Pore Structure Characteristics Research Articles

A Novel Porous Diffusion Model during Gas Desorption in Coal Based on Fractal Characteristics of Pore Structure

A Novel Porous Diffusion Model during Gas Desorption in Coal Based on Fractal Characteristics of Pore Structure

Study on the Cross-Scale Effects of Microscopic Interactions and Mechanical Properties of Rigid Polyurethane Foam Driven by Negative-Temperature Environments

In order to investigate the cross-scale effects of the interaction between the hard and soft segments of stiff polyurethane foam on the material’s mesoscopic pore structure and macroscopic compression characteristics in various negative-temperature environments, this paper used molecular dynamics to calculate the interaction differences between hard and soft segments in different negative-temperature environments. The effects of various negative-temperature settings on the cell structure of stiff polyurethane foam were investigated using scanning electron microscopy and Image J software. Finally, macro experiments were used to determine the influence of a negative-temperature environment on the characteristics of stiff polyurethane foam (such as compressibility). The molecular simulation calculation results show that in a negative-temperature environment, decreasing temperature gradually increases the interaction between hard segment molecules and soft segment molecules, resulting in an increase in the molecules’ modulus and cohesive energy density. The scanning electron microscope results reveal that a negative-temperature environment gradually increases the pore diameter of stiff polyurethane foam. The compression experiment findings demonstrate that, for the same service duration, the compressive strength in the −20 °C environment is 27.53% higher than that in the 0 °C environment. The study’s findings reveal a microscopic mechanism for the following receiving alterations and toughness enhancement of rigid polyurethane foam throughout service in negative-temperature conditions.

Study on Sensitivity Mechanism of Low-Permeability Sandstone Reservoir in Huilu Area of Pearl River Mouth Basin

Reservoir sensitivity is a parameter that is used to evaluate the degree of change in reservoir permeability under the influence of external fluids. Accurate evaluation of reservoir sensitivity is conducive to the optimization of fluid parameters during exploration and development. Taking the Wenchang Formation and Enping Formation of the Paleogene in the Huilu area of the Pearl River Mouth Basin as the research object, reservoir sensitivity experiments were carried out. Combined with the corresponding experimental results obtained using methods such as thin section identification, scanning electron microscopy (SEM), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and screening analysis, based on mineral sensitization and pore structure sensitization, qualitative and quantitative evaluations of reservoir sensitivity were carried out, and factors affecting sensitivity and sensitization mechanisms were analyzed. This work shows the following: (1) The sandstone reservoirs in the two areas have the same clay type, but the total clay content of the Wenchang Formation is greater than that of the Enping Formation. The porosity of the Wenchang Formation is less developed than the Enping Formation. (2) The Wenchang Formation has weak or moderately weak water sensitivity and moderately weak or moderately strong flow velocity sensitivity. The water sensitivity of the Enping Group samples is moderately weak or moderately strong, the flow rate sensitivity is moderately weak, the alkali sensitivity is weak, the acid sensitivity is moderately weak, and the salinity sensitivity is moderately weak or moderately strong. (3) The sensitivity of the Wenchang Formation is mainly affected by the content of clay minerals. The sensitivity of the Enping Formation is also affected by the clay content and type. Although the clay content is not high, the permeability is more susceptible to sensitivity due to the pore structure and debris particle distribution characteristics. These conclusions are beneficial for the selection of fluid parameters and efficient reservoir development.

Influence of crack and pore structure characteristics on the thermal protective performance of thermal barrier coatings based on LBM

Influence of crack and pore structure characteristics on the thermal protective performance of thermal barrier coatings based on LBM

Characterization of Pore Structure and Water-Driven Residual Oil Distribution in Low-Permeability Reservoirs Based on Digital Cores

Characterization of Pore Structure and Water-Driven Residual Oil Distribution in Low-Permeability Reservoirs Based on Digital Cores

Do Pores Exist?—Foundational Issues in Pore Structural Characterisation

This work reviews a range of fundamental theoretical considerations in pore structural characterisation. The pore concept is essential for providing a better understanding of physical processes arising within porous media than purely phenomenological approaches. The notion of a pore structure is found to be independently valid and invariant during theory change concerning said physical processes, even for structural models obtained via indirect methods. While imaging methods provide a more direct characterisation of porous solids, there is often a surfeit of information beyond that which can be wielded with current computing power to predict processes sufficiently accurately. Unfortunately, the pore network model extraction methods cannot decide in advance the level of simplification necessary to obtain the optimum minimal idealisation for a given physical process. Pore network models can be obtained with differing geometrical and topological properties, but similar mass transfer rates, for reasons that are often not clear. In contrast, the ‘pore-sifting’ strategy aims to explicitly identify the key feature of the void space that controls a mass transport process of interest.

Study on the mechanism of methane “solid–liquid–gas” conversion controlled by the evolution of coal micro- and nanopore structure

Currently, the utilization of coalbed methane resources in the Guizhou region faces challenges such as complex reservoir structure, high gas content, and microporous development. Based on these, the pore structure and adsorption capacity of Guizhou tectonic deformed coals (TDCs) were evaluated using a suite of integrated diagnostic techniques including low-temperature nitrogen adsorption (LT-N2A), mercury intrusion porosimetry (MIP), methane isothermal adsorption. Through the above methods, the pore structure and adsorption characteristics of the samples were characterized; The samples were divided into the range of joint pores by combining the results of MIP and LT-N2A; Using the molecular simulation software, the 2 nm, 4 nm, 10 nm pores affecting the methane endowment state were investigated respectively, and from the perspective of the heat of adsorption and energy, the concept of the three-phase transition of methane was proposed, and explore the change of the pore spacing affecting the endowment state of methane from the solid state pore to the gas state pore. The results provide new ideas for the in-depth study of gas storage in tectonic coal reservoirs in Guizhou Province.

Quantitative characterization of 3D pore structures and percolation characteristics in bioturbated reservoir media based on X-ray micro-CT: a case study of the Neogene Sanya Formation in the Qiongdongnan Basin, Northern South China Sea

Organisms alter the primary texture of sediments, leading to alteration in petrophysical properties mediated by a textural and mineralogical contrast between burrow-fill and sediment host, which affects reservoir properties and fluid flow characteristics. In this article, in order to understand the microscopic pore structure and flow state of fluids in microscopic pores of bioturbated reservoirs, Ophiomorpha-bearing bioturbated reservoirs in the Neogene Sanya Formation of the Qiongdongnan Basin in the northern South China Sea were selected to research. Micro-CT was applied to scan selected core plugs, and a 3D pore structure model was established. The geometric characteristics of the microscopic pore structure were quantitatively and visually characterized by a modified maximal ball algorithm, and connectivity analysis of the pore structure was carried out. Numerical simulations of the percolation characteristics of the analyzed bioturbated reservoir samples were performed using digital core software (Avizo) and multi-physics field simulation software (Comsol). The results show that: (1) 3D pore structures reveal that pore volume, pore area, pore equivalent radius, throat area, throat equivalent radius and throat length have a large distribution range; among them, the pore volume has the largest distribution range, which can vary by six orders of magnitude, indicating that the pore size distribution of the bioturbated reservoir is uneven and has strong heterogeneous characteristics; (2) the connected pore structure is very complex, and as the equivalent radius of connected pore increases, the coordination number also gradually increases, the better the connectivity. Numerical percolation simulation results also suggested that larger connected pore space plays a key role in the effective permeability of the reservoir. This study has important implications for analyzing the modification effect of bioturbation on oil and gas reservoirs, and enhancing production and recovery in the study area.

Preparation of tomato peel pomace powder/polylactic acid foams under supercritical CO2 conditions: Improvements in cell structure and foaming behavior.

Polylactic acid (PLA) is an eco-friendly material that can help address the problems of petroleum depletion and pollution. Blending renewable biomass materials with PLA to create composite foams with a tunable pore structure, superior performance, and low cost is a green technique for improving the pore structure and mechanical characteristics of single PLA foams. PLA/TP composites were created using melted tomato peel pomace powder (TP), which has a lamellar structure, as a reinforcing agent. Then, the relationship between the vesicle structure, morphology, and properties of the PLA/TP composite foams produced through supercritical CO2 intermittent foaming were investigated. The findings revealed that TP considerably enhanced the rheological characteristics and crystalline behavior of PLA. The PLA/TP composite foam had a better cell structure, compression characteristics, and wettability than pure PLA. The expansion ratio of the PLA/TP composite could reach 18.8, and its thermal conductivity decreased from 174.2 mW/m·K at 100 °C to 57.8 mW/m·K at 120 °C. Furthermore, annealing before foaming decreased the average composite foam blister size from 110.09 to 66.53 μm, and the annealing process also improved compression performance. This study contributes to solving environmental difficulties and creating PLA foams with controlled bubble structures, uniform bubble sizes, and outstanding overall performance.

Influence of IDS and SDS compound ratio on pore structure and wettability of bituminous coal and anthracite: Experimental and simulation discussion

The pore and wetting characteristics of bituminous coal and anthracite treated with different proportions of tetrasodium iminodisuccinate (IDS) and sodium dodecyl sulfate (SDS) were measured. The pore structure characteristics of the coal were studied via low-temperature nitrogen adsorption analysis and the Frenkel-Halsey-Hill fractal theory. Zeta potential measurements were conducted to quantitatively analyze the degree of aggregation or dispersion of coal particles dissolved in solution. Changes in the coal surface morphology were observed and analyzed by scanning electron microscopy (SEM). The results show that when the ratio of IDS:SDS is 1:3, the specific surface area (SSA) values of bituminous coal and anthracite are the lowest. The composite reagent has a greater effect on improving the pore structure of anthracite than bituminous coal. Compared with bituminous coal, anthracite has better pore connectivity and a wider pore network. The absolute zeta potentials of bituminous coal and anthracite reach the maximum at an IDS:SDS ratio of 1:3, with values of 91.08 mV and 91.35 mV, respectively. The electrostatic potential distributions of the molecules show that the advantages of the electrostatic potential difference with water molecules enable IDS and SDS molecules to effectively attract water molecules and form hydrogen bonds, thus revealing the optimization mechanism of coal wettability.

Amine-impregnated natural inorganic nanotubes via layer-by-layer electrostatically self-assembly approach for efficient CO2 adsorption

Developing cost-effective and high-performance solid amine adsorbents has considered as an important way to alleviate the greenhouse effect. How to precisely regulate its pore structure and surface interface characteristics, and how to cooperate to optimize the dynamic mass transfer and adsorption–desorption behavior of gas in the adsorbent are still challenging work. Herein, we demonstrated a facile and efficient approach to construct polyethyleneimine (PEI) impregnated halloysite nanotubes (HNTs) as an emerging nanocomposite for CO2 capture. Based on the natural electrostatic differences of inner and outer walls for HNTs, the hollow tubular structures of adsorbents were constructed by selective surface modification and layer-by-layer electrostatic self-assembly technology to improve the CO2 uptake capacity and cyclic stability, in which poly(sodium-p-styrene sulfonate) (PSS) and PEI were used as polyanionic and polycationic layer, respectively, to coat the inner walls of HNTs. The loading capacity of PSS-PEI composite ionic layers in HNTs and the influence of PSS polyanionic layer on PEI dispersion were specifically discussed according to the CO2 uptake capacity, adsorption heat, thermodynamics and kinetics of the adsorbents. The optimal PEI20-0.5PHNTs adsorbent exhibited a higher CO2 uptake of 0.87 mmol/g at 80 °C in the flow of 40 vol% N2/60 vol% CO2 than that of PEI20-HNTs, owing to the high amine efficiency due to the uniform dispersion of PEI in the electrostatic composite ionic layers. Furthermore, PEI20-0.5PHNTs reached 75 % of the maximum adsorption capacity at the 5th min of the adsorption process and released the most heat during adsorption at − 18.28 kJ/mol due to the presence of electrostatic composite ionic layers. PEI20-0.5PHNTs showed excellent cyclic stability with a slight loss of 7.4 %. The electrostatic self-assembled adsorbent obtained by layer-by-layer loading of PSS and PEI based on the unique surface charge characteristics of HNTs is an inspiration for the synthesis of cost-effective solid amine adsorbents for practical CO2 capture and separation.

Sustainable metal-organic framework based paper sheet as wallpaper for passive indoor moisture control

Passive indoor moisture control is a meaningful way to reduce HVAC operation and improve building energy efficiency. Metal-organic frameworks (MOFs) have been considered one of the most promising sorbent materials for passive indoor moisture control. However, the powder form of MOF is challenging to use in the built environment. Typical shaping methods like pellets, beads, and coating can lead to problems like partial pore blocking, insufficient mechanical stability, amorphization, and low material utilization. Here, we report a new sustainable MOF paper sheet comprising 25% cellulosic fibers and 75% MOF MIL-100(Fe) powder. The porous polymer matrix provides good support and fixation for MOF particles, so it’s more applicable in the built environment. The crystalline and pore structure characteristics of the MOF in the membrane are well preserved. Hydro characteristic test results show that MIL-100(Fe) paper sheet has high water vapor uptake, S-shape isotherm, mild regeneration condition, and high MBV. Then, a numerical model was developed to calculate the relation between a material’s MBV and its thickness. MIL-100(Fe) paper sheet with the most efficient thickness was applied as wallpaper in a building energy simulation model. The simulation result shows that the MIL-100(Fe) paper sheet is promising for passive indoor moisture control. It can remove about 45%-55% of the latent cooling load in most European climate types.

Construction of highly robust amino orange peel cellulose for Cu2+ adsorption study

ABSTRACT In this paper, a kind of cellulose aerogel (HRCNFs) with high mechanical robustness and durability was prepared by using orange peel cellulose and polyethylenimine, and it was used for high-efficiency adsorption of Cu (II). Fourier analysed the structure and morphology of HRCNFs transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and the pore structure characteristics of the materials were evaluated by BET. The adsorption capacity of HRCNFs as adsorbent to remove Cu (II) ions from aqueous solution was further studied. The maximum adsorption capacity was 167.21 mg/g. Adsorption is mainly a single-layer chemisorption process. Based on FTIR and BET analysis, the adsorption mechanism is the strong surface complexation of amino, carboxyl, and hydroxyl groups with Cu (II). Through many cycles, HRCNFs retain their integrity and high mechanical robustness. Therefore, the synthesised HRCNFs material can be considered a promising adsorbent for the removal of Cu (II) ions from polluted water bodies.

Characterization of pore structures after ASP flooding for post-EOR

With the global assistance of oil fields entering the stage of improving oil recovery, diversified composite flooding technology has become one of the key research targets. This article takes composite flooding to improve oil recovery as the research object, explores the differential mechanism of crude oil displacement efficiency under water flooding and composite flooding conditions, and elucidates the dynamic evolution characteristics of pore structure before and after composite flooding. Results show that: (a) The permeability and porosity of Daqing oilfield cores have a good correlation. The porosity of cores after water driving and ternary composite driving mainly ranged from 23.6 % to 27.4 % and 22.8 %–26.8 %. The water-driving permeability mainly ranged from 168 × 10−3 μm2 to 2162 × 10−3 μm2. Ternary composite driving permeability mainly ranges from 302 × 10−3 μm2 to 2307 × 10−3 μm2. (b) Compared with water driving, quartz and clay minerals are corroded by alkali during ternary composite driving. (c) Under the condition of similar permeability, the average pore size of the core after ternary composite driving is smaller than the average pore size after water driving.

Solid waste-based low-carbon autoclaved aerated concrete: Relationship between engineering properties and microstructure

A novel low-carbon autoclaved aerated concrete (AAC) was developed to enhance the high valuable use of solid waste in production, incorporating furnace slag, metro shield sand, and quartz tailings sand as 100 % siliceous raw materials, constituting 60 % of the total weight. In this study, comprehensive analyses were conducted on its engineering properties, including density, compressive, flexural, and splitting tensile strengths, and thermal conductivity. Advanced techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and high-resolution Industrial CT scanner (X-CT) were employed to examine AAC's material composition, hydration products, and pore structure characteristics at the microscale. The results indicated that the addition of 10 % furnace slag resulted in a specific increase of 5.5 % in compressive strength. However, escalating the furnace slag content to 30 % proved detrimental to the toughness and dry shrinkage of AAC. The microstructure analysis indicates that the use of furnace slag can improve the connectivity and roundness of pores and reduce the probability of large pores (>0.01 mm3), which will reduce the risk of damage localization. Furthermore, furnace slag in AAC enhanced sustainability and cost-effectiveness compared to metro shield sand and quartz tailings sand. Based on the TOPSIS model, an optimal AAC mixture, considering engineering performance, economy, and sustainability, was derived by blending the three types of solid wastes.

Pore structure characteristics of coral reef limestone: a combined polarizing microscope and CT scanning study

Coral reef limestone is a special class of geological medium formed through long-term deposition following the death of reef-building coral groups. Because it retains the skeletal structure of marine organisms during its formation, its pore structure is hyper-developed and complex. Deciphering the pore structure of the coral reef limestone is important because it is closely related to its macroscopic physical and mechanical properties. This study conducted a comprehensive analysis of the pore structure features of two types of coral reef limestone collected from the construction site of a nuclear power station located in the South China Sea using a combination of polarizing microscopy and CT scanning technologies. The fractal dimension of the pore structure of the treated reef limestone image was calculated, and the pore structure characteristics were statistically analyzed by considering several parameters including porosity, pore size, pore equivalent radius, shape factor, etc. In addition, the directional feature of the pore structure was explored. The results show that the improved watershed segmentation algorithm can accurately segment the pore structure of reef limestone images; both coral reef limestone specimens are loose of high porosity; the fractal dimension of pore structure lay between 1.58∼1.75, indicative of a high self-similarity; the pore size of the two coral reef limestone specimens is quite different, and the distribution of equivalent pore radius conforms to the normal distribution law; the pore structure of the two samples had obvious directionality, which can be quantified using a directional tensor. This study sheds light on future investigations linking the microscopic structure and macroscopic properties of coral reef limestones.

High-performance PVDF/PVB blend membranes with tailored sponge-like structure and antifouling properties for beer filtration

Currently limited research reported the design of microfiltration (MF) membranes specially for handling complex food processing streams such as rough beer. This study aimed to address this knowledge gap by tailoring for the first time a new class of polyvinylidene fluoride/poly(vinyl butyral) (PVDF/PVB) blend MF membrane with highly controllable pore structure and improved anti-fouling properties, and demonstrate its potential in real rough beer filtration. Combining an unconventional nonsolvent thermally induced phase separation (NTIPS) method and a unique quinary dope solution (i.e., PVDF/PVB/PVP/DMAc/MgCl2) with lower critical solution temperature (LCST) feature, the roles of PVB content and coagulation temperature were investigated in terms of pore structure characteristics and hydrophilicity. Although both the control PVDF membrane M0 without PVB and M6 with optimal 6.0 % PVB achieved similar turbidity removal (98–100 %), M6 exhibited enhanced permeance ranging from 27 % to 12 % with increasing simulated feed complexity from containing dextran only, yeast only to yeast/dextran mixture. The contribution of fouling of these key beer components was analyzed, indicating that the co-existence of yeast and dextran significantly aggravated fouling. Combining with membrane autopsy, in real rough beer filtration M6 showed permeance of 26.7 L·m−2·h−1·bar−1 at 1 bar that was ∼70 % higher than M0. Although with ∼50 % less irreversible fouling than M0, water cleaning implemented on M6 only recovered 62.5 % of flux. The simultaneous investigations on alkaline cleaning and operating pressure found that: a reasonably low pressure seemed favorable, e.g., 63.6 L·m−2·h−1·bar−1 at 0.2 bar, achieving up to flux recovery of ∼91 % with only ∼10 % contributed by irreversible fouling. Overall this study offers a facile yet practical strategy to tailor membranes for beer filtration, serving as an inspiration for designing future membrane processes for treating complex food processing and industry waste streams.

Optimization mechanism of metakaolin on micro-mechanical properties and pore characteristics of steel fiber-cement matrix interface

The study investigated the influence of aeolian sand and metakaolin(MK) on the micro-mechanical properties and pore structure characteristics of the interfacial transition zone(ITZ) between steel fibers and matrix in steel fiber-reinforced cement-based materials by nanoindentation, scanning electron microscopy(SEM) imaging, and energy-dispersive spectroscopy(EDS) analysis. The results demonstrated that including MK and aeolian sand led to a denser and uniform micro-structure in the ITZ, along with reducing the porosity and refining the pore size within there. Furthermore, MK could enhance the micromechanical properties of the C-(A)-S-H) gel by increasing the Al/Si ratio. Finally, the Copula function further confirmed the correlation between porosity(pore size >0.2μm) and micro-mechanical properties in the ITZ. This study provides a theoretical basis for the engineering application of aeolian sand and metakaolin, and proves the feasibility of porosity to characterize the microscopic mechanical properties of the interfacial transition zone of cement-based materials. Thus, it has specific engineering value and academic significance.

Multi-scale pore structure characteristics of coal under alternating hydraulic intrusion pressure

Multi-scale pore structure characteristics of coal under alternating hydraulic intrusion pressure

Evolution of pore structure and analysis of freeze damage in granite during cyclic freeze-thaw using NMR technique

Understanding the changes in a rock's pore structure and unfrozen water content during the freeze-thaw (F-T) process is crucial for unraveling the F-T damage mechanism of rock masses. This study employs nuclear magnetic resonance (NMR) tests to resolve the pore structure characteristics of granite specimens subjected to varying numbers of F-T cycles (0, 50, 100, and 200 cycles). Throughout the F-T process, unfrozen water (comprising bound water and free water) is quantified through T2 distribution curves, and the freeze-induced strain at different subzero temperatures is investigated. The results reveal that F-T cycles lead to the expansion of pore sizes from small to large, reducing the complexity of the pore structure. Moreover, an increased proportion of meso- and macro-pores accelerates the rate of water-ice phase transition in granite specimens, resulting in intensified freeze damage and greater maximum freeze-induced strain. Additionally, when previously damaged granite is refrozen, the presence of free water induces higher levels of freeze-induced strain. This research comprehensively analyzes the F-T damage process in granite, laying a crucial theoretical foundation for understanding freeze damage mechanisms in rock engineering.