here, A Boltzmann-transport-equation-based Monte Carlo simulator, including all the major scattering mechanisms of interconnects, is developed for the evaluation of electron transport behaviors. Good agreements between our simulation and the experimental results are achieved for Cu, Ru, Co, and W, from bulk down to 10 nm interconnects. The line resistance values of the four materials with the inclusion of liner and barrier thicknesses are calculated in the same footprint for a fair comparison. The impact of high aspect ratio on resistivity is analyzed for promising buried power rail materials, such as Ru and W. Our results show that grain boundary scattering plays the most important role in nano-scale interconnects, followed by surface roughness and plasma excimer scattering. Surface roughness scattering is the origin of the resistivity decrease for high-aspect-ratio conductive rails. In addition, the grain sizes for the technical nodes of different materials are extracted and the impact of grain size on resistivity is analyzed.

Enhanced corrosion behavior of ultrafine-grained pure titanium in simulated high-temperature seawater

Corrosion behavior of ultrafine-grained (UFG) pure titanium was studied in simulated seawater at high temperature to increase the probability for marine devices. The UFG Ti was prepared by equal channel angular pressing. The grain size was around 450 nm. The results showed that the corrosion current density of UFG Ti was lower than coarse-grained (CG) Ti in 3.5%NaCl solution at 80 °C, and the UFG Ti could resist pitting corrosion preferably. The basal texture of UFG Ti was stronger and the content fraction of TiO2 in the passive film was higher than CG Ti. The enhanced corrosion performance of UFG Ti at high temperature was attributed to the comprehensive impact of grain size, texture and passive film.

Impact of Grain-Coating Clays on Porosity Preservation in Paleocene Turbidite Channel Sandstones: Nelson Oil Field, UK Central North Sea

The Forties Sandstone Member is an important deep-water reservoir in the Central North Sea. The role of depositional characteristics, grain-coating clays, and diagenesis in controlling the reservoir quality of the sandstones is poorly understood. The main aim of the study is to understand the role of depositional characteristics, grain-coating and pore-filling clays, and diagenesis in controlling the reservoir quality evolution of turbidite-channel sandstones. The study employed a multi-disciplinary technique involving thin section petrography and scanning electron microscopy (SEM) to investigate the impact of grain size, clay matrix content, mode of occurrence of grain-coating chlorite and illite, and their impact in arresting quartz cementation and overall reservoir quality in the sandstones. Results of our study reveal that porosity evolution in the sandstones has been influenced by both primary depositional characteristics and diagenesis. Sandstones with coarser grain size and lower pore-filling clay content have the best reservoir porosity (up to 28%) compared to those with finer grain size and higher pore-filling clay content. Quartz cement volume decreases with increasing clay-coating coverage. Clay coating coverage of >40% is effective in arresting quartz cementation. Total clay volume of as low as 10% could have a deleterious impact on reservoir quality. The Forties Sandstone Member could potentially be a suitable candidate for physical and mineralogical storage of CO2. However, because of its high proportion (>20%) of chemically unstable minerals (feldspar, carbonates, and clays), their dissolution due to CO2 injection and storage could potentially increase reservoir permeability by an order of magnitude, thereby affecting the geomechanical and tensile strength of the sandstones. Therefore, an experimental study investigating the amount of CO2 to be injected (and at what pressure) is required to maintain and preserve borehole integrity. The findings of our study can be applied in other reservoirs with similar depositional environments to improve their reservoir quality prediction.

Combustion Macrokinetics of Granulated (Ti + C)–Ni Mixtures. Impact of Grain Size

Combustion Macrokinetics of Granulated (Ti + C)–Ni Mixtures. Impact of Grain Size

Combustion Macrokinetics of Granulated (Ti+C)-Ni Mixtures. Impact of Grain Size

Combustion Macrokinetics of Granulated (Ti+C)-Ni Mixtures. Impact of Grain Size

The Impact of Grain Size on the Hydromechanical Behavior of Mudstones

AbstractThe consolidation behavior of mudstone is controlled by the clay fraction and affects a wide range of deformation and fluid transport processes in accretionary wedge systems. I analyze the compression and permeability behavior of six sediment mixtures based on uniaxial resedimentation and constant rate of strain consolidation data. The sediment mixtures are composed of varying proportions of hemipelagic mudstone and silt‐size silica resulting in clay fractions ranging from 56% to 32% by mass. The hemipelagic mudstone is from Site C0011 drilled seaward of the Nankai Trough, offshore Japan, during Integrated Ocean Drilling Program Expedition 322. I show that porosity and compression index consistently decrease and permeability consistently increases with decreasing clay fraction over vertical effective stresses ranging from 0 to 21 MPa. Backscattered electron microscope images reveal that matrix porosity declines and large, jagged pore throats are being preserved in compaction shadows between silt grains as the clay fraction decreases. I compare the behavior of reconstituted samples with that of intact core and field measurements and interpret that increasing creep with depth and different mudstone fabrics explain differences in their compression curves. Finally, I provide empirical compression and permeability models that describe the evolution of porosity (void ratio) and permeability with vertical effective stress and as a function of grain size. Characterizing the in situ hydromechanical properties of subduction inputs is critical in order to relate input sediments to those at frontal thrust regions and predict pore fluid pressures and compaction‐driven fluid sources within the outer part of the accretionary prism.

Technical note: On the reliability of laboratory beta-source calibration for luminescence dating

Abstract. The dose rate of the 90Sr / 90Y beta source used in most luminescence readers is a laboratory key parameter. There is a well-established body of knowledge about parameters controlling accuracy and precision of the calibration value but some hard-to-explain inconsistencies still exist. Here, we have investigated the impact of grain size, aliquot size and irradiation geometry on the resulting calibration value through experiments and simulations. The resulting data indicate that the dose rate of an individual beta source results from the interplay of a number of parameters, most of which are well established by previous studies. Our study provides evidence for the impact of aliquot size on the absorbed dose in particular for grain sizes of 50–200 µm. For this grain-size fraction, the absorbed dose is enhanced by ∼ 10 %–20 % as aliquot size decreases due to the radial increase of dose rate towards the centre of the aliquot. The enhancement is most variable for 50–100 µm grains mounted as aliquots of < 8 mm size. The enhancement is reversed when large grains are mounted as small aliquots due to the edge effect by which the dose induced by backscattered electrons is reduced. While the build-up of charge dictates the increase of absorbed dose with the increase of grain size, this principle becomes more variable with changing irradiation geometry. We conclude that future calibration samples should consist of subsamples composed of small, medium, large and very large quartz grains, each obtaining several gamma doses. The calibration value measured with small, medium and large aliquots is then obtained from the inverse slope of the fitted line, not from a single data point. In this way, all possible irradiation geometries of an individual beta source are covered, and the precision of the calibration is improved.

A Tale of Two Grains: Impact of Grain Size on Ring Formation via Nonideal Magnetohydrodynamic Processes

Abstract Substructures in protoplanetary disks (PPDs), whose ubiquity was unveiled by recent Atacama Large Millimeter/submillimeter Array observations, are widely discussed regarding their possible origins. We carry out global 2D magnetohydrodynamic (MHD) simulations in axisymmetry, coupled with self-consistent ray-tracing radiative transfer, thermochemistry, and nonideal MHD diffusivities. The abundance profiles of grains are also calculated based on the global dust evolution calculation, including sintering effects. We found that dust size plays a crucial role in the ring formation around the snow lines of PPDs through the accretion process. Disk ionization structures and thus tensorial conductivities depend on the size of grains. When grains are significantly larger than polycyclic aromatic hydrocarbons (PAHs), the nonideal MHD conductivities change dramatically across each snow line of major volatiles, leading to a sudden change in the accretion process across the snow lines and the subsequent formation of gaseous rings/gaps there. Specific layout of magnetic fields can suppress wind launching in certain regions by canceling out different stress components. On the other hand, the variations of conductivities are a lot less with only PAH-sized grains in disks and then these disks retain smoother radial density profiles across snow lines.

Impact of grain size on the optoelectronic performance of 2D Ruddlesden–Popper perovskite-based photodetectors

This paper presents the synthesis of grain size-controlled 2D perovskite films for high-performance photodetectors by combining solvent engineering and hot casting.

Microstructure and Granularity Effects in Electromigration

The persistent advancements made in the scaling and vertical implementation of front-end-of-line transistors has reached a point where the back-end-of-line metallization has become the bottleneck to circuit speed and performance. The continued scaling of metal interconnects at the nanometer scale has shown that their behavior is far from that expected from bulk films, primarily due to the increased influence that the microstructure and granularity plays on the conductive and electromigration behavior. The impact of microstructure is noted by a sharp shift in the changing crystal orientation at the grain boundaries and the roughness introduced at the interfaces between metal films and the surrounding dielectric or insulating layers. These locations are primary scattering centers of conducting electrons, impacting a film’s electrical conductivity, but they also impact the diffusion of atoms through the film during electromigration. Therefore, being able to fully understand and model the impact of the microstructure on these phenomena has become increasingly important and challenging, because the boundaries and interfaces must be treated independently from the grain bulk, where continuum simulations become insufficient. In light of this, recent advances in modeling electromigration in nanometer sized copper interconnects are described, which use spatial material parameters to identify the locations of the grain boundaries and material interfaces. This method reproduces the vacancy concentration in thin copper interconnects, while allowing to study the impact of grain size and microstructure on copper interconnect lifetimes.

Application of Corrected Methods for High-Resolution XRF Core Scanning Elements in Lake Sediments

Contemporary studies emphasize theoretical and analytical aspects of monitoring water quality within lacustrine settings. The X-ray fluorescence (XRF) core scanner provides the most rapid, non-destructive high-resolution elemental measurements for unprocessed sediments. However, the analytical precision of measured elemental composition may be offset due to water content and inhomogeneities in the physical properties of the sediment. A range of calibration approaches developed specifically for converting XRF scanning intensities to element fractions has been made available. Here, two lake sediment-cores retrieved from southwest China were used to evaluate the performance of various calibration methods. In particular, the influence of sediment properties on XRF scanning intensities was assessed by redundancy analyses (RDA) and the generalized additive model (GAM). The results demonstrate that for fine-grained sediments, the impact of grain size results in only minor deviations in the XRF scanning intensities. Water content of the lake sediment was shown to be the most important factor influencing the XRF scanning intensities, especially for light elements (e.g., Al to Fe). Significant decreases in XRF scanning intensities may occur when sediment water content is greater than 47%. We recommend testing the element fractions obtained via conventional techniques throughout the core and applying the multivariate log-ratio calibration for high-resolution XRF scanning elements within lake sediments.

Impact of grain size and reactant ratio on reduction of CO2 to CH4 by alkali metal hydride

This paper aims to investigate the influence of the grain size and the alkali metal hydride (AH, where A = lithium (Li), sodium (Na) or potassium (K))/carbon dioxide (CO2) mole ratio on carbon dioxide reduction-conversion to methane (CH4) through alkali metal hydrides at an intermediate temperature. The result of this investigation shows that the grain size and AH (A = Li, Na or K)/carbon dioxide mole ratio have a considerable effect on the methane mole percentage and output. Compared with the original sample, when the lithium or potassium hydride sample is milled for 2 h, the mole percentage and output of methane increase. When the time for which the lithium or potassium hydride sample is milled is increased from 2 to 48 h, the mole percentage and output of methane change very little. For the sodium hydride and carbon dioxide system, the grain size of the sample has little effect on the methane mole percentage and output. In brief, alkali metal hydride milled for 2 h is enough for the methanation reaction. In consideration of the AH/carbon dioxide mole ratio, the effects on different reaction systems are not consistent. Activated alkali metal hydrides can effectively convert carbon dioxide to methane under various AH/carbon dioxide mole ratios, and the higher the mole ratio of AH/carbon dioxide, the better the methanation of alkali metal hydride with carbon dioxide.

A rationale for the influence of grain size on failure of magnesium alloy AZ31: An in situ X-ray microtomography study

The present study employs in situ X-ray microtomography to characterize the impact of grain size on void nucleation, growth and linkage during tensile loading of magnesium alloy AZ31. It was found that the tensile strain to failure increased almost threefold when the grain size was reduced from 60 to 3 μm. Grain refinement led to reduced twin formation and reduced void growth rates but did not impact markedly on the relationship between strain and the detected void number density. Because the finer grained samples experienced higher strains to failure, greater void number densities were thus detected at failure in these samples. The void volume fraction at failure remained constant despite changing grain size, within error. Final failure occurs via a shear localization and there appears to be a role of void formation in triggering the final shear instability. We thus favour ascribing failure to a void-sheeting type mechanism. Failure is seen to follow rapidly after a critical void volume fraction is attained and this is broadly consistent with predictions made via the application of a simple McClintock model. The higher strains to failure in the present fine-grained samples are thus ascribed chiefly to the lower rates of void growth. The suppression of void growth by grain refinement seen here may explain why finer grain magnesium alloys often display higher tensile ductility.

Impact of sintering conditions and zirconia addition on flexural strength and ion conductivity of Na-β”-alumina ceramics

Na-β”-alumina ceramics are applied as electrolytes in high-temperature Na/NiCl2 and Na/S batteries. Although featuring excellent sodium-ion conductivity in the order of 0.2 S cm−1 at 300 °C, the brittleness associated with ceramic materials makes Na-β”-alumina electrolytes vulnerable to mechanical stresses, e.g. during battery operation. In this study, the impact of grain size and density on the flexural strength of Na-β”-alumina ceramics is investigated. For constant composition but largely varying grain sizes, we report a constant flexural strength of 163 ± 10 MPa for sintering temperatures between 1560 °C and 1620 °C and dwell times ≤ 30 min. Addition of 5 vol % zirconia improves the flexural strength by 30 %, but reduces the conductivity by 15 %. Furthermore, we show that the addition of zirconia reduces the onset temperature of the liquid phase formation during sintering. These findings show promise for using lower sintering temperatures in the presence of zirconia, which is beneficial on an industrial level.