Macropore Content Research Articles

Enhanced leaching control of chromium, antimony, and chlorine utilizing CO2-curing slag-fly ash-based agent

This study strives to address the technical bottleneck posed by leaching risks associated with Cr, Sb, and soluble Cl in low-carbon slag-fly ash-based cementitious materials (BFCM) according to our previous research. The introduction of CO2 activation significantly enhances the dissociation of BFS, leading to superior mechanical performance and environmental safety of BFCM. LT3 matrix of BFCM (BFS: MSWI fly ash: FGDG: cement= 42: 20: 10: 28) showed excellent compressive strength (46.79Mpa at 7d). The LT3 matrix enables effective solidification/stabilization (S/S) of Cr, Sb, and Cl with CO2-curing (7d). Furthermore, the leaching concentrations of Sb and Cl within LT system, exhibit a positive correlation, while they demonstrate a negative correlation with Cr. Sb primarily relies on the levels of Ca2+ and OH- in the leaching solution, critical for the formation and stability of Ca-Sb precipitation based Visual MINTEQ fitting. CO2-curing enhances the S/S efficiency of Cl by accelerating the ion exchange of Cl- with OH- in C-A-H and SO42- in the AFm phase, leading to the formation of functional Friedel’s salt. This process is characterized by OH- dissolution and subsequent CaSO4 crystallization. The LT system activated by CO2 exhibited accelerated reaction kinetics relative to traditional hydration (LH), characterized by rapid BFS dissociation and the formation of functional hydration products such as ettringite, C-(A)-S-H, and Friedel's salt. This process also reduced macropores and capillary pores of BFCM, a positive correlation exists between the relative macropore content and Cl leaching levels, whereas the decrease in both macropores and capillary pores is associated with ettringite crystallization.

Pore Structure Characterization and Fractal Characteristics of Tight Limestone Based on Low-Temperature Nitrogen Adsorption and Nuclear Magnetic Resonance

Pore structure characterization and fractal analysis have great significance for understanding and evaluating tight limestone reservoirs. In this work, the pore structure of tight limestone, low-temperature nitrogen adsorption (LTNA), and low-field nuclear magnetic resonance (NMR) are characterized, and the fractal dimension of the pore structure of tight limestone is discussed based on LTNA and NMR data. The results indicate that the pores of tight limestone have H3 and H4 types, the pore size distribution (PSD) of the H3 type is a wave distribution ranging from 2 to 10 nm, and the PSD of the H4 type is a unimodal distribution ranging from 2 to 10 nm. The transverse relaxation time (T2) spectrum of tight limestone shows a single peak (DF), double peak (SF), and triple peak (TF), and the ranges for the T2 spectra for micropores, mesopores, and macropores are 0.1 to 10 ms, 10 to 100 ms, and greater than 100 ms, respectively. The LTNA fractal dimension of tight limestone (DL) ranges between 2.4446 and 2.7688, with an average of 2.5729, and the NMR fractal dimensions of micropores (DNMR1), mesopores (DNMR2), and macropores (DNMR3) are distributed between 0.3744 and 1.1293, 2.4263 and 2.9395, and 2.6582 and 2.9989, respectively. Moreover, there is a negative correlation between DL and average pore radius, a positive correlation between DL and specific surface area, and a positive correlation between DNMR2 and DNMR3 and micropore content, while DNMR2 and DNMR3 are negatively correlated with the content of mesopores and macropores.

New strategy to further enhance the thermal insulation performance of silica aerogel: Decline the macropore content between skeletons

Silica aerogels are considered as promising porous thermal insulation materials. However, the macropores between skeletons in the microstructure prevent further improvement of the thermal insulation performance. Therefore, it is feasible to decrease the macropores content between skeletons to enhance the thermal insulation performance. In this work, we employed Al2O3 nanoparticles as fillers and utilized high-temperature treatment to shrink the skeletons and reduce the macropores content. The experimental results demonstrate that the Al2O3 nanoparticles are well-dispersion within the skeletons and the diameters of macropores dramatically decrease from 7.55 μm to 0.78 μm. The thermal conductivity declines from 0.0821 to 0.0673 W/ (m K). Furthermore, the silica aerogel is treated at high-temperature environment to further reduce the macropores diameters. As a result, the skeleton structure undergoes significant shrinkage. The micropore volume increases from 0.013 to 0.102 cm3 g−1, and the specific surface area increases from 9.828 to 294.4 m2 g−1. The thermal conductivity decreases from 0.0727 to 0.0368 W/ (m K) with the temperature increasing. Theoretical calculations indicate that the attribution of the thermal conductivity reduction is primarily the weakening of gaseous heat transfer below 400 °C. Above 400 °C, the effect of solid heat transfer becomes stronger than the limitation of gaseous heat transfer, which aligns with the experimental results. This study presents novel strategy for enhancing the thermal insulation performance of silica aerogels.

Pore Structure and Factors Controlling Shale Reservoir Quality: A Case Study of Chang 7 Formation in the Southern Ordos Basin, China

The lithofacies types, pore structure differences, and main controlling factors on the shale reservoirs are vital problems that need to be addressed in the process of shale oil exploration and development. This study explores the Luohe oilfield in the southern Ordos Basin, which is composed of organic-rich shale in the Chang 7 member, to clarify the reservoir properties and analyze major factors affecting the reservoir quality. The shale reservoir can be divided into five lithofacies using ternary diagrams of TOC, argillaceous minerals, and siliceous minerals: high organic-rich siliceous shale (HOSS), high organic-rich argillaceous shale (HOAS), medium organic-rich siliceous shale (MOSS), medium organic-rich argillaceous shale (MOAS), and low organic-rich shale (LOS). The type of organic matter in the studied samples is mainly Type I kerogen and Type II kerogen, predominantly Type II1 kerogen. The kerogen mostly lie within the mature zone in the study area. Various types of pores have been identified in the studied shale: intergranular pores, intragranular pores, intercrystalline pores, organic matter pores, and seams around organic matter. The pores are commonly nanoscale to micrometer in scale, with diameters ranging from 10 nm to several microns. The S1 content in shale is positively correlated with the macropore content, indicating that macropores in shale are the main effective oil storage spaces and are important for oil-bearing reservoirs. There is a good positive relationship between the macropore volume of shale and the content of organic matter. Organic matter in the shale can be beneficial for generating organic matter pores, dissolution pores, and seams at organic matter edge, resulting in better physical properties of shale reservoirs. There is a negative relationship between the quartz/feldspar content and macropores content, indicating that quartz and feldspar are detrimental for the macropore volume development. The lithofacies type is one of the important factors controlling the macropore volume. MOAS and HOAS are favorable lithofacies for the development of macropores. The findings of this study can be utilized for hydrocarbon exploration and development in the lacustrine shale formation of the Ordos Basin and other similar basins.

Clarifying the contribution of multiscale pores to physical properties of Chang 7 tight sandstones: insight from full-scale pore structure and fractal characteristics

The pore structure and its heterogeneity of tight reservoirs are key factors affecting the storage and percolation of crude oil. The pore system of Chang 7 tight sandstone has multi-scale and multi-type characteristics. However, the contribution of different pore types and pore sizes to the physical properties of Chang 7 tight sandstone is still unclear. In this paper, we collected a suite of Chang 7 tight sandstones to investigate the full-scale pore structure and fractal characteristics by casting thin section, field emission scanning electron microscope, two-dimensional multi-scale backscattered scanning electron microscopy, N2 adsorption (NA) and NMR. The pore diameters of Chang 7 tight sandstone are usually distributed between 0.001 and 20 μm. Intercrystalline pores are mainly distuibuted <500 nm. Dissolution pores vary from 100 nm to 100 μm. Residual intergranular pores range from 1 μm to 40 μm. Based on the fractal characteristics, pore system is divided into macropores (mainly >300 nm), mesopores (mainly 7–300 nm), and micropores (mainly <7 nm). Micropores are adsorb-fluid pores that do not contribute to the storage and percolation but contribute significantly to contrasting specific surface area. Mesopores represent bound-fluid pores and only contribute to total porosity but not to permeability. Macropores represent movable-fluid pores, contributing to both porosity and permeability. The content and heterogeneity of macropores control the quality of Chang 7 tight sandstone. When macropore volume is >12×10−3 mL/g, the continuous percolation network consists entirely of macropores, resulting in higher porosity and permeability of the reservoir. Moreover, reservoir physical properties show excellent correlation with macropore heterogeneity. These results demonstrate that the content and heterogeneity of macropores are key indicators indicating the quality of the Chang 7 tight sandstones.

Physicochemical characteristics of natural and anthropogenic inorganic and organic solid porous materials: Comprehensive view

Complex textural analyses and ultimate analyses of 23 inorganic and organic solid porous materials of natural and anthropogenic origin have been performed. The type of pores, porosity and pore size distributions are discussed. While Halloysite, Biocalith K and Diatomaceous earth have a balanced distribution of all pores, Clinoptilolite and Kemira have a high micropore content and Montmorillonite contain predominantly mesopores. SH-GC has the highest micro-mesopore content. Natural materials and materials prepared from raw materials have SBET values <50 m2/g, whereas materials on the basis of activated carbon and montmorillonite or pure granulated Fe(OH)3 have SBET > 50 m2/g. The highest porosity values correspond with an extremely high content of macropores in the Eco-Dry Compact and Eco-Dry Plus samples, and in the Wood sawdust samples, where at the same time the presence of the smallest pores is sporadic. The highest micropore values were observed in a sample from the category of aluminosilicates and in samples of activated carbon. Overall, the diverse variability of the properties of these solid porous unconventional materials was revealed, which offers the possibility of wide use for various types of adsorption, both in raw form and after appropriate material treatment. The material is discussed for the suitability of using to remove specific types of pollutants.

Mechanism of the pore and molecular structure evolution of coal exposed to acid mine drainage (AMD)

In the post-extraction epoch, wastewater from mining activities, particularly acid mine drainage (AMD) residing in sulfur-laden coal terrains, assumes a pivotal role in the safety stewardship of decommissioned coal mines. This research aims to investigate the mechanism behind coal characteristic deterioration from prolonged exposure to AMD. Immersion assays were performed on coal samples across pH 2 to 5 to assess the impact of acid mine drainage. Subsequently, the pore and molecular architecture was appraised using microscopic methodologies. Computed Tomography (CT) findings elucidate that post-immersion, the porosity, and fissures proliferated longitudinally along the coal strata, engendering a marked amplification in surface porosity contiguous to pre-existing pores. This escalation in surface porosity was further accentuated in correlation with the intensification of AMD acidity. Nuclear Magnetic Resonance (NMR) data indicated a marginal augmentation in the content of both micropores and macropores within a tepid AMD milieu. However, in a more virulent AMD context, the proportion of micropores diminished, whereas that of macropores and pore throat size (PTS) experienced an upswing, thereby transmuting adsorptive pores into permeable conduits and consequently enhancing coal permeability. Scanning Electron Microscopy (SEM) corroborated the NMR outcomes; as AMD acidity transitioned from mild to severe, the coal matrix manifested many erosive pores, matrix layer disintegration, and an expansion in cleat width. Therefore, the microscopic pore evolution can be succinctly encapsulated as follows: in a mild AMD environment, dissolution of minerals predominates, generating erosive pores, whereas, in a more acidic AMD milieu, the matrix undergoes partial contraction, thereby augmenting pore volume, enhancing permeability, and inducing structural degradation. Additionally, Fourier Transform Infrared Spectroscopy (FTIR) analysis substantiated that AMD compromised the pore architecture and catalyzed the disintegration of coal macromolecules into lower molecular weight constituents. Therefore, AMD degrades coal macromolecules into smaller compounds, heightening matrix layer porosity and impairing coal characteristics. This research yields vital insights for the security and efficient management of abandoned mine excavations.

Experimental study on the disintegration characteristics of undisturbed loess under rainfall-induced leaching

Loess is prone to collapse as the soil approaches saturation, leading to severe geological hazards. However, how the undisturbed loess microstructure evolves due to rainfall-induced leaching is poorly understood and a detailed assessment of the corresponding disintegration characteristics is lacking. In this study, we conducted a series of leaching and disintegration tests on undisturbed Q3 loess from Yan’an, China. Loess disintegration on a macroscopic level were characterized using a self-developed disintegration apparatus, and the relationship with influencing factors such as moisture content, temperature, and salinity were explored. At the microscopic scale, scanning electron microscopy (SEM) was performed to qualitatively probe the underlying mechanisms of loess disintegration under varied leaching conditions. The microstructure properties of the loess samples revealed in the SEM images were examined using Image-Pro Plus (IPP) software. A quantitative relationship between the microstructural parameters of the pores and particles with disintegration was established based on the grey correlation theory. The results show that the disintegration process of undisturbed loess under the action of leaching can be divided into three stages: soaking, softening, and collapsing. Compared with samples without leaching, the study demonstrates that leaching can facilitate the loess disintegration. Under otherwise similar conditions, loess disintegration ratio decreases with increasing moisture content and salinity, whereas it increases with water temperature. In addition, microstructural observation shows that the undisturbed loess microstructure changed from interlocking to overhead with increased leaching, inducing favorable conditions for loess disintegration. Moreover, grey correlation analysis shows that the particle size distribution and macropore content of undisturbed Q3 loess yields a satisfactory correlation with the loess disintegration ratio. In general, rainfall-induced leaching effect is conducive to the disintegration of loess by degrading its internal structure.

Regulation of the pore structure of carbon nanosheets based electrocatalyst for efficient polysulfides phase conversions

The practical applications of lithium-sulfur (Li-S) batteries are hampered by the sluggish redox kinetics and polysulfides shuttle in the cyclic process, which leads to a series of problems including the loss of active materials and poor cycling efficiency. In this paper, the pore structures of carbon nanosheets based electrocatalysts were precisely controlled by regulating the content of water-soluble KCl template. The relationship between pore structures and Li-S electrochemical behavior was studied, which demonstrates a key influence of pore structure in polysulfides phase conversions. In the liquid-sloid redox reaction of polysulfides, the micropores and small mesopores (d < 20 nm) exhibited little impact, while the mesopores (d > 20 nm) and macropores played a decisive role. As a typical exhibition, the nickel-embedded carbon nanosheets (Ni-CNS) with a high content of large mesopores and macropores can aid Li-S batteries in exhibiting stable cycling performance (760.1 mAh g−1 at 1 C after 300 cycles) and superior rate capacity (847.8 mAh g−1 at 2 C). Furthermore, even with high sulfur loading (8 mg cm−2) and low electrolyte (E/S is around 6 µL mg−1), the high area capacity of 7.7 mAh cm−2 at 0.05 C could be achieved. This work can provide a guideline for the design of the pore structure of carbon-based electrocatalysts toward high-efficiency sulfur species redox reactions, and afford a general, controllable, and simple approach to constructing high performance Li-S batteries.

Analysis of the pore structure characteristics of saline soil in the profile within the frozen depth

Soil pores play a critical role in the complex physical coupling process and are closely associated with the mechanism of soil salinization. This research used mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and laser particle size analysis on a soil profile about 230 cm deep in Qian'an, where soda saline–alkali soil is distributed and the deepest underground freezing depth is 180 cm. The material composition of the soil in active layer was identified, and the soil pores were classified as micropores (<0.04 μm), small pores (0.04–0.4 μm), mesopores (0.4–4 μm), and macropores (>4 μm). The soil deposited at a depth of 0 to 80 cm was affected by freeze–thaw cycles and dry–wet cycles, developing longitudinal cracks. During the rainy season, clay particles and salt were carried downward by rainfall, whereas at a depth of 30 to 80 cm, the exchangeable sodium ions and clay particles in the soil created a thick diffused layer and hindered rainfall infiltration, resulting in salt accumulation. The small pore diameter and low porosity of the soil in this depth range caused pores degradation, further exacerbating the salinization process. The soil deposited at a depth of 80 to 120 cm had low clay content, resulting in limited upward migration of unfrozen water during freezing periods. Upon thawing, the salt and fine clay particles moved upward with capillary water, leading to a lower salt content than the upper soil. Additionally, this depth range had a high content of macropores with a large average pore diameter. The soil deposited at a depth of 120 to 180 cm had high clay content, and during short freezing periods, salt migrated upwards with unfrozen water along poorly connected longitudinal cracks with limited clay particle migration. The macropore content was low, and the average pore diameter was small due to clay particles filling the pores. The salt content in this depth range was lower than in the upper soil. The pore structure characteristics of the saline soil in the active layer provide insights into salt deposition mechanisms, and this research offers data support from a pore-scale perspective for preventing the salinization process.

Novel 3D analysis of reduction behavior of single iron-oxide particle in CO-CO2 gas atmosphere

The production of steel, which is achieved by the reduction of iron ores mainly through indirect reduction reactions in a blast furnace, is gradually increasing worldwide. Because the reducing gas diffuses three-dimensionally, irregular particle shapes influence the reduction through differences in the diffusion length. The analysis of actual irregularly shaped iron-ore particles using existing models is difficult because they are primarily effective for 1D systems. Therefore, a novel reduction model based on the 3D diffusion equation that accommodates irregular particle shapes and 3D systems was developed in this study. The established model was validated by reproducing experimental conditions and comparing the quantified effective diffusivity and chemical reaction rate constant using the shrinking core model. In addition, the model was used to investigate the reducing behavior of an actual sintered-ore particle and the effects of particle sphericity and macro pore content. The sintered-ore particle had a higher reduction rate than that of a spherical equivalent with the same volume because sections of the surface with shorter diffusion lengths facilitated the gas diffusion. Additionally, the particle sphericity was determined to be inversely proportional to the reduction rate because the rate of gas diffusion into the particle depended on the diffusion length. With respect to porous particles, the gas was found to readily diffuse into the particles through pores, leading to a higher reduction rate for higher pore numbers. Overall, the gas diffusion was confirmed to drive the reduction reaction.

Characterization on Structure and Fractal of Shale Nanopore: A Case Study of Fengcheng Formation in Hashan Area, Junggar Basin, China

The Lower Permian Fengcheng Formation in Halaalate Mountain in the Junggar Basin has enormous potential for shale oil, while few investigations on quantifying pore structure heterogeneity have been conducted. Thus, total organic carbon (TOC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and low-temperature N2 adsorption tests were conducted on the shales collected from the HSX1 well in the Hashan region to disclose the microscopic pore structure and its heterogeneity. Results show that the selected shales mainly consist of quartz, plagioclase, calcite, and clay minerals. The primary pore types are intergranular pores in quartz and carbonate and intragranular pores in clays, while organic matter (OM) pores are rare. Typical types of H2 and mixed H2-H3 were observed. Type H3 shale pore size distributions (PSD) are unimodal, with a peak at about 70 nm, while Type H2-H3 shales are bimodal, with peaks at about 70 nm and 3 nm, respectively. Type H3 shales have lower D2 than Type H2-H3 shale, corresponding to weaker pore structure heterogeneity. Multifractal analyses indicate that macropores in Type H3 shales have stronger heterogeneity with large D10−D0 ranges, while minor D−10−D0 ranges mean weaker heterogeneity of micro- and mesopores, and so do Types H2-H3 shales. The higher the contents of plagioclase and clay minerals, the more heterogeneous the micro- and mesopores are; a larger content of quartz leads to more heterogeneous macropores. Specific surface area, micro-, and mesopores contents positively correlate to D2, while average pore diameter and macropores are on the contrary, thus the higher the content of micro- and mesopores and the specific surface area, the lower the content of macropores and average pore diameter, the more complex the microscopic pore structure of shale. Micro- and mesopores control the heterogeneity of shale pore development with a great correlation of D−10−D0 and D−10−D10, and D2 can effectively characterize the heterogeneity of a high porosity area with a strong correlation of D2 and D0−D10.

Analysis of the Effect of Pore Structure on the Mechanical Properties of Concrete Based on the Meso Numerical Model

In the research on the influence of pore structure on the macroscopic mechanical properties of concrete, the experimental method cannot realize the accurate control of the pore structure parameters, and the research based on the numerical simulation method is insufficient in the scientific simulation and parameterization of the complex pore structure. A new numerical concrete modeling method is proposed, which introduces the total porosity, pore gradation, pore size, and sub-porosity of each gradation segment to realize the accurate simulation and parameterization of the pore structure. Based on the control variable method, 25 concrete mesoscopic models with the same aggregate structure and different pore structures are established, and uniaxial tensile experiments are performed. The pore structure accelerates the process of damage expansion from the periphery to the center of the specimen and makes the damage inside the cement mortar more localized. There are obvious exponential function relationships of three pairs: total porosity and elastic modulus, PSSA and elastic modulus, and tensile strength and total porosity. There is an obvious quadratic polynomial function relationship between tensile strength and specific surface area. For specimens with the same aggregate structure and total porosity, the elastic modulus increases with the increase of the macropore content, and the tensile strength and elastic modulus are basically not affected by the average pore radius. The effect of pore space distribution and sub-porosity on peak strain is greater than that of total porosity, but no obvious regularity is shown. For pores with a radius in the range of 0.15–0.8 mm, the smaller the pores, the greater the effect of their porosity on the elastic modulus and tensile strength, and the less effect on the peak strain.

Effect of different ice contents on heat transfer and mechanical properties of concrete

With annually decreasing shallow mineral resources, development and utilization of deep mineral resources are critical. However, heat hazards in deep mines pose hidden dangers to health and safe operation of equipment. Therefore, a suitable cooling method is an urgent concern in deep high-temperature mines. This study proposes a cooling method that introduces ice into concrete for phase change cooling and improved strength characteristics. It can be used in deep high-temperature mines, and is known as iced-concrete technology. Based on temperature monitoring, mechanical strength tests, and microstructure tests, this study explores the influence of different ice contents (0 %, 10 %, 20 %, 30 %, 40 %, 50 %, 60 %) on heat transfer and mechanical properties of concrete, and analyzes the mechanism of heat transfer and the mechanical properties of concrete under the action of ice particles. The results show that: (1) the temperature evolution law of concrete with different ice contents takes 18 h–26 h and has a temperature change inflection point interval that first increases and then decreases. With an increase in ice content, the lower the initial temperature, the greater the rate of temperature change. (2) Ice particles have an obvious positive effect on the uniaxial compressive strength and splitting strength of concrete; the final mechanical properties of concrete are positively correlated with the ice content with a constant water (ice)–cement ratio. (3) Compared with ordinary concrete, the initial low-temperature water storage capacity of iced concrete promotes formation of hydration products in the later stage to some extent, improving the content of hydration products in the curing stage, promoting the full filling of internal concrete pores, reducing the content of harmful macropores and mesopores, optimizing the pore structure, and improving the compactness and mechanical strength of the concrete. (4) The cooling efficiency of concrete was increased with an increase in ice content. The cooling efficiency of concrete with 60 % ice content was six times that of ordinary concrete. When the ice content exceeded 20 %, the cooling capacity generated by ice–water phase change was greater than the heat absorbed by the temperature change of the water.

Mechanism Analysis of the Influence of Freeze-Thaw on the Damage and Debonding Evolution of Sandstone-Concrete Interface

During tunnel construction in cold regions, the good adhesion of surrounding rock-lining interface is one of the important preconditions to evaluate the durability of tunnel lining. However, the repeated fatigue damage between rock and concrete due to the freeze-thaw action leads to debonding at the interface, which significantly affects the protective effect of shotcrete. Accordingly, based on the combination of sandstone-concrete as the object, through the development of sandstone-concrete interface freeze-thaw cycling test, and combining the nuclear magnetic resonance (NMR) test and scanning electron microscopy (SEM) analysis, the mechanism of debonding by freeze-thaw damage at the sandstone-concrete interface was systematically revealed. The conclusions drawn are as follows: (1) With the increase of freeze-thaw times, the content of micropores and macropores at the interface gradually increases, while the content of mesoporous gradually decreases. At the same time, the decrease of freeze-thaw temperature also aggravates the growth of interface cracks, and the freeze-thaw damage of interface is closely related to the minimum freeze-thaw temperature. (2) The damage of the sandstone side becomes more serious under multiple freeze-thaw actions. Concrete as a water retaining plate inhibits the migration of water to its interior, and a pot cover effect exists at the interface to provide better storage space for water accumulation. (3) The C-S-H group is the main source of the bond force of sandstone-concrete interface, and the freeze-thaw effect aggravates the fracture of the C-S-H group, which leads to the interface debonding. This study could provide an experimental basis and theoretical support for systematically recognizing the evolution mechanism of freeze-thaw damage and debonding of shotcrete in tunnels in cold regions.

Microscopic pore structure characteristics of tight limestone reservoirs: New insights from Section 1 of the Permian Maokou Formation, Southeastern Sichuan Basin, China

Recently, industrial gas flows have been produced from the vertical well acidification tests of Wells JS1 and YH1 in Section 1 of the Maokou Formation in the southern region of eastern Sichuan Province, China. This result proves that Section 1 contains a group of excellent source rocks and gas-bearing reservoirs. In this study, the pore structure characteristics and primary causes of the nanopore structure were explored using scanning electron microscopy, X-ray diffraction of total rocks, total organic carbon, liquid nitrogen adsorption, and other experimental methods to determine the pore development features of nodular limestone reservoirs in Section 1. The results substantiate the presence of complex pore structures in the nodular limestone reservoirs in Section 1. Nanopores are dominant and mainly comprise micropores and mesopores approximately 4 nm in diameter. The pore forms are particularly schistose clay silt pores consisting of rigid particles and flask-shaped pores. N 2 adsorption analysis showed that the specific surface area of the carbonate reservoir was 4.8842–8.1594 m 2 /g (mean = 6.0439 m 2 /g), and the pore volume was 0.008422–0.015098 cm 3 /g (mean = 0.043212 cm 3 /g). Mesopores were positively related to the total pore volume and total specific surface area, whereas macropore content had poorer correlations. Mesopores contribute more to the total pore volume and total specific surface area than macropores do. Spaces among the clay mineral layers (especially talcum gaps) predominantly contributed to the carbonate pore volume and specific surface area of the reservoir, and were positively related to the clay mineral content. The rocks have highly developed calcite pores, and their pore volumes and specific surface areas are negatively related to calcite pore content. Moreover, low organic content and low pore development degrees were observed. The organic content was weakly correlated with the pore volume and specific surface area, suggesting a low effect on reservoir performance. This assessment of the pore structure characteristics of Section 1 of the Maokou Formation yielded essential geological data that could inform the formulation of exploitation measures. • Identify the pore development features of nodular limestone reservoirs in Section 1 of the Permian Maokou Formation. • Explore the main factors that influence the pore structure. • Discussion on the relationship between pore structure and oil and gas resources.

Self-shrinking Ailanthus altissima substrate obtained by ultrasonic-assisted treatment: Density and pore structure characteristics

The pore structure characteristics of wood are important factors affecting permeability. The main objective of this study was to evaluate the density and pore structure characteristics of self-shrinking Ailanthus altissima substrate obtained by ultrasonic-assisted treatment. In the experiment, 320 W and 25 kHz ultrasound combined with alkali solution (1%, 4% and 8% NaOH) was applied. The pore structure, chemical groups, macroscopic and microscopic morphology of samples were investigated by mercury intrusion porosimetry, Fourier transform infrared spectroscopy, stereomicroscopy, and scanning electron microscopy. The results indicated the cell-wall components (particularly hemicelluloses) were degraded or transformed. Thus, the density (oven-dried, skeletal and bulk) and pore structure of the wood were altered. In the condition of 1% and 4% NaOH condition, a uniform self-shrinking wood block with relatively-high oven-dried density and bulk density, but lower porosity than the water-immersion samples, was obtained by ultrasonic-assisted treatment. In comparison with the water-immersion samples, the distribution of pores of samples in alkali condition shifted towards larger diameters, particularly ultrasonic-assisted one. The relative content of macropores (> 0.5 µm) increased, and the relative content of ultrasonic-1% NaOH-treated samples reached 86.10%.

Process Chain Development for the Fabrication of Three-Dimensional Braided Oxide Ceramic Matrix Composites.

Fiber composites with a three-dimensional braided reinforcement architecture have higher fiber volume content and Z-fiber content compared to a two-dimensional braided reinforcement architecture; as a result, the shear strength increases. Porous oxide fiber composites (OFCs) have the inherent weakness of a low interlaminar shear strength, which can be specifically increased by the use of a three-dimensional fiber reinforcement. In this work, the braiding process chain for processing highly brittle oxide ceramic fibers is modified; as a consequence, a bobbin, which protects the filament, is developed and quantitatively evaluated on a test rig with regard to tension and filament breakage. Subsequently, a braiding process is designed which takes into account fiber-protecting aspects, and a three-dimensional reinforced demonstrator is produced and tested. After impregnation with an Al2O3-ZrO2 slurry, by either a prepreg process or a vacuum-assisted process, as well as subsequent sintering, the three-dimensional braid-reinforced OFC exhibits an interlaminar shear strength (ILSS) which is higher than that of two-dimensional braid- or fabric-reinforced samples by 64–95%. The influence of the manufacturing process on the relative macropore content is investigated and correlated with the mechanical properties.

Pore Structure Characteristics of Tight Carbonate Reservoir in Qingxi Sag, Jiuquan Basin

Abstract The Xiagou Formation is the main tight oil reservoir in Qingxi Sag of Jiuquan Basin. Given the poor physical properties and other factors restricting tight oil exploitation and production in this area, studies should focus on microscopic pore structure characteristics. In this study, a nano-CT scanner, a SEM, and an NMR were used to study the pore structure characteristics of a tight carbonate reservoir in Qingxi Sag, Jiuquan Basin. The Xiagou Formation reservoir mainly consists of gray argillaceous dolomite and dolomitic mudstone. The pore categories are mainly elliptic, irregular, intergranular, and intragranular and mostly filled with clay and carbonate cement. Pore space is small, the intergranular or organic pores are mostly separated, and pore-throat is weakly connected. The throats mostly develop with lamellar and tube bundle-like characteristics and with poor seepage ability. The pore-throats mostly span from nanometer to micrometer sizes, and pore diameters are mainly concentrated in the range of 0.01–0.1 and 1–10 μm. It is a unimodal pattern mainly composed of micropores, or a bimodal regular allocation dominated by micropores supplemented by macropores. The relationship between micropore (&amp;lt;0.1 μm) and macropore (&amp;gt;1 μm) content allocation and mean pore diameter strongly controls the permeability of reservoir rocks. When macropore content reaches more than 85%, or when pore content totals less than 3%, the permeability of a reservoir remarkably increases. At a higher ratio of the average finest throat sectional area and throat-pore of reservoir rock, the throat radius lies closer to the connecting pore radius, pore and throat connectivity improves, and reservoir seepage ability becomes stronger. Based on reservoir capacity and seepage ability, pore structures of the tight carbonate reservoirs in study area are classified into type I (small-pore–thin-throat), type II (thin-pore–thin-throat), and type III (microporous-microthroat) with rock permeability&amp;gt;0.1 mD, 0.05–0.1 mD, and &amp;lt;0.05 mD, respectively. The type I pore structure reservoir should be regarded as an indicator of tight oil “sweet spots” reservoir in the study area.

Highly performed nitrogen-doped porous carbon electrocatalyst for oxygen reduction reaction prepared by a simple and slight regulation in hydrolyzing process of ZIF-8

A simple and environmentally friendly method to prepare nitrogen-doped porous carbon (NPC) electrocatalysts for oxygen reduction reaction (ORR) is studied by using glucose (Glu) to regulate the hydrolyzing process and structure of ZIF-8 precursor. Compared with pristine ZIF-8, the ZIF-8 regulated by Glu (Glu/ZIF-8) has smaller particle size. NPC has a higher content of mesopores and macropores, a higher degree of graphitization, and a higher content of pyridine and graphitic nitrogen than nitrogen-doped carbon (CN) derived from prisitine ZIF-8. The onset potential, half-wave potential, and limiting current of NPC for ORR in 0.1 ​M KOH medium is 0.99 ​V, 0.88 ​V, and 5.43 ​mA ​cm−2, respectively. The electrocatalytic performance of NPC is similar to Pt/C, and better than CN. Furthermore, its stability and resistance to methanol are better than Pt/C. Its high electrocatalytic performance is attributed to the effect of Glu on the structure of ZIF-8 precursor.