Grain Size Distribution Research Articles

Application of Surfactant Activated Milling for Production of Nd–Fe–B Magnets by PLP Technology

The granulometric composition of Nd–Fe–B powders has been studied in detail after vibratory milling for various times both without and with the addition of siloxane. Sintered magnets were produced by the powder metallurgy method that excluded the pressing of powders. Correlations between the particle size distribution in the initial powders, microstructure of sintered magnets, and their magnetic hysteresis properties have been established. The difference in methods for estimating the size of powder particles by two methods is demonstrated. It is shown that the size distributions of powder particles and magnet grains are bimodal and are described by a superposition of two lognormal distributions.

Stress-Dependent Shear Strength of Resedimented Nile Silty Clay

The variation of clay undrained shear strength with consolidation stresses is of paramount importance to geotechnical engineers. For several decades, the normalized shear strength of clays has been the cornerstone of geotechnical design in many applications, such as staged construction of embankments. Recently, different trends of shear strength dependency on consolidation stresses have emerged indicating nonlinear variation. Resedimentation has been a useful and reliable method to investigate stress dependency by generating lab test specimens of fine-grained soils with a minimum sample to sample variation for benchmark studies. Previous work on resedimented Nile silty clay (RNSC) has shown unique features, such as high sand fraction and contradicting index properties used for soil classification. The shear strength of Nile silty clay (NSC) and the effects of the consolidation stresses are explored through a laboratory program on resedimented samples from material excavated within the Nile River flood plains. A portion of the material was processed using mechanical energy, which exhibited a significant increase in the liquid limit and a larger clay-sized fraction of particles from grain-size distribution tests. The measured engineering parameters are compared with comparable studied soils and established empirical correlations to provide insights on mechanical behaviors of the NSC. NSC is found to have a rapid decrease in the undrained shear strength ratio and a rapid increase in the lateral stress ratio with increasing consolidation stress.

Electroplated ZnO Thin Film: Influence of Deposition Time on Optical and Structural Properties

Zinc oxide (ZnO) thin film, an important n-type semiconductor for various applications, needs to be prepared by a simple and low-cost method. Herein, ZnO thin films with various deposition times (1.25 min, 2.50 min, 5.00 min and 7.5 min) have been successfully fabricated by the electroplating method. The X-ray diffraction analysis demonstrates that the crystal structure of all samples was hexagonal, with the largest crystal size of 28.17 nm and a deposition time of 2.50 min. The scanning electron microscopy (SEM) analysis shows that the deposition time increased along with the more visible size distribution of the crystallite grains and the smaller, more spherical and uniform, compact coating of the substrate. It is found that increasing the deposition time from 1.25 min to 7.5 min leads to an increment of thickness from 0.84 µm to 4.4 µm. The elemental analysis reveals the presence of zinc (Zn) and oxygen (O) without impurities. The optical analysis reveals that the ZnO transmittance was greater than 95% for all deposition times. The highest bandgap energy value of the ZnO thin film is 3.24 eV at a deposition time of 1.25 min. With great optical and structural properties, our ZnO thin film has a big potential to be used for dye-sensitised solar cells (DSSC).

Unsteady numerical simulation of suspended load in relation to grain-size distribution

Unsteady numerical simulation of suspended load in relation to grain-size distribution

Interplay of flow and bed morphology caused by pool-riffle sequence formation without upstream sediment supply in gravel-bed rivers

Pool-riffle sequences (PRSs) are widely distributed in gravel-bed rivers, but their formation regimes under conditions with no sediment supply have not yet been explored. This study selected one field section of PRSs in the East River and measured the bed surface and bedload longitudinally and used these observations to design scaled, variable width flume experiments where we measured feedback of flow and bed morphology under different flows and slopes without a sediment supply. Experimental results show that there exists the critical value of width-depth ratio during PRS formation, corresponding to the aggregated velocity distribution. Meanwhile, the peak value of turbulent kinetic energy easily occurs in the middle riffle under flood discharge conditions, promoting the removal of fine sediment and its transport downstream. The formation and destruction of the periodic armoring layer in the PRS become common without sediment supply. In fact, downstream sorting effect of the armoring layer is the dominant factor to lead the formation-destruction of bed surface, and causes discontinuous surface GSD (grain size distribution) longitudinally in the field. The increase in the flow and slope can effectively promote PRS development, expanding the variation in the lateral sedimentation but shortening the length of pools and riffles. Furthermore, self-maintenance of adjacent riffles and pools response to the lack of sediment supply is faster and more frequent than that with sediment supply, and higher flow can promote incipient sediment and bedload transport on the bed surface. The PRS with variable-width largely increases the influence of sediment supply on the bedload transport, e.g., the increase of bed load transport rate with incoming sediment supply of the PRS is much higher than that of constant-width channel.

Provenance and deposition of a lithified volcanic-rich layer (VRL-5.5) at 5.5 Ma from Central Apennines (Italy)

Two slightly lithified volcanic rich layers (VRL) (former tephra) SVT-2 (San Vittorino) and CAC (Castiglione a Casauria) were sampled from two distinct post-evaporitic Messinian stratigraphic sections (Abruzzo, Central Italy). They crop only few tens of km apart and are predominantly massive, although some specimens show sedimentary structures. Both VRLs were investigated for the first time by field, mesoscopic, X-ray powder diffraction (XRPD), transmission optical microscopy (TOM), scanning electron microscopy (SEM), bulk composition, electron-microprobe analysis (EMPA) and quantitative textural attributes by image analysis. The XRPD analysis detects the presence of a glass phase, plus few (< 2 area %) magmatic-like feldspars, clinopyroxene and biotite and stratigraphically variable sedimentary minerals such as calcite, dolomite, illite and montmorillonite (from 0 to 40 area %). The 2D image analysis performed on SEM microphotographs reveals that both sections are composed of very fine glass shards, magmatic minerals are never isolated, whilst the carbonate crystals mainly fill voids among volcanic particles. Both these VRLs have identical rhyolitic glass compositions that closely overlap with those of previously-studied coeval and stratigraphically related sections occurring in the northern Apennine region and dated as 5.5 Ma. The 2D textural features of glassy particles (length, width, aspect ratio, grain-size distribution, MZ , σi, SKi, KG and roundness) in both SVT-2 and CAC sections are very similar and also close to the northern section of Camporotondo (Marche region). The outcomes provided here indicate that SVT-2 and CAC sections represent the southernmost distal deposits of the same large eruption that occurred about 5.5 Ma (VRL-5.5). They result from distal fallout of tephra through seawater, occasionally remobilised under low energy and localised conditions, especially in the uppermost part of the CAC section. All the VRL-5.5 rocks are probably related to a very large eruption that occurred in the Carpathian-Pannonian magmatic district. The analytical protocols used in this study can be useful to investigate other ancient volcanic-rich layers, corresponding to lithified tephra.

Spatio-temporal variability of hydraulic conductivity in the floodplain riverbank of a hyporheic zone

A detailed measurement of floodplain riverbank sediment hydraulic conductivity (K) is the first step in analyzing the hydraulic relationship between streams and aquifers. Poyang Lake is the largest freshwater lake in China and has historically been a flood-prone area. A detailed field experiment was conducted in the Xiushui River, China, before and after the flood season. The grain-size distribution analysis method was used to determine the hydraulic conductivity of the riverbank. A total of 116 sediment samples were collected from the test site. An in situ permeameter test was used to confirm the consistency of the spatial distribution trend of the estimated hydraulic conductivity based on the grain-size distribution analysis. A Kruskal–Wallis test of the riverbank sediment K values obtained before and after the flood season showed that they belong to different populations. The probability distribution illustrated the strong heterogeneity of the riverbank sediments before and after the flood season. Previous studies have confirmed the presence of strong hyporheic exchange and biological processes at this study site. Following the flood season, the K values had a higher mean, median, and coefficient of variation, confirming that the flood process enhanced the heterogeneity of the riverbank sediments. Overall, the hydraulic conductivity of the three areas changed with distance from the river; the closer the area was to the river, the smaller the hydraulic conductivity and weaker the heterogeneity. An experimental framework of spatio-temporal variability in riverbank sediments is proposed, providing recommendations for researchers on conducting an integrated experiment.

The fragmentation-induced fluidisation of pyroclastic density currents

Pyroclastic density currents (PDCs) are the most lethal volcanic process on Earth. Forecasting their inundation area is essential to mitigate their risk, but existing models are limited by our poor understanding of their dynamics. Here, we explore the role of evolving grain-size distribution in controlling the runout of the most common PDCs, known as block-and-ash flows (BAFs). Through a combination of theory, analysis of deposits and experiments of natural mixtures, we show that rapid changes of the grain-size distribution transported in BAFs result in the reduction of pore volume (compaction) within the first kilometres of their runout. We then use a multiphase flow model to show how the compressibility of granular mixtures leads to fragmentation-induced fluidisation (FIF) and excess pore-fluid pressure in BAFs. This process dominates the first ~2 km of their runout, where the effective friction coefficient is progressively reduced. Beyond that distance, transport is modulated by diffusion of the excess pore pressure. Fragmentation-induced fluidisation provides a physical basis to explain the decades-long use of low effective friction coefficients used in depth-averaged simulations required to match observed flow inundation.

Data-driven time–frequency analysis of nonlinear Lamb waves for characterization of grain size distribution

Nondestructive characterization of grain size distribution is significant for revealing the mechanical properties of metal materials. Traditional linear ultrasonic methods have been applied to estimate mean grain size but are less sensitive to small grain size. Nonlinear ultrasonic technology shows high sensitivity to microstructures, while it unfortunately encounters underdetermined problem in the characterization of microstructures across multiple scales. Combining linear and nonlinear ultrasonic responses would be a quite attractive way to achieve comprehensive observation of microstructural evolution. This work presents a data-driven approach for characterizing grain size distribution using nonlinear Lamb waves. The short-time Fourier transform (STFT) of detected ultrasonic signals were input into a convolutional neural network (CNN) to comprehensively learn the implicit linear and nonlinear dynamics involved with grain size distribution. Multiple convolution kernels slide across the STFT images with multiscale receptive fields to collectively model hierarchical representations and capture local correlation of interesting from time-frequency domain. The trained model achieved 94.7% accuracy in predicting mean grain size, and also achieved 95.4% and 86.3% accuracy in predicting the expectation and standard deviation of the lognormal distribution of grain size, respectively. The visual activation maps demonstrate that local interesting features are successfully captured. In particular, the prediction accuracy was demonstrated to reduce greatly after removing the fundamental frequency and second harmonic from the STFT images, confirming that incorporating linear and nonlinear ultrasonic information is indispensable for accurate characterization of grain size distribution.

Early Cretaceous (late Barremian−Early Albian) expanding aeolian activity in East Asia: Evidence from the stratigraphic evolution of aeolian deposition in the Baiyin-Jingyuan Basin, northern China

Cretaceous aeolian deposition is important for understanding variations of the tropical−subtropical atmospheric circulation under the greenhouse background. Nevertheless, detailed records revealing the response of aeolian deposition to rising atmospheric CO2 are still lacking. To shed light on their linkage, we examined the Early Cretaceous stratigraphic evolution of the Hekou Group in the Baiyin-Jingyuan Basin, northern China, using multiple methods. The results indicate that the lower Hekou Group is characterized by a transition from submerged alluvial to shallow lacustrine deposition. Overlying these facies is loess-like deposition without bedding, distinguished by grain-size distribution, surface microtextures, and geochemical analysis, which is followed by palustrine deposition. In the palustrine deposition, aeolian sand-dune and sand-sheet deposition can be identified, which gradually developed upward in the Hekou Group, with intercalated wet interdunes, damp interdunes, and pebble-sand sheetflood beds. Finally, aeolian sand dunes and sand sheets dominated the upper Hekou Group. Overall, the upward-changing facies indicated the development of aeolian deposition from an aqueous environment, revealing a long-term paleoclimatic shift from semi-humid, semi-arid to extremely arid, which reflects the expanded aeolian activity in East Asia during the Early Cretaceous. Furthermore, various records were combined to investigate the expanding aeolian activity in East Asia, which indicates a west−east-trending arid belt that was wider than the modern counterpart during the late Barremian−Early Aptian and late Aptian−Early Albian, respectively. These stepwise expansions of aeolian activity were mainly driven by rising atmospheric CO2, which strengthened the subsiding branches of Hadley circulation and the subtropical high, eventually leading to intensified aridification.

Corrigendum: Using eruption source parameters and high-resolution grain-size distributions of the 7.7 ka cleetwood eruption of mount mazama (Oregon, United States) to reveal primary and secondary eruptive processes

CORRECTION article Front. Earth Sci., 06 April 2023Sec. Volcanology Volume 11 - 2023 | https://doi.org/10.3389/feart.2023.1182638

Grain size distribution drives microbial communities vertically assemble in nascent lake sediments

Sediment microbes are crucial for maintaining biogeochemical cycles in aquatic ecosystems, yet the influence of sediment geophysical structure on microbial communities remains unclear. In this study, we collected sediment cores from a nascent reservoir in its initial stage of deposition and utilized the multifractal model to comprehensively characterize the heterogeneity of sediment grain size and pore space. Our results demonstrate that both environmental physiochemistry and microbial community structures varied significantly with depth, with the grain size distribution (GSD) being the key driver of sediment microbial diversity, as revealed by the partial least squares path model (PLS-PM) method. GSD can potentially impact microbial communities and biomass by controlling pore space and organic matter. Overall, this study represents the first attempt to apply soil multifractal models into the integrated description of physical structure in sediment. Our findings provide valuable insights into the vertical distribution of microbial communities.

Ceramics Properties of Indurated-Shale Quarry Wastes from Abakaliki, Southeastern Nigeria: Application as Raw Materials in Roofing-Tile Production

AbstractThe present study describes research carried out to evaluate the mineralogical, geochemical and technological properties of indurated shale-quarry wastes and assess the suitability of these low-cost and locally available quarry wastes generated from crushed indurated shales for possible use as alternatives to fresh raw materials in the manufacture of roofing-tile products. Firstly, the mineralogical and chemical properties of the indurated shales were investigated by X-ray diffraction (XRD) and X-ray fluorescence, while their physical properties were identified by grain-size distribution, Atterberg limits, and clay activity. Samples of indurated shale-quarry wastes (ISQWs) were subjected to heat treatment at elevated firing temperatures to provide the required strength and durability and their ceramics properties (linear shrinkage, weight loss, water absorption, bulk density, and flexural strength) were determined. From the results, the ISQWs were composed predominantly of fine particles with medium plasticity and clay activity with values generally &gt;0.75. The mineralogy revealed a predominance of aluminosilicates (illite-kaolinite-smectite-chlorite) with large quartz contents and variable percentages of carbonate and feldspar. The oxides were dominated by SiO2 and Al2O3, small amounts of ferromagnesian minerals, and considerable amounts of alkalis (K2O and Na2O) which act as fluxes. The CaO concentrations were variable and related to carbonate contents. Characterizations based on compositional ternary (total clay mineral-carbonate-quartz + feldspar) systems, Casagrande clay workability charts, and Winkler and McNally diagrams revealed their suitability for ceramics applications as the majority of ISQW samples fell within the specifications for roofing tiles. The ISQWs fired at a high temperature of 1000°C revealed considerable weight loss, reduction in both linear shrinkage and water absorption with insignificant increase in flexural strength. In order to achieve excellent ceramics properties and further reduce sintering temperature for their suitability as raw materials in the production of roofing tiles, beneficiations of ISQWs are highly recommended.

Influence of processing temperature on microhardness evolution, microstructure and superplastic behaviour in an Al–Mg alloy processed by high-pressure torsion

Experiments were conducted to assess the effect of processing temperature on the hardness evolution, microstructure and the flow properties of an annealed Al–3Mg alloy processed by high-pressure torsion (HPT) at either 300 or 450 K. The results demonstrate that HPT processing at room temperature (RT) leads to higher microhardness values with a more uniform hardness distribution in the Al alloy compared with processing at 450 K. After 10 HPT turns at RT, the microstructure displayed a more intense grain refinement, a higher dislocation density and smaller Al3Mg2 precipitates than after HPT at 450 K. Accordingly, the metal processed at RT showed enhanced strength at RT and consistently exhibited superplastic flow during deformation at 523 K, with tensile elongations of ∼530–650% for strain rates from 10−3 to 10−2s−1. Conversely, a maximum elongation of ∼110% was recorded at 523 K in the alloy processed by HPT at 450 K. This behaviour is attributed to an enhanced thermal stability in the metal processed at RT compared with HPT at 450 K where deformation at 523 K led to the onset of abnormal grain coarsening due to a more disperse distribution of grain sizes and the partial dissolution and coalescence of Al3Mg2 precipitates after HPT processing.

Microstructure and tensile strength of electrodeposited Fe-rich bcc FeCoNi medium-entropy alloys

Crystal grain refinement in high- and medium-entropy alloys is an effective approach to obtaining good strength as well as ductility. An FeCoNi medium-entropy alloy with a wide range of grain sizes was fabricated by electrodeposition. The alloy had a metastable bcc structure with Fe–36 at.% Co–21 at.% Ni composition and heterogeneous distribution of grain sizes ranging from 20 nm to 15 µm. Moreover, the alloy possessed a tensile strength of 1.2 GPa, and a fracture elongation of 6.3 % without secondary phase. The excellent mechanical properties of the alloy can be attributed to its bcc phase and heterogeneous grain sizes extending to the nanoscale.

Comparing the quantity and quality of glass, metals, and minerals present in waste incineration bottom ashes from a fluidized bed and a grate incinerator

Bottom ash is the primary solid residue arising from municipal solid waste incineration. It consists of valuable materials such as minerals, metals and glass. Recovering these materials from bottom ash becomes evident when integrating Waste-to-Energy within the circular economy strategy. To assess the recycling potential from bottom ash, detailed knowledge of its characteristics and composition is required. The study at hand aims to compare the quantity and quality of recyclable materials present in bottom ash from a fluidized bed combustion plant and a grate incinerator, both located in the same city in Austria and receiving mainly municipal solid waste. The investigated properties of the bottom ash are grain-size distribution, contents of recyclable metals, glass, and minerals in different grain size fractions, and the total and leaching contents of substances in minerals.The study results reveal that most recyclables present are of better quality for the bottom ash arising at the fluidized bed combustion plant. Metals are less corroded, glass contains fewer impurities, minerals contain fewer heavy metals, and their leaching behavior is also favorable. Furthermore, recoverable materials, such as metals and glass are more isolated and not incorporated into agglomerates as observed in grate incineration bottom ash. Based on the input to the incinerators more aluminum and significantly more glass can potentially be recovered from bottom ash from fluidized bed combustion. On the downside, fluidized bed combustion produces about five times more fly ash per unit of waste incinerated, which is currently disposed of in landfills.

Inhomogeneous deformation substructure and its effect on the recrystallization behavior of yttria dispersion-strengthened tungsten plate

Tungsten materials have been chosen for use in critical parts (i.e., as the armor of plasma-facing material) in fusion reactors. Deformed tungsten will undergo recrystallization at a high-temperature service environment, and recrystallized tungsten exhibits brittleness, which reduces mechanical properties, thermal shock resistance and service lifetime. The deformation heterogeneity may result in an inhomogeneous microstructure, affecting its recrystallization behavior. The main aim of the present work is to qualitatively and quantitatively characterize the heterogeneity in the through-thickness deformed microstructure of an yttria dispersion-strengthened tungsten plate warm-rolled to 50 % thickness reduction ratio and study the effect of heterogeneous microstructure on recrystallization behavior. For this, topological maps of the surface, quarter and center region are measured on the deformed state and annealed state utilizing electron backscatter diffraction (EBSD). Distributions of grain size, geometrically necessary dislocations (GND) energy, potential nuclei density and texture have been analyzed in detail. The results revealed that the deformed microstructure of tungsten plate along full-thickness has no apparent heterogeneity gradient of grain size and texture, but the center layer has a larger subgrain size and more potential recrystallized nuclei compared to the surface layer. The larger subgrain is more conducive to static recrystallization nucleation, while the existing potential recrystallized nuclei can grow rapidly without incubation time during subsequent high-temperature annealing, thereby recrystallization preferentially undergoes in the center layer of the tungsten plate.

Significance of Cu and Cc in Evaluating Internal Stability with Application to Design of Subbase Gradation in Pavements

The hydraulic internal stability is governed by the grain size distribution (GSD) and relative density of unbounded subbase materials. The type of GSD is characterized by the coefficient of uniformity (Cu) and coefficient of curvature (Cc). The internal stability is assessed preliminarily based on the type of GSD with only Cu limits. This study focuses on the practical utility of Cu and Cc in evaluating internal stability of unbounded materials. A relation between Cu and Cc with internal stability is developed based on the functional form of GSD, which depends on three parameters: d10, Cu and Cc. The proposed method is validated with experimental results from published literature and current study, providing a simplified assessment for preliminary investigations. The implications of the internal instability dependent on the Cu and Cc are illustrated for the three unbounded aggregate gradations typically used for subbase in pavements. The advantages of an optimum aggregate gradation with Cu equal to 15 and Cc equal to 1.7 are illustrated for the hydraulic and structural requirements. A gradation band is usually specified for subbase to allow flexibility in selecting the design gradation in standards and design guidelines. The band is constrained to limit the selection of internally unstable gradations and segregation during placement. In this paper, constraints for a gradation band are derived based on the characteristics of the optimum aggregate gradation. The constraints are illustrated with examples for a design of subbase layer gradation band dependent on the subgrade characteristics.

A universal grain‐size distribution of soil with scaling invariance

AbstractSoils are composed of wide‐ranged grains and grain size distribution (GSD) is the fundamental characteristic determining the physical and hydraulic properties. Previously we have proposed a GSD function for various soils. However, the remarkable discrepancy in the distribution occurs in some soils, which not only limits the applicability of the function but also raises doubt as to the possibility of a universal GSD function. In this study we modify the GSD function to a general form of P(D) ~ D−μexp(−D/Dc)n, which introduces a new exponent n for the grain size scale. It turns out that this modification has eliminated the discrepancies and universally applies to a great variety of soils from around the world (hence to be a universal GSD function, UGSD). The exponent n is proved to be a scaling factor of grain size in log‐scale and divides soils into three categories of n &lt; 1 n &gt; 1, and n = 1. Furthermore, soils of surface processes (e.g., erosion, tillage, desertification, landslides, avalanches, deposition, and sediment transportation) remain in the same category and preserve the UGSD function. Thus, the UGSD not only provides parameters μ and Dc as synthetic indices for soil properties (e.g., as indices for spatial heterogeneity or variables for pedotransfer functions), but also describes texture changes in dynamic processes. The UGSD function represents a ‘conservative law’ underlying soil genesis and processes, which fills the knowledge gaps related to the lack of universally applicable indices for soil properties, and thus has universal applications in soil classification, spatial variability, as well as dynamical processes.

Effects of particle morphology on pore structure and SWRC of granular soils

Given grain-size distribution (GSD) and relative density, the soil–water-retention curve (SWRC) of granular soils can be straightforwardly predicted. However, the evolution of SWRC with different particle morphologies under the same GSD is still unclear. To solve this fundamental problem, herein, four sand analogues with different particle shapes under the same GSD were produced by three-dimensional printing. The SWRCs and the pore structure at mesoscale were synergetically measured by using nuclear magnetic resonance (NMR) technology and hydraulic properly analyser water potential meter. The relationship between particle morphology and SWRC was quantitatively analysed, and the soil pore structure evolution under different particle morphology was clearly observed. Compared with round particle shape soils, soils with the same GSD but higher degree of angularity were found to have a subtle higher air-entry value (AEV) at a given relative density, even though the global void ratio is larger. NMR results indicate the pore structure of specimens with different particle morphology is similar. The pore volume is increased with angularity while the maximum pore throat shows an opposite trend. The difference in maximum pore throat is the fundamental reason for the variation in AEV, highlighting the importance of particle morphology on soil–water-retention behaviours.