Range Of Grain Sizes Research Articles

Entrapment in CO2 and H2O Ices: Impact of Ice Matrix Thickness

The volatile inventories of planets depend on the precise partitioning of different volatiles between the gas and solid phases across the planet birth disk. For the case of hyper-volatiles (e.g., CO, N2, and noble gases), the partitioning also depends on how efficiently they are trapped into less volatile ice matrices. The thicknesses of these ice matrices can range from a few molecular layers to macroscopic bodies, and in this study we explore how entrapment efficiency depends on the ice thickness between tens of nanometers and a few micrometers (∼50–3000 monolayers, ML). We carry out a series of temperature-programmed desorption (TPD) experiments on H2O:CO and CO2:CO mixtures with 5:1 and 15:1 matrix-to-CO mixing ratios. Entrapment efficiencies range from 41% to 64%, with higher entrapment efficiencies for the more dilute ices. Surprisingly, we find no significant difference in entrapment across the studied ice thicknesses for either H2O or CO2 ice matrices. Complementary TPD experiments with the additional hyper-volatiles N2 and Ar see a similar trend with ice thickness. We speculate that these results may be due to surface topography such as cracks that lead to hyper-volatile escape from deep ice layers. In either case, these experiments show that entrapment in microscopic ices is relatively insensitive to ice thickness (above ∼50 ML). In protoplanetary disks we therefore expect efficient entrapment in icy grains of a range of grain sizes.

Cliff Notching Due To Swash Abrasion: Insights From Physical Experiments

AbstractNotch development at the base of sea cliffs is an important control on cliff recession rates, but a detailed mechanistic understanding of notch formation by swash abrasion is lacking. We conducted physical experiments, using homogeneous erodible rock simulants, to study notch‐forming mechanisms under periodic sediment‐laden bore impacts. Our findings reveal shifts in the temporal dynamics of notch development. Initially, swash uprush and vortex formation contribute to a positive feedback loop that creates a shallow and wide notch. Subsequently, upward erosion ceases, and notch backwear and downwear are dominated by the vortex. Eventually, sediment deposition armors the notch floor; this negative feedback loop reduces erosion. The sediment size determines the amount of erosion, with a range of grain sizes generating maximum erosion. This indicates a dependence on the momentum of the sediment particles entrained within the bore. This research reveals fundamental notch formation mechanisms driven by swash abrasion.

The impact of crystal grain size on the behavior of disordered ferromagnetic systems: from thin to bulk geometry

We report the findings of an extensive and systematic study on the effect of crystal grain size on the response of field-driven disordered ferromagnetic systems with thin, intermediate, and bulk geometry. For numerical modeling we used the athermal nonequilibrium variant of the random field Ising model simulating the systems with tightly packed and uniformly cubic-shaped, magnetically exchange-coupled crystal grains, conducted over a wide range of grain sizes. Together with the standard hysteresis loop characterizations, we offer an in-depth examination of the avalanching response of the system, estimating the effective grain-size-related exponents by analyses of the distributions of various avalanche parameters, average avalanche shape and size, and power spectra. Our results demonstrate that grain size plays an important role in the behavior of the system, outweighing the effect of its geometry. For sufficiently small grains, the characteristics of the system response are largely unaffected by grain size; however, for larger grains, the effects become more noticeable and show up as distinct asymmetry in the magnetization susceptibilities and average avalanche shapes, as well as characteristic kinks in the distributions of avalanche parameters, susceptibilities, and magnetizations for the largest grain sizes. Our insights, unveiling the sensitivity of the system’s response to the underlying structure in terms of crystal grain size, may prove beneficial in interpreting and analyzing experimental results obtained from driven disordered ferromagnetic samples of different geometries, as well as in extending the range of possible applications.

Microstructure-sensitivity of CPFEM models on fretting fatigue crack initiation of AA2024-T351 alloy

The AA2024-T351 alloy is widely used in civil engineering, machinery, and aerospace industries for bolts, rivets, and thin plate components. When in service within these fields, the components are susceptible to performance degradation and fracture failure due to fretting fatigue. In this study, a crystal plastic finite element method (CPFEM) model incorporating microstructure sensitivity is employed to predict the fretting fatigue crack initiation (FFCI) location and lifetime. The submodel method is utilized to simulate various microstructures in the contact region of the specimen under fretting fatigue. This research focuses on two fatigue indicator parameters (FIPs): accumulated plastic slip p and FIPFS, used to determine the hotspots for crack nucleation on the contact surface and subsurface in fretting fatigue. The study explores the impact of different grain size and orientation on crack nucleation and analyzes how various microstructural characteristics influence the crack initiation lifetime. The findings indicate that the influence of grain orientation distribution in fretting fatigue on the initiation location of contact surface cracks is not significant, but it has a notable impact on subsurface cracks. Different grain textures combinations exhibit a more pronounced anisotropy based on the accumulated plastic slip p than FIPFS. Additionally, the effect of grain orientation distribution on the FFCI lifetime is influenced by the average grain size, showing remarkable influence within a specific range of grain sizes.

The Diatomite Grinding Technology Concept for the Protection of Diatomite Shells and the Control of Product Grading.

Diatomite deposits in Poland are located in the Podkarpackie Voivodeship, and the only active deposit is in Jawornik Ruski. Therefore, it is a unique material. Improved rock processing methods are constantly in demand. In the research presented here, we have used research methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), particle shape analysis, and appropriate sets of crushing machines. Diatomite comminution tests were carried out on test stands in different crushers (jaw crusher, hammer crusher, high-pressure roller press, ball mill) using different elementary crushing force actions: crushing, abrasion, and impact, occurring separately or in combination. The machines were tested with selected variable parameters to obtain products with a wide range of grain sizes ranging from 0 to 10 mm. The ball mill (yield 87%, system C3) and the hammer crusher with HPGR (high-pressure grinding roller) (yield 79%, system D2 + D3) have the greatest impact on diatom shell release and accumulation in the finest 0-5 μm and 5-10 μm fractions. For commercial purposes, it is important to obtain very fine fractions while keeping the shells undisturbed.

Determination of a pedotransfer function for specific air–water interfacial area in sandy soils: A pore network‐informed multigene genetic programming approach

AbstractUnderstanding specific air–water interfacial area (SAWIA) is essential for characterizing and modeling various phenomena in vadose zone hydrology, such as virus and colloid transport, contaminant dissolution, evaporation, and the hydro‐mechanical behavior of unsaturated soils. Traditional measurement methods, including X‐ray imaging and tracer techniques, often encounter challenges, leading to a scarcity of studies that provide a reliable relationship for SAWIA. Currently, no pedotransfer function in the literature links SAWIA with saturation and suction using readily measurable soil properties such as median grain size and porosity. In this study, we initially developed a pore network model capable of predicting SAWIA by calibrating it with corresponding soil‐water retention curves (SWRCs). We then used these models to compile a comprehensive database of SAWIA for six sandy soils, for which experimental SWRCs were available, covering a range of median grain sizes and porosities. Utilizing this database, we established a pedotransfer function through multigene genetic programming. The accuracy of this function was validated against experimental data not previously used in its training and testing. Our parametric study indicated that increases in either porosity or median particle size led to a decrease in the regions exhibiting higher SAWIA in terms of saturation and suction.

Forecasting particle Froude number in non-deposition scenarios within sewer pipes through hybrid machine learning approaches

Sediment deposition has a substantial effect on the hydraulic capacity of channels in urban drainage and sewer systems. In this sense, the self-cleaning concept has been extensively used in the construction of urban drainage and sewer systems. In this regard, the design of the sewer system heavily depends on the accurate forecasting of the particle Froude number (Fr). This study is conducted on experimental data sets collected from existing studies, including a wide range of dimensionless grain size of particles (Dgr), sediment median size (d), hydraulic radius (R), volumetric sediment concentration (Cv), and pipe friction factor (λ) for the condition of clear bed. We forecasted the particle Froude number using four different input combinations. We employed the Random Tree (RT) and Reduced Error Pruning Tree (REPT) methods as standalone methods, as well as Random Committee (RC) and Bagging (BA) methods as hybrid machine learning (ML) methods in particle Froude number forecasting. Hybrid machine learning methods demonstrate enhanced performance compared to both standalone machine learning methods and empirical equations. In the context of sewer system design under non-deposited bed conditions, there is a need to accurately forecast the particle Froude number, RC-RT (IA = 0.96, R = 0.928, MSE = 0.718, RRMSE = 0.197, NSE = 0.86, and PBias = −0.284) performed the best, followed by BA-RT, RC-REPT, BA-REPT, RT, and REPT. In our research, it was found that, in forecasting the particle Froude number under non-deposited bed conditions, Cv emerges as the most responsive input parameter among others.

Size–shape–stable isotope (C and O) relationships of cryogenic cave carbonates formed in permafrost settings

Cryogenic cave carbonates (CCCs) genetically related to permafrost are of special interest in paleoclimate research. Their 230Th/U ages provide unique information about the former presence and depth of permafrost in presently permafrost-free areas. Details of CCC formation processes and their diagnostic features, however, remain incompletely understood. In this paper, we report the results of a study of CCCs from two northern Eurasian caves, currently located in permafrost-free rocks. CCCs in the caves occur in a wide range of grain sizes (micrometers to several centimeters). Stable isotope values of different CCC morphotypes (size range of 0.1 to 4 mm) plot within relatively tight clusters in δ18O-δ13C space, regardless of their grain size, indicating that CCCs of the same morphotype, but of different size, formed simultaneously at certain freezing stages. The clusters conform to an overall negative “freezing trend” in δ18O-δ13C space. The position on the trend indicates the relative age of individual morphotypes; scatter of the data in δ18O-δ13C space suggests multiple episodes of freezing (permafrost formation). The systematic characterization of CCC morphologies and the study of fine-size fractions of CCCs provide important insights into the processes involved in CCC formation in caves located in permafrost.

Optimization of dielectric response in BiFeO3–CoFe2O4 nanocomposites for high frequency energy storage devices

The rapid development of smart and sophisticated miniaturized electronic devices put a high demand for high permittivity material. In the current report, we analyze structural, morphological, and dielectric response of spinel-perovskite composites consisting of CoFe2O4 (CFO) as the spinel phase and BiFeO3 (BFO) as the perovskites phase. Here pristine BFO and CFO are fabricated using Sol—Gel auto-combustion route and their composites with a recipe (1-x) BiFeO3 - (x) CoFe2O4 (x = 0.0, 0.1, 0.2 and 0.3) using solid-state reaction technique. Structural investigation identifies presence of rhombohedral perovskite phase of BFO and cubic spinel phase of CFO and thus guarantees the formation of the composite. The crystallite size increases from 16 to 36 nm for BFO and 39.5–54 nm for CFO. The distribution of well-shaped particles with a reduction in grain size in range of 50–400 nm is witnessed in morphological analysis with the increment of CFO contents in composites. Elemental purity and the presence of various elements according to their stoichiometric ratio are witnessed during elemental investigation. A detailed analysis of the dielectric permittivity, electric modulus, and impedance of these compositions is carried out to investigate their suitability for electronic and energy storage devices. The nanocomposites under study exhibit a dielectric constant of 1126 at 100 Hz for x = 0.3, which decreases to 102 at 1 MHz. Concurrently, the tangent loss for x = 0.3 is observed to be 3.37 at 100 Hz, decreasing to 0.31 at 1 MHz. However, a decrease in dielectric loss and increase in impedance is noticed when the concentration of CFO in BFO nano-composite is increased which reflects the reduction in power losses and better control in electronic conductivity and thus highlights the role of these compositions for advanced energy storage electronic devices.

Lattice variation as a function of concentration and grain size in MgO–NiO solid solution system

The study aimed to understand how changes in crystal's size affect the lattice parameters and crystal structure of Mg1-xNixO solid solution for six X values ranging from x = 0 to x = 1. Mg1-xNixO was synthesized via two different wet-chemical techniques: the sol-gel and the microwave hydrothermal method, both followed by calcination at different temperatures of 673, 873, 1073, 1273 and 1473 K. As annealing caused grain growth, the varied temperature range allowed to examine a wide range of grain sizes. The lattice parameters and x values were determined from XRD (X-ray diffraction) peak positions and intensities respectively. The grain size was evaluated by XRD line profile analysis and supported by SEM (scanning electron microscope) observations. At the temperatures of 673 and 873 K grain size was in the nanometric range and from 1073 K and above grain size was in the micrometric range. A non-monotonic lattice variation versus grain size was found for each concentration. When grain size decreased there was a slight contraction, however for grain size in the nanometric range there was a severe lattice expansion. Both lattice parameter changes were explained by two effects acting together: contraction due to surface stress and expansion due to weakening of the ionic bonding at nanocrystalline particles. In this current research study, the lattice parameter was mapped in two dimensions: concentration and grain size. The findings of this study provided valuable insights into the lattice variation in the MgO–NiO solid solution system.

In-situ EBSD study on twinning activity caused by deep cryogenic treatment (DCT) for an as-cast AZ31 Mg alloy

This work studied the activation of the twins in a commercial cast AZ31 Mg alloy by deep cryogenic treatment (DCT) using in-situ EBSD. The initial as-cast microstructure has a range of grain sizes. The DCT mainly activated twins in the areas of fine grain size, in which the twin area fraction increased with increasing DCT time. These twins were {10–12} extension twins, which were evoked and facilitated by the large tensile interior stress that was caused by the large temperature difference during the DCT. Furthermore, only {10–12} extension twins were activated. The activated {10–12} extension twins had the highest Schmid factor and conformed to Schmidt's law. One or two other kinds of tensile twinning variants of the six tensile twinning variants (V1–V6) were activated by the DCT. These activated variants had the highest Schmid factor and the lowest orientation difference (less than 10o), while those non-activated variants had an orientation difference of ∼60o. Theoretical evaluation indicated that these two kinds of tensile twinning variants were the para-position variant rather than the ortho-position variant or the meta-position variant.

Laser beam shaping facilitates tailoring the mechanical properties of IN718 during powder bed fusion

One of the recent technological developments in the Laser Powder Bed Fusion (LPBF) process is the use of non-Gaussian beam profiles of power density distributions. Irrespective of the strategies used to change the beam profile, spatial beam shaping enhances process flexibility since it allows manipulation of the thermal field, the melt pool shape, and the microstructure. This work showcases the impact of novel ring and conventional Gaussian beams on density, melt pool characteristics, and mechanical properties of IN718 superalloy via LPBF. A novel laser source with beam shaping capabilities provided the beam profiles, ranging from Gaussian to ring beams. The results show clear differences between the crystalline patterns obtained with Gaussian and the other ring beams attempted. This study elucidates the impact of melting modes and solidification mechanisms on the texture index, arising from the interplay between laser beam shape modes and laser speed. It also shows how the crystalline configuration associated with each case studied influences the mechanical properties and how it is possible to modify the process parameters and the beam shape mode to extend control over the mechanical properties of the components manufactured using LPBF. This leads to a broader range of mechanical properties and grain size when tailoring the power density distribution towards ring beams. Additionally, the correlation between melt pool shape geometry, texture index, and mechanical properties is discussed, and the limitations and advantages of each mode are defined.

Controls on terrigenous sediment supply to northwestern South China Sea based on a sediment trap record at Xisha Trough

The South China Sea (SCS) is the largest marginal sea in the western Pacific and comprises an ideal natural laboratory for studying deep-sea processes. Previous investigations in the region have primarily focused on surface currents and to a lesser extent on intermediate currents, while observations of bottom currents are scarce, hindering our understanding of deep ocean sediment transport and deposition mechanisms. Here, we carried out grain size measurement and end-member modelling analysis (EMMA) on samples collected by a sediment trap at a water depth of 1500 m in the Xisha Trough in the northwestern South China Sea. Grain size data shows that terrigenous material has particle sizes ranging from 0.3 μm to 745.9 μm and a peak at 4–11 μm. The EMMA result suggests that finer sediment accounting for an average of 48.2% of the sediment represents material transported by deep water currents (End-member 1; EM1), and this is primary sediment source in the region. Coarser sediment contributing to 32.9% of the sediment is the second most significant source (EM3), representing the deposits of surface currents influenced by monsoons and deposited close to the source. A third sediment type (EM2) constituting approximately 18.9% of the sediment exhibits a wide range of grain sizes and rapid changes, indicating transport in the bottom nepheloid layer triggered by anticyclonic eddies. Our study identifies three primary sediment transport mechanisms to the northwestern SCS, bridging present-day observations with paleoceanography and providing a crucial basis for future research on paleoceanographic reconstructions.

Optimal Constrained Groove Pressing Process Parameters Applying Modified Taguchi Technique and Multi-Objective Optimization

Most engineering problems are complicated, and developing mathematical models for such problems requires understanding the phenomena through experiments. It is well known that as processing parameters with assigned levels increase, so does the number of experiments. By minimizing the number of experiments, Taguchi’s method of experimental design will help to furnish the idea of full factorial experimental design. Taguchi’s method is more appropriate for single-objective optimization problems and needs modifications while dealing with multi-objective optimization problems. Aluminum alloys are in great demand in today’s automotive and aerospace sectors due to their low density, good corrosion resistance, and excellent machinability. The material is subjected to a constrained groove pressing (CGP) process to obtain microstructural grain refinement with enhanced mechanical behavior. This paper considers AA6061 material having major alloys such as silicon and magnesium. For this work, 3 CGP process parameters (viz., displacement rate, plate thickness and number of passes) are assigned 3 levels to each parameter, acquired the test data, viz., grain size (gs), micro hardness (hs), and tensile strength (ult) based on L9 orthogonal array of Taguchi. Using a modified version of Taguchi’s methodology, it is possible to estimate the range of grain size (gs), micro hardness (hs), and tensile strength (σult) for effective combinations of the CGP processing parameters and validate the results with existing test data. A more dependable and simpler multi-objective optimization procedure is used to choose the optimal CGP processing parameters.

Net Transport Patterns of Surficial Marine Sediments in the North Aegean Sea, Greece

The spatial distribution of sediments on the seafloor reflects the various dynamic processes involved in the marine realm. To analyze sediment transport patterns in the North Aegean Sea, 323 surficial samples were obtained and studied. The granulometry data revealed a diverse range of grain sizes of surficial sediments, ranging from purely sandy to clay. The predominant size classes were silt and muddy sand, followed by sandy silt and mud. However, there were very few samples that fell within the clay classes. The sorting coefficient ranged from 0.21 to 5.48, while skewness ranged from −1.09 to 1.29. The sediment transport patterns were analyzed based on the grain-size parameters (mean, sorting, and skewness). The results showed the variability of flow parameters involved in sediment distribution. River influx and longshore drift near the shoreline are the most significant factors affecting sediment transport. At the open sea, sediment distribution is mainly controlled by general water circulation patterns, especially by the outflow of low-salinity waters from the Black Sea through the Dardanelles and the Marmara Sea. The heterogeneity of sediment textural parameters across the study area suggests that seafloor sediments are further reworked in areas where water masses are highly energetic. It can be concluded that open sea water circulation controls sediment distribution patterns at the open shelf, while close to the coast, river discharge plays a key role.

High-pressure studies of size dependent yield strength in rhenium diboride nanocrystals.

The superhard ReB2 system is the hardest pure phase diboride synthesized to date. Previously, we have demonstrated the synthesis of nano-ReB2 and the use of this nanostructured material for texture analysis using high-pressure radial diffraction. Here, we investigate the size dependence of hardness in the nano-ReB2 system using nanocrystalline ReB2 with a range of grain sizes (20-60 nm). Using high-pressure X-ray diffraction, we characterize the mechanical properties of these materials, including bulk modulus, lattice strain, yield strength, and texture. In agreement with the Hall-Petch effect, the yield strength increases with decreasing size, with the 20 nm ReB2 exhibiting a significantly higher yield strength than any of the larger grained materials or bulk ReB2. Texture analysis on the high pressure diffraction data shows a maximum along the [0001] direction, which indicates that plastic deformation is primarily controlled by the basal slip system. At the highest pressure (55 GPa), the 20 nm ReB2 shows suppression of other slip systems observed in larger ReB2 samples, in agreement with its high yield strength. This behavior, likely arises from an increased grain boundary concentration in the smaller nanoparticles. Overall, these results highlight that even superhard materials can be made more mechanically robust using nanoscale grain size effects.

The effect of tooling design and properties of materials on fracture and deformation through equal channel angular pressing technique

The submicrometer range of grain sizes was reached for AA5083 by using equal channel angular pressing at room temperature. While the submicrometer grains of AA5083 were stable up to annealing temperatures of 300 °C, the stability of these grains was only moderately maintained up to annealing temperatures of about 200 °C. Tensile tests conducted after one pass of equal channel angular pressing—that is, strain introduction of roughly one—showed a significant increase in the 0.2% proof stress and ultimate tensile stress values for each alloy. Concurrent with this improvement, the elongations to failure decreased. The analysis shows that the square root of the magnesium content in each alloy corresponds with the magnitudes of these stresses. In samples that were cold rolled, comparable values of proof stresses and ultimate tensile stress were obtained at equivalent strains. However, because of the induction of a very small grain size, elongations to failure were higher after applying equal channel angular pressing to similar strains greater than one. The effects of material constitutive behaviour, tool design, and friction conditions on metal flow, stress fields, and the tendency for tensile fracture during the equal channel angular pressing process were studied using a finite element modelling technique. A degree of non-uniform flow was noted that extended past the head and tail of the extrusion when materials were subjected to equal channel angular pressing with varying constitutive behaviours or when utilising tooling with a radiused front leg. It is anticipated that tool design and material qualities will have a considerable effect on tensile stresses and, in turn, the development of tensile damage during equal channel angular pressing.

A statistical perspective for predicting the strength of metals: Revisiting the Hall–Petch relationship using machine learning

The mechanical properties of a material are intimately related to its microstructure. This is particularly important for predicting mechanical behavior of polycrystalline metals, where microstructural variations dictate the expected material strength. Until now, the lack of microstructural variability in available datasets precluded the development of robust physics-based theoretical models that account for randomness of microstructures. To address this, we have developed a probabilistic machine learning framework to predict the flow stress as a function of variations in the microstructural features. In this framework, we first generated an extensive database of flow stress for a set of over a million randomly sampled microstructural features, and then applied a combination of mixture models and neural networks on the generated database to quantify the flow stress distribution and the relative importance of microstructural features. The results show excellent agreement with experiments and demonstrate that across a wide range of grain size, the conventional Hall–Petch relationship is statistically valid for correlating the strength to the average grain size and its comparative importance versus other microstructural features. This work demonstrates the power of the machine-learning based probabilistic approach for predicting polycrystalline strength, directly accounting for microstructural variations, resulting in a tool to guide the design of polycrystalline metallic materials with superior strength, and a method for overcoming sparse data limitations.

Effect of Grain Size Distribution on Shear Strength Characteristic of Random Fill Material at Keureuto Dam, Indonesia

Earth-fill dams are commonly constructed by composing different geomaterials to optimally utilize local natural resources. In Indonesia, random fill materials are frequently used as a major composition in dam construction. The term random fill material originated from its broad range of grain size. Grain size distribution influences shear strength characteristics of geomaterials. There are 2 shear strength equations to model the behavior of fill material, i.e., linear Mohr-Coulomb and non-linear power curve. Two series of large scale in situ direct shear tests were performed at Keureuto Dam, Indonesia. Sieve analysis tests were performed accordingly. The random fill material was composed of cobbles, gravel, and less than 25% of sand. The stress-displacement characteristics of random fill material indicated that plastic deformation occurred at shear strain of 1% to 4%. The shear failure was reached in shear displacements of 60 – 90 mm, equivalent to shear strain of 8% – 12 %. Stress-strain relationships showed a dilative behavior indicating the random fill was in a relatively dense form. The dilatancy tends to decrease as the normal stress increases. The linear Mohr-Coulomb failure criteria and non-linear power curve equation are suggested to characterize the shear strength of the random fill material. To obtain a realistic value of the non-cohesive strength parameter of granular material, the Mohr-Coulomb approach should be intercepted at zero. A relationship between secant friction angles for different normal stresses is presented. This angle tends to decrease at higher normal stresses.

The Role of Grain Size in the Mechanical Properties of Metals

It is now well established that the grain size is the fundamental microstructural feature of all polycrystalline materials. In practice, a very wide range of grain sizes will be needed in order to fully evaluate the effect of grain size on the mechanical properties of metals. For many years this was a significant limitation because it was not possible to use conventional thermomechanical processing to produce materials with submicrometer or nanometer grain sizes. Recently, this problem has been addressed by developing alternative processing techniques based on the application of severe plastic deformation. This overview demonstrates that, although the flow stress increases with decreasing grain size at low temperatures and decreases with decreasing grain size at high temperatures, this clear dichotomy in behavior may be adequately explained by using a single theoretical flow mechanism based on the occurrence of grain boundary sliding.