Grain Structure Research Articles

Generating Input Data for Microstructure Modelling: A Deep Learning Approach Using Generative Adversarial Networks.

For the generation of representative volume elements a statistical description of the relevant parameters is necessary. These parameters usually describe the geometric structure of a single grain. Commonly, parameters like area, aspect ratio, and slope of the grain axis relative to the rolling direction are applied. However, usually simple distribution functions like log normal or gamma distribution are used. Yet, these do not take the interdependencies between the microstructural parameters into account. To fully describe any metallic microstructure though, these interdependencies between the singular parameters need to be accounted for. To accomplish this representation, a machine learning approach was applied in this study. By implementing a Wasserstein generative adversarial network, the distribution, as well as the interdependencies could accurately be described. A validation scheme was applied to verify the excellent match between microstructure input data and synthetically generated output data.

Dust/ice mixing in cold regions and solid-state water in the diffuse interstellar medium

Whether ice in cold cosmic environments is physically separated from the silicate dust or mixed with individual silicate moieties is not known. However, different grain models give very different compositions and temperatures of grains. The aim of the present study is to compare the mid-infrared spectra of laboratory silicate grain/water ice mixtures with astronomical observations to evaluate the presence of dust/ice mixtures in interstellar and circumstellar environments. The laboratory data can explain the observations, assuming reasonable mass-averaged temperatures for the protostellar envelopes and protoplanetary disks, demonstrating that a substantial fraction of water ice may be mixed with silicate grains. On the basis of the combination of laboratory data and infrared observations, we provide evidence of the presence of solid-state water in the diffuse interstellar medium. Our results have implications for future laboratory studies investigating cosmic dust grain analogues and for future observations trying to identify the structure, composition and temperature of grains in different astrophysical environments. Laboratory spectra of dust/ice aggregates are comparable to those observed in astrophysical environments, questioning the traditional onion-like layered ice model. According to observational spectra, such icy mixtures could harbour water ice in the diffuse interstellar medium, as well as in low-temperature circumstellar environments.

Highly crystalline MAPbI3 perovskite grain formation by irreversible poor-solvent diffusion aggregation, for efficient solar cell fabrication

Energy efficient synthesis providing high quality crystalline thin films are highly desired in many applications. Here we devise a non-toxic solvent approach for production of highly crystalline MAPbI 3 perovskite by exploiting diffusion aggregation processes. Isopropanol solution based methylammonium lead triiodide (MAPbI 3 ) is used in this context, where the crystal growth initiation starts in an unstable suspension far from equilibrium and the subsequent crystallization is driven by the solubility parameters. The crystal formation is monitored by scanning transmission electron microscope (STEM), observing small crystallization centers growing as time evolves to large grains with high crystal purity. Energy dispersive X-ray spectroscopy (EDS) in STEM mode revealed a Pb rich core-shell structure in newly formed grains. Nano-beam Electron Diffraction (NBED) scan defined PbI 2 crystallites in the Pb rich shell with a single crystal MAPbI 3 core in newly formed grains. After a week stirring, the same aggregated suspension exhibited grains with only single crystal MAPbI 3 structure. The NBED analysis shows a kinetically slow transition from a core shell structure to a single crystal grain. This research presents an impactful insight on the factors that may cause sub-stoichiometric grain boundary effects which can influence the solar cell performance. In addition, the structure, morphology and optical properties of the perovskite grains have been presented. A powder of highly crystalline particles was subsequently prepared by evaporation of the solvent in a low-vacuum oven. Thin film MAPbI 3 solar cells were fabricated by dissolving the powder and applying it in a classical fabrication route. The MAPbI 3 solar cells gave a champion efficiency of 20% (19.9%) and an average efficiency at approximately 17% with low hysteresis effects. Here a strategy to manufacture the material structure without toxic solvents is highlighted. The single-crystal growth devised here opens both for shelf storage of materials as well as a more flexible manufacturing of devices. The process can likely be extended to other fields, where the intermediate porous framework and large surface area would be beneficial for battery or super capacitor materials. • A non-toxic solvent approach for production of high quality MAPbI 3 perovskite grains. • Nano-beam electron diffraction scan on PbI 2 crystallites and single crystal MAPbI 3 grains. • The porous framework of grains and large surface area would be beneficial for energy storage. • Low hysteresis effects and high efficiency for the perovskite solar cells.

Evolution of the Vagran Gold-Bearing Placer Cluster (Northern Urals) and Prospects for Revealing Bedrock Mineralization

Abstract—More than 10 t of gold have been mined within the Vagran placer cluster (Northern Urals), and the identified primary sources are limited to single noneconomic ore occurrences. Our research has established the heterogeneity of placer gold, which reflects the multistage history of the cluster’s development and the diversity of bedrock mineralization owing to which placer deposits were formed. In the structure of the placers, three age stages are distinguished, reflecting the Post-Paleozoic history of the Ural fold belt’s development: (1) Mesozoic–Early Cenozoic peneplanation, formation of areal weathering crusts, disintegration of primary gold sources and formation of linear erosional–structural depressions, which accumulated material from the displaced weathering crusts; (2) orogenic Pliocene–Quaternary stage of tectonic activation and erosion of primary sources and intermediate gold accumulators; (3) the formation of the modern topography, hydronetwork, and alluvial placers. In morphology, chemical composition, and internal structure of grains, five types of native placer gold have been identified, three of which reflect the structure of the main primary source, which is now almost completely eroded; the fourth bears traces of hypergene changes that occurred at the stage of peneplanation and in the development zones of erosional–structural depressions. The fifth type, which has typomorphic features of near-provenance gold, characterizes the mineralization exposed at the final stage of development of the morphostructure of the Ural belt of tectonic–magmatic activation. Reconstruction of the stages of development of the Vagran ore-placer cluster makes it possible to assess the existing placer potential and the prospects for identifying economic primary mineralization.

Magnesium and silicon in interstellar dust: X-ray overview

Context.The dense Galactic environment is a large reservoir of interstellar dust. Therefore, this region represents a perfect laboratory to study the properties of cosmic dust grains. X-rays are the most direct way to detect the interaction of light with dust present in these dense environments.Aims.The interaction between the radiation and the interstellar matter imprints specific absorption features on the X-ray spectrum. We study them with the aim of defining the chemical composition, the crystallinity, and structure of the dust grains that populate the inner regions of the Galaxy.Methods.We investigated the magnesium and the silicon K-edges detected in theChandra/HETG spectra of eight bright X-ray binaries, distributed in the neighbourhood of the Galactic centre. We modelled the two spectral features using accurate extinction cross-sections of silicates, which we measured at the synchrotron facility Soleil, France.Results.Near the Galactic centre, magnesium and silicon show abundances similar to the solar ones and they are highly depleted from the gas phase (δMg> 0.90 andδSi> 0.96). We find that amorphous olivine with a composition of MgFeSiO4is the most representative compound along all lines of sight according to our fits. The contribution of Mg-rich silicates and quartz is low (less than 10%). On average we observe a percentage of crystalline dust equal to 11%. For the extragalactic source LMC X-1, we find a preference for forsterite, a magnesium-rich olivine. Along this line of sight we also observe an under-abundance of siliconASi∕ALMC= 0.5 ± 0.2.

Investigation of Size Effects Due to Different Cooling Rates of As-Quenched Martensite Microstructures in a Low-Alloy Steel

Martensite transformation is a complex mechanism in materials that is classically initiated by a suitable heat treatment. This heat treatment process can be optimized based on a better understanding of the physical mechanisms on the length scale of several prior austenite grains. It is therefore appropriate to consider individual process steps of heat treatment in isolation. The aim of this study is to characterize the microstructural size changes caused by a variation of the cooling rate applied during the quenching process. For this purpose, individual martensitic microstructures from different heat treatments are analyzed using the electron backscatter diffraction (EBSD) method. With special orientation relationships between the parent austenite and martensite, the structure of the prior austenite grains and the close packet plane packets can then be reconstructed. The influence of the heat treatments on these characteristics as well as on the martensite blocks is thus quantified. No significant influence of the quenching rate on the sizes of martensite blocks and packets could be found.

Abnormal Grain Growth: A Potential Way to Construct Gradient Structure

Abnormal grain growth (AGG) has been commonly observed but the mechanism still remains unclear. In this study, the formation of abnormally large grains was investigated in compressed nickel powders. By periodical sintering in the large volume press, AGG occurred and resulted in a gradient coarse-grained structure. Through the improvement of the cell assembly by introducing tungsten tablets with a higher shear modulus, the optimized grained gradient structure can be obtained, which arises from tuning the AGG associated with the suppress of deformation. This work would be a potential way to design heterogeneous gradient nanostructured materials with excellent strength and ductility.

Direct processing of PbZr0.53Ti0.47O3 films on glass and polymeric substrates

This work reports on direct crystallization of PbZr0.53Ti0.47O3 (PZT) thin films on glass and polymeric substrates, using pulsed thermal processing (PTP). Specifically, xenon flash lamps deliver pulses of high intensity, short duration, broadband light to the surface of a chemical solution deposited thin film, resulting in the crystallization of the film. Structural analysis by X-ray diffraction (XRD) and transmission electron microscopy show the existence of perovskite structure in nano-sized grains (≤5 nm). Local functional analysis by band excitation piezoelectric spectroscopy and electrostatic force microscopy confirm the presence of a ferroelectric phase and retention of voltage-written polarization for multiple days. Based on structural and functional analyses, strategies are discussed for optimization of pulse voltage and duration for the realization of crystalline ferroelectric thin films. For ∼200 nm-thick PZT films on glass substrates, 500 μs-long pulses were required for crystallization, starting with 100 pulses at 350 V, 10 or 25 pulses at 400 V and in general lower number of pulses at higher voltages (resulting in higher radiant energy). Overall power densities of >6.4 kW/cm2 were needed for appearance of peaks corresponding to the perovskite phase in the XRD. Films on glass processed at 350–400 V had a higher degree of 111-oriented perovskite grains. Higher applied radiant energy (through increased pulse voltage or count) resulted in more random and/or partially 001-oriented films. For ∼1 μm-thick PZT films on polymeric substrates, 10 to 25 250 μs-long pulses at voltages ranging between 200 to 250 V, corresponding to power densities of ∼2.8 kW/cm2, were optimal for maximized perovskite phase crystallization, while avoiding substrate damage.

FORMATION OF CARBON STEEL STRUCTURE DURING HOT PLASTIC DEFORMATION

Purpose. The main purpose of the work is to determine the peculiarities of the development of recrystallization processes of carbon steel austenite depending on the degree of hot plastic deformation and to develop proposals for improving the structural state of the metal of the railway solid-rolled wheel. Methodology. Two carbon steels of a railway wheel with a minimum and maximum carbon content of 0.55 and 0.65 % and other chemical elements within the grade composition of the steel 60 were used as research material. Samples in the form of cylinders with a diameter of 20 mm and a height of 40 mm were heated in a muffle furnace, exposed for a certain time to equalize the temperature across the cross section of the sample. After that, the samples were subjected to hot compression on Instron type test machine. The temperature interval of hot compression of the samples was 950–1100 ºС, with deformation degrees in height in the range of 10–40%. The strain rate was 10-3–10-2sec-1. A standard etching was used to detect the boundaries of the austenite grains. Structural studies were performed using Epikvant type light microscope at magnifications sufficient to determine the structure of austenite grains. The grain size of austenite was determined by the methods of quantitative metallography. Findings. In the case of hot compression of the railway wheel blank, increasing the concentration of carbon atoms only within the grade composition of the steel is sufficient to increase the average austenite grain size, which confirms the proposals to limit the carbon content in the metal of railway wheels. The formation of a certain degree of austenite structural heterogeneity at the cross section of the rim or hub of the railway wheel is due to a change in the development mechanism of recrystallization processes depending on the deformation value. Under conditions of the same degree of hot plastic deformation, the replacement of one-time compression by fractional one is accompanied by a violation of the conditions of formation of the recrystallization nucleus. As a result of the specified replacement of the scheme of hot plastic deformation we obtain reduction in the austenite grain size. Originality. Based on a study of the development of collective recrystallization processes during the hot compression of carbon steel of the railway wheel, it was determined that the increase in carbon content contributes to the austenite grain increase. After hot compression of the wheel blank, the structural inhomogeneity of austenite that occurs is determined by a change in the mechanism of recrystallization processes development. During deformations above the critical degree, the recrystallization nuclei are formed and successively grow, which leads to the structure refinement. In the case of deformations below the critical value, the growth of austenite grains occurs according to the coalescence mechanism, according to which fragments of boundaries with large disorientation angles consistently disappear. Practical value. For austenite grain refining in massive elements of solid-rolled railway wheel we offer to replace one-time hot compression by fractional one.

Differences in starch structure, physicochemical properties and texture characteristics in superior and inferior grains of rice varieties with different amylose contents

The difference between superior grains (SG) and inferior grains (IG) is an important factor that directly determines rice yield and quality. In this study, four varieties with different amylose contents were used to examine differences in the starch structure, physicochemical and functional properties as well as texture characteristics between SG and IG. A higher amylose content (AAC), long chain (degree of polymerization ≥ 37) content, average degree of polymerization, and larger granule size were observed in SG, while the short chain (DP 6–12) content and relative crystallinity showed the opposite result. This resulted in a lower swelling factor, higher gelatinization temperature, retrogradation tendency and harder texture in SG. SG were found to have higher slowly digestible starch (SDS) and resistant starch (RS) contents compared with IG, which means a better functional properties. This study indicated that higher amylose and long-chain amylopectin contents in SG probably degrades the rice eating and cooking qualities but improves functional properties as compared with IG.

The efficiency of sulfur modifier to neutralize toxic gases in sulfur-asphalt concrete technology

Studies of the advantages of sulfur-asphalt concrete with toxic gas emission neutralizers show that the use of neutralizers reduces the amount of emission of these gases and improves the environmental problem of the use of sulfur-asphalt concrete. Zinc oxide and zinc oxide are not effective in neutralizing hydrogen sulfide and sulfur dioxide. Reducing the emission of toxic gases using dolomite and diatomite is due to the ability of carbonates to neutralize sulfur dioxide through chemical reactions, as well as absorb gases into the porous structure of grains. Other considered neutralization reactions and side processes according to the calculations mainly occur. The processes of interaction of neutralizers with toxic gases and secondary processes can proceed according to various chemical reactions, however, chemical reactions with the release of more energy occur predominantly. This is confirmed by experimental studies. As a result of theoretical and experimental studies, a list of effective toxic gas neutralizers has been established, the emission of which occurs when bitumen interacts with a sulfur modifier.

The effect of size on structure and stress in grained films

ABSTRACTMolecular dynamics simulations are carried out to study the evolution of stress during deposition of atoms on the (001) plane of an FCC crystal, using rectangular simulation box with x–y periodic boundary conditions. The system consists of grains and boundaries. In the current study, we consider different values of the grain-to-grain distances and different relative sizes of deposited atoms. The structure was determined by the kinematical scattering theory. The main factors influencing the stress in thin film systems are creating of dislocation and changing the crystalline structure in grains. The deposited atoms can significantly contribute to the total stress. Depending on their size, atoms contribute compressive or tensile stresses to the total stress.This paper is part of a Thematic Issue on The Crystallographic Aspects of Metallic Alloys.

Microstructural, tribological, and texture analysis of friction surfaced Al-Mg-Cu clad on AA1050 alloy

In the present study, the effect of axial feeding rate of the consumable rod was investigated on the microstructure, texture, and tribological characteristics of AA2024 aluminum alloy cladding over AA1050 alloy. Optical metallography and scanning electron microscopy were used to characterize the microstructure of the coating. The texture of the coating was evaluated by macrotexture measurement using X-ray diffraction. The shear punch, microhardness, and dry sliding wear tests were performed to measure the mechanical properties, hardness, and wear characteristics of the coatings, respectively. The results showed that the high cooling rate at the substrate/coating interface resulted in small grain size in this zone, as well as a gradient structure of precipitates and grains form the top to the bottom of the coating. At a high axial feeding rate (200 mm/min), precipitate size and distribution were found to be the dominant factors in the strengthening of the coating. However, at a low axial feeding rate (75 mm/min), the grain size was introduced as the dominant factor in the enhancement of the coating strength and hardness. Furthermore, the results revealed that an increase in coating hardness was accompanied by a decrease in the friction coefficient. For coating with the highest hardness, the friction coefficient (0.45) approached its corresponding value in the consumable rod (0.42). Also, as the axial feeding rate increased, the recrystallization and shear texture in the coating were weakened. The texture weakening can be attributed to dynamic recrystallization, particle-stimulated nucleation, and Zener pinning.

Using vibrational molecular spectroscopy to detect moist heating induced carbohydrates structure changes in cool-climate adapted barley grain

There is limited research to study how moist heating affects internal structure of barley grain on a molecular basis. The objectives of this study were to use vibrational molecular spectroscopy: 1) to determine the moist heating induced changes of barley carbohydrate (CHO) structure on a molecular basis, 2) to study the effects of moist heating on CHO chemical profiles, Cornell Net Carbohydrate and Protein System (CNCPS) subfractions, in situ rumen degradation, and predicted intestinal carbohydrate supply of barley grain; and 3) to reveal the association between molecular structure spectral features and CHO related metabolic characteristics. Barley samples (CDC cowboy) were collected from Kernen Crop Research Farm (Saskatoon, Canada) during two consecutive years. Half of each sample was kept as raw barley and the other half underwent moist heating (autoclaving at 120 °C for 60 min). The molecular spectroscopy (attenuated total reflectance-fourier transform infrared, ATR-FTIR) was used to detect the barley CHO related molecular structure spectral features. Moist heating did not affect carbohydrate related chemical profiles and CNCPS subfractions but it decreased rumen degradable carbohydrate. Rumen undegradable and intestinal digestion of CHO subfractions were not affected by moist heating. The advanced vibrational molecular spectroscopy can be used to detect carbohydrate molecular spectral features. Nutrient utilization prediction using molecular spectral characteristics is warranted and further investigation is encouraged.

Effect of Co and Mn doping on the morphological, optical and magnetic properties of CuO nanostructures

Copper oxide (CuO) is an exciting semiconducting material with interesting structural and optical properties. Transition metal doped-CuO nanostructures have great potential to use in memory device applications. In the present work, we describe in detail, the synthesis of pure CuO, cobalt (Co) and manganese (Mn) doped CuO via low temperature co-precipitation method. Various techniques like; X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Superconducting Quantum Interference Device (SQUID) magnetometer have been utilized to characterize the synthesized nanoparticles. XRD data exhibits a pure monoclinic phase of CuO for all synthesized samples. Surface morphology obtained from FE-SEM clearly shows the presence of cluster-like structure of grains. The magnetic investigations suggest that pure CuO nanoparticles exhibit the superparamagnetic state, which further transforms to antiferromagnetic state with Co doping. However, a peak of sharp intensity (maxima) at T = Tf in ZFC curve in Mn-doped sample gives the evidence of spin glass (SG) behavior.

Deformation of µm- and mm-sized Fe2.4wt%Si single- and bi-crystals with a high angle grain boundary at room temperature

Plasticity in body-centred cubic (BCC) metals, including dislocation interactions at grain boundaries, is much less understood than in face-centred cubic (FCC) metals. At low temperatures additional resistance to dislocation motion due to the Peierls barrier becomes important, which increases the complexity of plasticity. Iron-silicon steel is an interesting, model BCC material since the evolution of the dislocation structure in specifically-oriented grains and at particular grain boundaries have far-reaching effects not only on the deformation behaviour but also on the magnetic properties, which are important in its final application as electrical steel. In this study, two different orientations of micropillars (1, 2, 4 µm in diameter) and macropillars (2500 µm) and their corresponding bi-crystals are analysed after compression experiments with respect to the effect of size on strength and dislocation structures. Using different experimental methods, such as slip trace analysis, plane tilt analysis and cross-sectional EBSD, we show that direct slip transmission occurs, and different slip systems are active in the bi-crystals compared to their single-crystal counterparts. However, in spite of direct transmission and a very high transmission factor, dislocation pile-up at the grain boundary is also observed at early stages of deformation. Moreover, an effect of size scaling with the pillar size in single-crystals and the grain size in bi-crystals is found, which is consistent with investigations elsewhere in FCC metals.

Evolution of charged grains in harmonic force field

AbstractEvolution of the spatial structure of the massive charged grains in the presence of weak linearly space‐dependent external force in a dusty plasma is studied using molecular dynamics simulation. The interaction among the dust grains in the background electron‐ion plasma is described by a modified Yukawa interaction potential that includes both repulsive and attractive ranges. Evolution of the initially homogeneously distributed dust grains is followed until a quasi‐stationary state is reached. Even though the external force is radially highly asymmetric, the final configuration of the charged grains can be a circular crystal. Still driven by the external force, the grains in the crystal execute synchronized oscillations in the direction of the force. The time needed to reach the quasi‐stationary state decreases with increase of the strength of the external force.

Understanding Zn Electrodeposits Morphology in Secondary Batteries Using Multiscale Computational Approach

Zinc (Zn) aqueous rechargeable batteries (ZBs) have shown a tremendous success in various applications due to their environmental friendliness, multi-electron capacity, high abundance, safety and low cost; however, analogous to their Li-ion battery counterparts, they suffer from the dendrite formation leading to decrease in capacity and eventual failure. Despite many studies reporting a good performance and partial dendrites suppression1, there have been no systematic studies of Zn electrodeposits morphology analysis in ZBs.In this contribution, we present the results of a combined density functional theory (DFT) calculations of Zn diffusion through the ZnO surface layer (i.e., solid electrolyte interface – SEI) and the phase-field modeling (PFM) of Zn electrodeposition study. The DFT calculations are performed using commercial code VASP (Vienna Ab initio Simulation Package)2 with the projector augmented wave (PAW)3 Perdew-Burke-Ernzerhof (PBE)4 pseudo-potentials within generalized gradient approximation (GGA)5. The Zn path and migration barriers are evaluated using the Nudged Elastic Band (NEB) method. The PFM6,7 is developed in the open source code MOOSE and is formulated in continuum theory based upon diffusion-conservation laws using partial-differential equations and then discretized using finite element method8 and solved computationally.The DFT calculations are performed to reveal the dominant diffusion pathways, energetics and the corresponding diffusion coefficients associated with Zn diffusion through the SEI. The SEI surface layer on Zn electrode in ZBs primarily consists of ZnO. Correspondingly, two cases are considered, i.e. the Zn diffusion through the ZnO grain boundary (GB) formed between the different ZnO surface orientations and the Zn diffusion through the ZnO bulk grains. It is found that Zn diffusion occurs through the different nano-channels inside grains as well as through the GB. The path and the activation energies of Zn diffusion vary significantly depending upon the structure of grains and GB, as well as the presence of additional Zn atoms corresponding to the current density dependency. However, the general trend is that Zn diffusion in a grain is faster comparing to the ZnO/ZnO GB. Using the DFT calculations the appropriate elastic properties of SEI components are calculated as required by the PFM.The 2D PFM model predicts the Zn morphologies, the Zn ions concentration, the electrostatic potential, the stress and the equivalent plastic strain. Three regimes are investigated, specifically, low, intermediate and high current densities, where different Zn morphologies, such as boulders, mossy and dendritic shape are observed. It is found that the stress has a major influence on the electrodeposition, and vice versa the Zn electrodeposits growth is found to affect the stress distribution significantly. The plastic yielding occurs preferentially at the node of the boulders and through the filaments and mossy structures. In addition, based upon the present PFM results alternative strategies for the inclusion of the stress field in the mean-field electrochemical modeling will be discussed.Furthermore, both the DFT and the PFM results are supported by scanning electron (SEM) and scanning transmission electron microscopy (STEM) to reveal micro and nano-scopic details of Zn electrodeposits as well as the surface ZnO layer.The combined results also provide a basis for development and design of novel strategies against unwanted Zn dendrites formation.

Study of the electric field-induced domain structure transformation in BaTiO3 ceramics by high resolution methods

Ferroelectric domain structure in BaTiO3 ceramics was studied with nanoscale spatial resolution before and after poling by application of the uniform electric field. Complimentary vector piezoresponse force microscopy (PFM) and backscattered scanning electron microscopy allow visualizing domain structure in the individual grains of ceramics and study of the interaction between domains and grain boundaries. Analysis of the vector PFM images after application of electric field was used for characterization of the transformation of polarization direction in domains and domain bands. Collective dynamics of ferroelastic domains under the action of electric field is discussed.

Coda and Intrinsic Attenuations From Ultrasonic Measurements in Tight Siltstones

AbstractWe have performed ultrasonic measurements on tight siltstone samples to obtain thePwave coda and intrinsic attenuations using a single isotropic scattering model and the spectral ratio method. The results indicate that attenuation is predominantly caused by scattering. Intrinsic attenuation increases with gas saturation and permeability and decreases with grain size, whereas coda attenuation is stronger under partial saturation conditions and increases with grain size. Porosity and mineral composition do not have significant effects on attenuation. The triple‐porosity and scattering models are used to simulate the intrinsic and scattering attenuations, respectively. The results show that the intrinsic attenuation is predominately caused by wave‐induced fluid flow between microcracks/micropores and intergranular pores. The model incorporating the scattering effects of microcracks underestimates the scattering loss in the coda, which may thus be better explained by heterogeneities in the clustering structure of grains.