Pulverization Process Research Articles

Edible Electronic Components Made from Recycled Food Waste

AbstractA procedure is developed for producing basic electronic components utilizing materials sourced from discarded orange, grapefruit, lemon, apple, banana, potato, and carrot peels. Initially, these materials undergo dehydration, followed by a meticulous pulverization process to obtain fine powder. Natural adhesives like water, honey, sugar, starch, and gelatin are employed to interconnect the materials. Formed substrates are characterized using Scanning Electron Microscopy, Energy Dispersive X‐ray Spectroscopy, and an optical profilometer. Furthermore, the relative permittivity of the materials is determined. Three distinct types of substrates, derived from the aforementioned peels, are crafted in varying dimensions. Substrates measuring 4 cm × 2.5 cm host interdigital capacitive sensors, whereas larger 6 cm × 3.5 cm substrates accommodate inductor‐capacitor (LC) sensors. Each of the six samples undergoes individual dry testing, while LC sensors are additionally tested with the post‐application of artificial saliva and mouthwash liquids. The sensor's characterization involves measurement of impedance and phase angle for all samples. Capacitance is additionally measured for capacitors, and inductance for LC circuits. These assessments are carried out within the frequency range spanning from 1 MHz to 400 MHz. The objective is the development of fully functional electronic components, derived from discarded edible items, fostering sustainable practices, and finding applications in biomedicine.

Simulation Analysis and Multiobjective Optimization of Pulverization Process of Seed-Used Watermelon Peel Pulverizer Based on EDEM

To enhance the utilization of seed-used watermelon peel and mitigate environmental pollution, a hammer-blade seed-used watermelon peel crusher was designed and manufactured, and its structure and working parameters were optimized. Initially, the seed-used watermelon peel crusher and seed-used watermelon peel model were constructed, and the model’s parameters were calibrated. Subsequently, the discrete element method (EDEM2022) was employed to investigate the effects of spindle speed (MSS), the number of hammers (NCB), and feeding volume (FQ) on the pulverizing process. Multivariate nonlinear regression prediction models were developed for the percentage of pulverized particle size less than 8 mm (Psv), pulverizing efficiency (Ge), and power density (Ppd), followed by the analysis of influencing factors and prediction models using ANOVA. The multiobjective optimization of the prediction model utilizing the improved hybrid metacellular genetic algorithm CellDE resulted in solutions of 90.02%, 89.57%, and 8.35 × 10−3 t/(h-kw) for Psv-opt, Ge-opt, and Ppd-opt, respectively. The corresponding optimal interaction values of MSS, NCB, and FQ were determined to be 1500 r/min, 108, and 150 kg/min. Finally, a prototype test was conducted by combining the optimal factor interaction values, yielding statistically calculated values of 96.63%, 92.37%, and 7.76 × 10−3 t/(h-kw) for Psv-pr, Ge-pr, and Ppd-pr, respectively. The results indicate that the optimized values of Psv-opt, Ge-opt, and Ppd-opt models have an error of less than 8% compared to the statistically calculated values of the prototype test and outperform the values of Psv-ori, Ge-ori, and Ppd-ori obtained under the original parameters.

Droplet deposition of agrochemical spraying: Comparison of results from a random‐walk model and CFD simulations

AbstractThe effectiveness of agricultural spraying processes depends considerably on the ability of the atomized droplets to reach the target site in the desired amount. In this work, two mathematical models to study the trajectories and deposition of atomized droplets are implemented and compared. On the one hand, a computational fluid dynamics (CFD) coupled with discrete phase model (DPM) is implemented to calculate the trajectories of atomized droplets and determine distances at which the droplets are deposited. The continuous phase (atmospheric air) is modelled by continuity, momentum, and energy equations. On the other hand, a Lagrangian random‐walk (LRW) model based on force and energy balances to predict the pulverization process of a nozzle is formulated and implemented in Python. Both models take into account the effects of drag, gravity, buoyancy, and evaporation on individual droplets, as well as the impact of atmospheric stability and dispersion. By tracking a large number of trajectories, meaningful estimates of dispersal statistics can be obtained. The LRW model accurately replicated the trajectories, deposition distances, and final diameters of atomized droplets for three atmospheric stability cases, compared with CFD simulation results. The results of both models agreed that 100 μm droplets were most susceptible to wind‐induced spray drift, depositing at the furthest distances from the nozzle. In addition, 50 μm droplets exhibited a significant tendency to evaporate entirely before reaching the ground. The LRW model is found to be a cost‐effective alternative for estimating spray drift compared to the computationally intensive CFD approach.

Mechanical Performance of Rotationally Molded Multilayer mLDPE/Banana-Fiber Composites.

The incorporation of materials different from the polymer within the rotational molding process usually results in lowered mechanical properties, where impact strength is of particular concern. In order to overcome this issue, multilayer structures of virgin polyethylene (PE) and banana fiber composites were prepared to determine the impact of the different layers on the performance of the final part. Cycle time has been studied to identify the influence of the addition of fibers in the process. The tensile, flexural and impact properties have been analyzed, finding improvements in Young's modulus of up to 13%, although at the expense of significant decreases in impact strength. A reduction in the fiber size due to the pulverization process was observed, which affected the rheological and mechanical behavior of the composite. The beneficial effects of working in multiple layers have been demonstrated in this work, where composites with up to 5% of banana fiber have been produced in two-layer structures. Finally, the need to add neat polyethylene in the external layer is also highlighted as a way to counteract the reductions in mechanical properties, particularly for flexural elastic modulus and tensile strength, and this also helps with the drop in impact behavior to a lower extent.

Dolostone pulverization induced by coseismic rapid decompression of CO2-rich gas in nature (Matese, Apennines, Italy)

South Matese, Apennines, is a hydrothermally and seismically active extensional area characterized by CO2 outgassing and Mw≤7.1 earthquakes. There, meters-sized pockets of incohesive pulverized dolostone are hosted within Mesozoic carbonates at the hanging wall of seismically active normal faults. The aim of this paper is to understand the pulverization process. The pulverized dolostone is finely comminuted (down to a few microns), but primary structures, mainly bedding, are preserved. The grain size distribution is similar to that of previously studied pulverized rocks associated with active faults and dissimilar to that of carbonate cataclasites and fault gouges. The pulverized pockets are surrounded by zones (halos), in which the loose grains are cemented, in their original position, by microcrystalline calcite, resulting in a cemented micro-mosaic breccia. Stable isotopes from the cement are compatible with calcite precipitation from rapidly CO2-degassing shallow waters. Comparing our observations with results of laboratory experiments on carbonate pulverization through rapid decompression of pore-hosted CO2, the best explanation for the pulverized dolostone may lie on local accumulations of pressurized CO2-rich gas, suddenly decompressed during earthquakes. The limited permeability of the gas-saturated dolostone must have prevented a prompt escape of the gas from the rock, which was therefore anhydrously pulverized by the rapid expansion of the trapped gas. The sudden decompression must have suctioned bicarbonate-rich groundwaters, from which microcrystalline calcite rapidly precipitated, fossilizing the freshly pulverized dolostone. Calcite precipitation formed an impermeable shield around the pulverized pockets, which, therefore, remained internally uncemented. This process may have occurred over multiple cycles at depths shallower than the CO2 subcritical–supercritical boundary (ca. -800 m). Although hypothetical, the proposed mechanism is for the first time suggested for an active tectonic environment. The gas rapid decompression could have been triggered by coseismic processes (e.g., dynamic unloading or transient tensile pulses) previously proposed for the formation of other pulverized rocks. The presented case may improve our knowledge of possible chemical-physical processes connected with the subsurface storage of CO2 in seismically active areas.

Fumed Silica-Based Ultra-High-Purity Synthetic Quartz Powder via Sol-Gel Process for Advanced Semiconductor Process beyond Design Rule of 3 nm.

Fumed silica-based ultra-high-purity synthetic quartz powder was developed via the sol-gel process to apply to quartz wares and quartz crucibles for use in advanced semiconductor processes. The process conditions of preparing potassium silicate solution, gelation, and cleaning were optimized, i.e., the relative ratio of fumed silica (10 wt%) to KOH (4 wt%) for potassium silicate solution, gelation time 3 h, and cleaning for 1 h with 5 wt% HCl solution. It was observed that the gelation time strongly affected the size distribution of the quartz powder; i.e., a longer gelation time led to a larger size (d50) of the synthesized quartz powder: 157 μm for 2 h and 331 μm for 5 h. In particular, it was found that the morphology of the as-synthesized quartz powder greatly depended on the pulverizing process; i.e., the shape of quartz powder was shown to be rod-shaped for the without-gel-pulverizing process and granular-shaped with the process. We expect that the fumed silica-based ultra-high-purity quartz powder with an impurity level of 74.1 ppb synthesized via the sol-gel process is applicable as a raw material for quartz wares and crucibles for advanced semiconductor processes beyond the design rule of 3 nm.

Unknown system dynamics estimator based coordinated control of the ultra supercritical boiler‐turbine unit with coal pulverizing delay for large load accommodation

AbstractThe ultra‐supercritical boiler‐turbine unit is required to accommodate large‐range load following to maintain the stability of grid frequency. However, the input delay in the coal pulverizing process poses a challenge to the coordinated control of the boiler‐turbine unit, which is always neglected in existing works but dramatically affects the stability of steam pressure and temperature. In this paper, to handle the delay caused by coal pulverizing, a predictor‐based delay compensation structure is developed for producing a delay‐free control framework for the throttle steam pressure. Moreover, to overcome intrinsic nonlinearities in the dynamics of the boiler‐turbine unit, the unknown system dynamics estimator is employed in the controllers' design for the steam enthalpy in the separator and active power of the turbine. Thus, precise and fast regulation for the active power output can be achieved under wide load following task. The salient merit of the proposed control is that the overshot of the throttle steam pressure and the specific enthalpy in the separator can be significantly alleviated, which is necessary for turbine blade. A Lyapunov‐Krasovskii functional is introduced to deal with the time delay in the stability proof. Finally, the proposed coordinated control is validated in three typical working scenarios.

A Bioengineering Approach for the Development of Fibroblast Growth Factor-7-Functionalized Sericin Biomaterial Applicable for the Cultivation of Keratinocytes.

Growth factors, including fibroblast growth factor-7 (FGF-7), are a group of proteins that stimulate various cellular processes and are often used with carriers to prevent the rapid loss of their activities. Sericin with great biocompatibility has been investigated as a proteinaceous carrier to enhance the stability of incorporated proteins. The difficulties in obtaining intact sericin from silkworm cocoons and the handling of growth factors with poor stability necessitate an efficient technique to incorporate the protein into a sericin-based biomaterial. Here, we report the generation of a transgenic silkworm line simultaneously expressing and incorporating FGF-7 into cocoon shells containing almost exclusively sericin. Growth-factor-functionalized sericin cocoon shells requiring simple lyophilization and pulverization processes were successfully used to induce the proliferation and migration of keratinocytes. Moreover, FGF-7 incorporated into sericin-cocoon powder exhibited remarkable stability, with more than 70% of bioactivity being retained after being stored as a suspension at 25 °C for 3 months. Transgenic sericin-cocoon powder was used to continuously supply biologically active FGF-7 to generate a three-dimensionally cultured keratinocyte model in vitro. The outcomes of this study propound a feasible approach to producing cytokine-functionalized sericin materials that are ready to use for cell cultivation.

Experimental study on geometric parameters of pore structure and quantitative evaluation of complexity of pulverized coal with different metamorphic degrees

In order to quantify pore structure complexity of coal, the low pressure argon adsorption method (LP-ArGA) was used to study geometric parameters of pore structure and quantitative evaluation of complexity of pulverized coal. The results showed that the geometric parameters of pore structure of most single-particle coals showed an obvious downward trend with the decrease of particle size, indicating that the pore structure became simpler in the pulverization process. The weight value of equivalent matrix scale is the largest, which is 0.4871, indicating that it has the greatest influence on pore structure complexity. With the decrease of particle size, the composite evaluation index of complexity of 1#, 2#, 3#, 4#, 5# and 6# samples decreased by 52.4%, 61.1%, 86.3%, 42.1%, 74.6% and 39.9%, respectively. It indicated that particle size has an extremely influence on pore complexity characteristics of single-particle coal. With the decrease of particle size, the pore complexity characteristics of coal samples tended to be simple, on the contrary, they showed medium or complex characteristics. The model has important guiding significance for evaluating the same coal sample with different particle sizes, but there are still some deficiencies for different coal samples.

In Situ Synthesis and Dual Functionalization of Nano Silicon Enabled by a Semisolid Lithium Rechargeable Flow Battery.

Nanosized silicon has attracted considerable attentions as a new-generation anode material for lithium-ion batteries (LIBs) due to its exceptional theoretical capacity and reasonable cyclic stability. However, serious side reactions often take place at the nanosized silicon/electrolyte interface in LIBs, where critical electrochemical properties such as initial Coulombic efficiency (ICE) are compromised. On the basis of this feature, a new method is developed to synthesize nanosilicon-based particles in a facile, scalable way, which are endowed with the function of prelithiation and storage stability in air. A semisolid lithium rechargeable flow battery (SSFB) technology is used for the first time to convert the micrometer-sized silicon raw material into an amorphous-nanosilicon-based material (ANSBM), as a result of the pulverization process induced by the repeated lithiation/delithiation cycles. The particle size is successfully reduced from 1-4 μm to around 30 nm after cycles in the flow battery. Bulk functionalization of the nano silicon is introduced by the unbalanced lithiation/delithiation cyclic process, which endows ANSBM with a unique prelithiation capability universally applicable to different anode systems such as nanosized Si, SiOx, and graphite, as evidenced by the significantly improved ICEs. Superior air stability (10% relative humidity) is exhibited by ANSBM due to surface functionalization by the stable interfacial layer encapsulated by electron-conductive carbon. The outcome of this work provides a promising way to synthesize dual-functionalized nano silicon with good electrochemical performance in terms of improved capacity and increased initial Coulombic efficiency when it is composited with other typical anode materials.

Fine powders from dyed waste wool as odor adsorbent and coloration pigment

Herein, waste dyed wool was transferred into wool powder (WP) using a mechanical pulverization process. This powder benefits from the rich exposed functional groups and porous structures, which endow WP with capacities to adsorb odor molecules. WP milled for 6 h exhibited improved properties including homogeneous surfaces, small mean particle size (3.63 μm) and increased surface area, contributing to its highest odor ammonia adsorption capacity (2.65 mg g−1) and removal rate (91%) among all tested samples. Loading with WP endows cotton fabrics (CF) with greatly improved deodorizing properties and vivid color. WP-coated CF displayed improved ammonia removal properties compared to pristine CF, achieving 65.71% adsorption rate. The K/S value of WP-coated CF reached 1.844 at o.w.f.% of 15. Coated fabrics also showed stable color fastness to washing. This study paves the way for using powders from waste as both odor adsorbent and coloring pigment for fabric functionalization.

Effect of Analytical Particle Size on Pore Structure of High Volatile Bituminous Coal and Anthracite Using Low-Pressure N2 and CO2 Adsorption

To investigate the effect of analytical particle size on pore structure, mesopore (2-50 nm) and micropore (<2 nm) characteristics of high volatile bituminous coal and anthracite with different particle size were determined using low-pressure N2/CO2 adsorption analyses. Mesopore structure parameters in the two coals increase with decreasing particle size, which are attributed to the opening of closed mesopores during the pulverization process. The closed mesopores with different pore size ranges are opened with a certain percentage in high volatile bituminous coal, but opened irregularly in anthracite during pulverization. Micropore structure parameters of the two coals show different variations with decreasing particle size, which are not related to the reconstituted micropore structure. Mineral matter contributes more mesopores than organic matter in anthracite and exerts the negative effect on micropore in the two coals. An evolution model is established to elaborately describe the change of pore structure during the pulverization process, where mineral matter plays a mediating role in the effect of particle size on pore structure.

Study on dynamic response model of elastic support roller rolling on coal layer

Coal-fired power generation is expected to continue to be used in the future. In this process, coal must first be pulverized, and vertical roller mills are used. However, during the pulverization process, abnormal vibration called self-excited vibration rarely occurs. In previous study, a small element testing machine was used to investigate this problem. The relationship between the slip ratio and the coefficient of friction between the roller and the powder showed a characteristic change when abnormal vibration occurred, but it is not clear whether this is the cause of the self-excited vibration. To investigate whether the characteristic relationship between the slip ratio and friction coefficient observed during abnormal vibration is a cause of self-excited vibration, a simulation model was created by applying the relationship between the slip ratio and friction coefficient in the experiment to a mechanical model for a small element testing machine and comparing the results with those of the experiment. As a result, the model was able to represent the vibration frequency that was confirmed in the experiment when abnormal vibration occurred. However, the dependence of the roller horizontal acceleration on the running speed could not be confirmed. The relationship between the slip ratio and the coefficient of friction could not be reproduced, but the change in the coefficient of friction could be reproduced. The vibration modes that are observed when abnormal vibration occurs were confirmed, but it is not clear whether they can be regarded as self-excited vibration or not.

High-quality ground tire rubber production from scrap tires by using supercritical carbon dioxide jet pulverization assisted with diphenyl disulfide

This study presents a high-quality ground tire rubber (GTR) production technology by using supercritical carbon dioxide jet pulverization. Diphenyl disulfide was incorporated as the devulcanization reagent during the pulverization process. The effects of rubber swelling on particle size distributions, shape characteristics, thermal degradation behaviors, and devulcanization behaviors of the acquired GTR were investigated. The results showed that fine pulverization of scrap tires can be achieved, along with a desired degree of rubber devulcanization. Rubber swelling or devulcanization was associated with the failure pattern of rubber under jet impact and was not beneficial for fine pulverization. Rubber devulcanization mechanisms included radical and oxidation-based reactions, both of which showed breakage selectivity of crosslinks. The excellent properties of the acquired GTR can help to achieve good dispersion and enhanced interfacial compatibility with the polymeric matrix. Therefore, supercritical carbon dioxide jet pulverization incorporated with diphenyl disulfide is a promising recycling technology for scrap tires.

Low cost and highly sensitive flexible pressure sensor based on branched micro-structures

Highly sensitive and flexible sensor is an essential component for the development of wearable electronic device and medical equipment. For the property optimization of piezoresistive sensors, the key is to properly design conductive networks, which in principle should be both deformed readily and reversibly upon external load/unload. However, the preparation of such high-performance sensor generally involves complex physiochemical process, and more importantly, high sensitivity is generally realized at the cost of stability, thus limiting its practical applications. In this paper, conductive powders with branched micro-structures are prepared via facile dip-coating polyurethane sponge with graphene oxide, followed by reduction and pulverization. Thin film sensor consists of those conductive powders without any polymeric binder, which provides high structure stability and high sensitivity (125.5 kPa−1), owing to the branched micro-structure as well as the significant increasing number of contract points resulted from pulverization process. After 3000 cycles of deformation, the sensor can still maintain stable signal detection with negligible drift. The combination of high sensitivity, cycling stability and low cost of our sensor could greatly expand its practical applications.

Fabrication of carbon cloth supported Ni@Fe double hydroxide based electrode for flexible supercapacitor applications

Herein, we have decorated the nickel-iron hydroxide (Ni@Fe LDH) directly on the carbon cloth (CC) to fabricate a flexible and binder-free electrode for electrochemical applications. The samples produced were characterized by versatile physical techniques to investigate the surface area, crystallographic structure, chemical composition, and morphology. The Ni@Fe LDH/CC electrode exhibited the high gravimetric capacitance (Cg) of 984 Fg-1 at 1 Ag-1 that is the result of the synergistic effect of hybrid composition, higher surface area, porous structure, and binder-free design. The fabricated electrode showed astonishing cyclic stability, as it retains nearly 87.6% of the initial capacity after 7000 consecutive galvanostatic charge-discharge (GCD) experiments. The best experimental cyclic activity is accredited to the flexible substrate, layered morphology, and porous architecture of the fabricated electrode that protects it from the expected pulverization and expansion processes. Additionally, our flexible and binder-free electrode showed excellent rate-performance and lost just 13.5% gravimetric capacitance when the applied current density value is changed from 1 to 9 Ag-1. In fact, numerous voids and pores of the Ni@Fe LDH sample act as ion-reservoirs and facilitate mass transport even at the higher current density. The electrochemical results ensure that our flexible electrode, thanks to its integrated capacitive performance, has the potential for practical applications in flexible energy storage systems.

Enhanced interfacial reaction of silicon carbide fillers onto the metal substrate in carbon nanotube paste for reliable field electron emitters

Adhesion of carbon nanotube (CNT) onto a cathode substrate is very crucial for field electron emitters that are operating under high electric fields. As a supporting precursor of CNT field emitters, we adopted silicon carbide (SiC) nano-particle fillers with Ni particles and then enhanced interfacial reactions onto Kovar-alloy substrates through the optimized wet pulverization process of SiC aggregates for reliable field electron emitters. As-purchased SiC aggregates were efficiently pulverized from 20 to less than 1 micro-meter in a median value (D50). CNT pastes for field emitters were distinctively formulated by a mixing process of the pulverized SiC aggregates and pre-dispersed CNTs. X-ray photoelectron spectroscopy studies showed that the optimally pulverized SiC-CNT paste-emitter had a stronger Si 2p3/2 signal in the Ni2Si phase than the as-purchased one. The Si 2p3/2 signal would represent interfacial reaction of the SiC nano-particle onto Ni from the CNT paste and the Kovar substrate, forming the supporting layer for CNT emitters. The optimal paste-emitter even in a vacuum-sealed tube exhibited a highly reliable field emission current with a high current density of 100 mA cm−2 for over 50 h along with good reproducibility. The enhanced interfacial reaction of SiC filler onto the metal substrates could lead to highly reliable field electron emitters for vacuum electronic devices.

Confined pulverization promoting durable pseudocapacitance for FeOOH@PEDOT anode in Li-ion battery

β-FeO1-xOHClx (β-FeOOH) with 2 × 2 tunnel structure and high theoretical capacity over 1000 mAh g−1, is a potential candidate for fast charging anodes for Li-ion batteries. However, low electrical conductivity and poor structure stability leading to inferior rate performance and short life span restrict its further application. In this paper, conductive poly(3,4-ethylenedioxythiophene) (PEDOT) polymer supported and coated FeOOH rods ([email protected]) was synthesized by a facile one-pot fmethod. Lots of nanopieces with abundant active sites were formed during conversion reaction. The coating structure of [email protected] provided closer electrical contact for the pulverized FeOOH particles. Therefore, the confined pulverized particles with high surface area and good electrical conductivity adopt fast pseudocapacitive reaction kinetics to realize high rate performance. Consequently, [email protected] composites as Li ion anodes exhibit extended cycle life and enhanced rate capability. This work reveals that conductive polymer confined pulverization process could realize fast and durable storage for converse-type anodes.

Prepration and Properties of Blue Tungsten Oxide Nanopowders by High Energy Ball-Mill

The purpose of this study is to prepare WO3 nanopowders by high-energy milling in mixture gas (7 % H2+Ar) with various milling times (10, 30, and 60 min). The phase transformation, particle size and light absorption properties of WO3 nanopowders during reduction via high-energy milling are studied. It is found that the particle size of the WO3 decreases from about 30 μm to 20 nm, and the grain size of WO3 decreases rapidly with increasing milling time. Furthermore, the surface of the particles due to the pulverization process is observed to change to an amorphous structure. UV/Vis spectrophotometry shows that WO3 powder with increasing milling times (10, 30, 60 min) effectively extends the light absorption properties to the visible region. WO3 powder changes from yellow to gray and can be seen as a phenomenon in which the progress of the color changes to blue. The characterization of WO3 is performed by high resolution X-ray diffractometry, Field emission scanning electron microscopy, Transmission electron microscopy, UV/Vis spectrophotometry and Particle size analysis.

Effect of Particle Size on Pore Characteristics of Organic-Rich Shales: Investigations from Small-Angle Neutron Scattering (SANS) and Fluid Intrusion Techniques

The sample size or particle size of shale plays a significant role in the characterization of pores by various techniques. To systematically investigate the influence of particle size on pore characteristics and the optimum sample size for different methods, we conducted complementary tests on two overmature marine shale samples with different sample sizes. The tests included small-angle neutron scattering (SANS), gas (N2, CO2, and H2O) adsorption, mercury injection capillary pressure (MICP), and field emission-scanning electron microscopy (FE-SEM) imaging. The results indicate that artificial pores and fractures may occur on the surface or interior of the particles during the pulverization process, and some isolated pores may be exposed to the particle surface or connected by new fractures, thus improving the pore connectivity of the shale. By comparing the results of different approaches, we established a hypothetical model to analyze how the crushing process affects the pore structure of overmature shales. Our results imply that intact wafers with a thickness of 0.15–0.5 mm and cubic samples (~1 cm3) are optimal for performing SANS and MICP analyses. Meanwhile, the 35–80 mesh particle size fraction provides reliable data for various gas physisorption tests in overmature shale. Due to the intrinsic heterogeneity of shale, future research on pore characteristics in shales needs a multidisciplinary approach to obtain a more comprehensive, larger scale, and more reliable understanding.