Pore Structure Analysis Research Articles

Pore Structure and Fractal Analysis of Low-Resistivity Longmaxi Shale in the Southern Sichuan Basin Combining SEM, Gas Adsorption, and NMR

Pore Structure and Fractal Analysis of Low-Resistivity Longmaxi Shale in the Southern Sichuan Basin Combining SEM, Gas Adsorption, and NMR

Study on in-situ measurement and analysis method of rock pores based on borehole camera technology

In-situ measurement and analysis of pores are helpful to understand the properties of rocks. However, continuous quantitative analysis of pores in whole borehole is still difficult. Borehole camera technology can capture the borehole wall image of the whole well section by going deep into the borehole, which provides technical conditions for the measurement and analysis of pores. In this paper, a continuous measurement method of rock pores based on borehole camera technology is introduced. According to the characteristics of the optical image of borehole wall, a method of pore recognition and analysis is proposed. Specifically, the influence of redundant information on pore recognition is eliminated, and then the pores are accurately recognized by binarization and morphological operation. Based on the results of pore recognition and the coordinate information provided by borehole wall image, the calculation methods of surface porosity and line porosity are proposed, and the statistical analysis of pore distribution is realized according to the calculation results. In addition, the morphological characteristics of pores are also discussed. This method realizes the accurate recognition and quantitative calculation of pore structure based on borehole wall image, and provides a new method for continuous analysis of pore structure in the whole well.

Optimizing engineering potential in sustainable structural concrete brick utilizing pond ash and unwashed recycled glass sand integration

The Australian construction sector faces a dual challenge of high demand for concrete bricks and the need for sustainable materials. This research investigates eco-friendly structural concrete brick formulations, incorporating pond ash and unwashed recycled glass sand. It aims to provide scientific evidence on their engineering performance as per AS/NZS 4455.1:2008 standard, thermal insulation, and fire resistance properties. Additionally, microstructural, chemical, and pore-structure analyses are carried out to gain insights into the reaction mechanisms and the evolution of their properties. Findings indicate that bricks with 15% pond ash and 20% unwashed glass sand meet structural requirements with compression strength of 29.63MPa at 28 days. Enhanced thermal insulation is observed due to the lower densities of pond ash and glass sand. After a 2-hour exposure to elevated temperatures, the unexposed surface of these bricks remains below 180°C, satisfying fire resistance criteria for wall elements. However, microstructure and chemistry analyses suggest lower compression and tensile strength comparable conventional bricks because of low reactivity of the pond ash and the smooth surface of the glass sand.

Synthesis, characterization, and application of novel fluorescent sporopollenin for effective detection of mercury (II) ions from aqueous media.

In this investigation, a novel environmentally friendly functionalized fluorescent Sp-TAB hybrid material was advanced for the sensitive detection of environmentally polluting Hg(II). The characterization of the synthesized fluorescent Sp-TAB hybrid material using SEM and EDX provided insights into morphological and structural changes in the material's pore structure, while XRD and FT-IR analyses revealed the impact of the prepared material at each stage. Optimal parameters such as temperature, contact time, and pH influencing Hg(II) ion detection were determined. Application of the fluorescent Sp-TAB hybrid material was determined a detection limit (LOD) of 4.87μM for Hg(II) ions. This study shows the potential of the immobilization-enhanced fluorescent Sp-TAB hybrid material for sensitive Hg(II) ion detection in tap water. Additionally, this study is believed to serve as a model for sensitive and practical detection applications of heavy metals in the future.

Modification of the polymeric admixture based on polycarboxylate ether using silica-derived secondary materials obtained from fly ash and the efficiency of its application in concrete

The rising energy prices and the costs of CO2 emissions into the atmosphere are forcing the construction industry to search for ways to reduce cement consumption in concrete technology by optimizing concrete mixtures and making greater use of chemical admixtures. The scientific problem lies in understanding how polymers modified with silica-derived secondary materials, such as those obtained from fly ash (e.g., synthetic zeolites, mesoporous silica), interact with the concrete matrix and influence their durability and strength. The present study investigated the effect of a polymeric admixture based on polycarboxylic ether (PCE) modified with silica-derived secondary materials obtained from fly ash (synthetic zeolites, mesoporous silica) on the physical and mechanical properties of concrete. The study considered the effect of the modified polymer admixture dosed in 3 different amounts (0.4%, 0.8% and 1.2%) by weight of cement on the fresh properties of the concrete mixture, i.e. consistency and air content. The research scope also included determining the physico-mechanical properties of the concretes and investigating the effect of the modified admixture on the frost durability of the cement composite. In order to study the modification of the concrete microstructure, XRD phase analysis and air pore structure analysis by MIP were carried out. The study showed an increase in compressive strength after 28 days of curing in concretes containing the modified polymer of about 8-12% compared to the reference concrete. In addition, it was observed that strength increased with increasing admixture dosage. The resulting pore structure, contributed to improving the frost resistance of the concretes by reducing compressive strength loss from about 14% in reference concretes to about 2-9% in concretes with the modified polymer after 150 cycles of alternating freeze-thaw. At the same time, it was observed that the use of the modified polymer resulted in an increase in weight absorption from 2% do 4.5%, a more than twofold increase in depth of penetration of water under pressure and a more than 70% increased total porosity. In conclusion, the polymer-modified MCM-41 can positively affect the mechanical and durability properties of concrete, but it causes a change in the pore structure, which could have a negative effect on water absorption and total porosity.

Synergistic effect of nickel and graphite powders on the thermoelectric properties of ultra-high-performance concrete containing steel fibers and MWCNTs

The study investigates the influence of multi-walled carbon nanotubes (MWCNTs) and conductive powders, namely nickel powder (NP) and graphite powder (GP), on the mechanical and thermoelectric properties of ultra-high-performance concrete (UHPC). Flowability tests indicate that the addition of MWCNTs and conductive powders affects the flow diameter, with higher concentrations resulting in decreased flowability. Thermalgravimetric analysis and Fourier transform infrared spectroscopy reveal that the enhancement of the hydration reaction by 0.1 % MWCNTs in UHPC reaches saturation at this concentration. Pore structure analysis demonstrates a reduction in porosity and a denser structure upon the addition of 0.1 % MWCNTs. Mechanical tests indicate that the incorporation of 0.1 % MWCNTs enhances compressive and tensile strengths, whereas the introduction of 0.3 % MWCNTs diminishes the mechanical performance. Moreover, the electrical conductivity and thermoelectric effect are enhanced with the addition of MWCNTs and conductive powders. However, a decline in thermoelectric effect is observed when 0.3 % MWCNTs are added, although the conductivity remained high. The optimal thermoelectric performance is achieved with the combination of 0.3 % MWCNTs and 5 % NP, yielding a maximum power factor (PF) of 2148.2 μW/m·K2 and a figure of merit (ZT) of 4.9 × 10⁻7.

Fabrication and application of highly permeable ceramic membranes: Membrane-forming mechanism, pore structure, separation performance and fouling mechanism analyses

High separation efficiency and satisfactory economic benefits are of great importance for ceramic membranes in the field of water treatment. Herein, microfiltration ceramic membrane with high permeability and selectivity was prepared in one-step (dip-coating and sintering) by sacrificial-interlayer method. The membrane-forming mechanism, effect of temperature on the morphology and pore structure, separation performance, fouling mechanism, and regeneration performance of the ceramic membranes were systematically investigated. The results show that membrane-forming mechanism of the membranes largely depends on film-coating filtration. The membrane with a mixture of nanocellulose crystals and graphene oxide as sacrificial interlayer (C1G1) and sintered at 1100–1300 °C possessed smooth surface. The open porosity and average pore size increased, and the pore size distribution became broader as the temperature increased. Moreover, the sacrificial-interlayer membrane sintered at 1300 °C (mA4S-C1G1) possessed suitable porosity (53.4%) and average pore size (200 nm), high permeance (4828 L·m−2·h−1·bar−1), which was larger than that of the membrane without sacrificial interlayer, manifesting that C1G1 could prevent the penetration of membrane-forming particles into support. The final fouling mechanism of mA4S-C1G1 was cake filtration, although complete pore blocking, standard pore blocking, intermediate pore blocking also involved in the initial stage. In addition, the oil rejection rate (∼97%) and steady-state feed flux (810–1154 L·m−2·h−1) of mA4S-C1G1 was high, and it also possessed good regeneration performance.

Influence of CO2 curing on mechanical properties and microstructure of hydrated magnesium silicate

Hydrated magnesium silicate (M-S-H) samples with good fluidity of 270 mm were prepared. The mechanical properties of the M-S-H samples cured in CO2 conditions were examined. Moreover, the M-S-H samples under 70 % RH wet curing and standard curing conditions were prepared as comparison samples. As a result, the mechanical properties of the M-S-H samples under CO2 curing conditions significantly improved. Compared to the M-S-H samples under 70 % RH wet curing and standard curing conditions, the 28-day compressive strength of the samples under CO2 curing conditions was increased by 116.83 % and 74.25 %, respectively. Additionally, the microstructure of the M-S-H samples under the three curing conditions was investigated using XRD, SEM-EDS, TG/DSC, FTIR, and pore structure analysis. The results revealed that brucite reacted with CO2 to form nesquehornite under CO2 curing conditions. Furthermore, the volume stability of M-S-H was greatly affected by humidity, exhibiting expansion under standard curing and strong shrinkage under 70 % RH wet curing, while CO2 curing can attenuate the shrinkage of the M-S-H samples.

Role of modified calcium montmorillonite and 5 A zeolite in microstructure and efflorescence formation of metakaolin-based geopolymer

To reduce the efflorescence extent of metakaolin (MK)-based geopolymer, this study introduced thermally activated modified calcium montmorillonite (MT) and 5 A zeolite (ZT) into MK-based geopolymer, and the optimal mixing ratio was acquired by response surface methodology. The effect of the two modified clay minerals on the microstructural and mechanical properties of the MT-ZT-MK geopolymer was explored by compressive strength testing, phase analysis (XRD and FTIR), pore structure analysis (MIP), and morphology analysis (SEM-EDS). To investigate the performance and mechanism of efflorescence inhibition of the ternary geopolymer, the cation concentration in the leaching solution was detected by inductively coupled plasma atomic emission spectrometry (ICP-OES), and the efflorescence area of the geopolymer was calculated using Image Pro Plus (IPP) software. The results of the experiment showed that the optimal mixing ratio, as determined by RSM, was 1.5 wt% of modified MT and 2.9 wt% of modified ZT, with the highest compressive strength at 65.1 MPa and the lowest degree of efflorescence after 28 days of curing. It can be concluded that the two clays gradually exhibit the effect of cation exchange and internal curing. The pore structure is optimized and (N, C)-A-S-H gels are formed with the extension of curing time. On the other hand, the lesser extent of efflorescence possibly is attributed to the restricted channels for Na+ in the matrix to undergo carbonation with CO2 in the air.

Super-resolution reconstruction of hydrate-bearing CT images for microscopic detection of pore

The pore structure of marine natural gas-hydrate-bearing sediments is a key factor related to the physical properties of reservoirs. However, the resolution of micro-computed tomography (micro-CT) images is unsuitable for the analysis of pore structures in fine-grained sediments. In this regard, super-resolution (SR) reconstruction technology is expected to improve the spatial resolution of micro-CT images. We present a self-supervised learning method that does not require high-resolution datasets as input images to complete the training and reconstruction processes. This method is an end-to-end network consisting of two subnetworks: an SR network and a downscaling network. We trained on a self-built dataset of hydrate samples from three different particle sizes. Compared with typical methods, the SR results indicate that our method provides high resolution while improving clarity. In addition, it has the highest consistency with the liquid saturation method with the subsequent calculation of porosity parameters. This study contributes to the investigation of seepage and energy transfer in sediments containing natural gas hydrates, which is particularly important for the exploration and development of marine natural gas hydrate resources.

Image-based quantitative probing of 3D heterogeneous pore structure in CBM reservoir and permeability estimation with pore network modeling

Coalbed methane (CBM) recovery is attracting global attention due to its huge reserve and low carbon burning benefits for the environment. Fully understanding the complex structure of coal and its transport properties is crucial for CBM development. This study describes the implementation of mercury intrusion and μ-CT techniques for quantitative analysis of 3D pore structure in two anthracite coals. It shows that the porosity is 7.04%–8.47% and 10.88%–12.11%, and the pore connectivity is 0.5422–0.6852 and 0.7948–0.9186 for coal samples 1 and 2, respectively. The fractal dimension and pore geometric tortuosity were calculated based on the data obtained from 3D pore structure. The results show that the pore structure of sample 2 is more complex and developed, with lower tortuosity, indicating the higher fluid deliverability of pore system in sample 2. The tortuosity in three-direction is significantly different, indicating that the pore structure of the studied coals has significant anisotropy. The equivalent pore network model (PNM) was extracted, and the anisotropic permeability was estimated by PNM gas flow simulation. The results show that the anisotropy of permeability is consistent with the slice surface porosity distribution in 3D pore structure. The permeability in the horizontal direction is much greater than that in the vertical direction, indicating that the dominant transportation channel is along the horizontal direction of the studied coals. The research results achieve the visualization of the 3D complex structure of coal and fully capture and quantify pore size, connectivity, curvature, permeability, and its anisotropic characteristics at micron-scale resolution. This provides a prerequisite for the study of mass transfer behaviors and associated transport mechanisms in real pore structures.

Adjustable temperature and high thermal conductivity composite phase change material based on sodium acetate trihydrate–alanine/expanded graphite for thermal management of electronic devices

Phase change energy storage technology using phase change materials (PCMs) is a viable solution to effectively address the heat dissipation problems of electronic devices. Herein, we proposed to prepare a modified PCM using CH3COONa·3H2O (SAT) as main PCM, 9 wt% DL-Alanine (DL) as temperature modifier, and 2 wt% Na2HPO4·12H2O as nucleating agent. Calculations using density functional theory method confirmed that the adjustment of DL on phase change temperature of SAT was originated from the hydrogen bond between them. Then, the modified PCM was loaded into 14 wt% expanded graphite (EG) to obtain a composite PCM with a suitable phase change temperature of 52.9 °C, phase change enthalpy of 227.4 J/g as well as supercooling degree of 6.6 °C, and the thermal conductivity of the composite PCM was as high as 11.52 W·m−1·K−1. SEM and pore structure analyses showed that the modified PCM was successfully loaded into the pore structure of EG, and their combination was verified by XRD and FT-IR as a physical interaction. After 200 heating–cooling cycles, the phase change temperature and enthalpy of the composite PCM was basically unchanged along with consistent crystal structure and chemical composition, showing an excellent thermal reliability. A comparative analysis applied in a testing system showed that with loading of the composite PCM temperature control module, the critical time of the electronic chip was extended by 4670 s and the thermal equilibrium temperature was decreased by 20.4 °C, presenting a good thermal management performance. Therefore, the prepared composite PCM had great potential for application in thermal management of electronic devices.

Research on the effect of tuff powder on the properties of moderate-heat portland cement-based materials and the methods for evaluating pozzolanic activity

Tuff powder (TP) has attracted significant attention due to its abundant resources, low carbon emissions, and potential enhancements in concrete property. This study investigates the effect of TP on the mechanical properties, hydration behavior, pore structure, microstructure morphology, economic and environmental analysis of moderate-heat portland cement (MHPC), comparing it with MHPC-based materials containing fly ash (FA). The synergistic morphological effect and micro-aggregate filling action of FA and TP result in higher early strength in the fly ash-tuff powder (FT) group mortar. The CH content and chemically bounded water content of TP paste are higher, showing a better early hydration promotion effect. The pore structure of the composite cement mortar is changed due to the addition of the admixture. Furthermore, the multi-factor response strength and strength activity index (SAI) model were developed based on response surface methodology (RSM), linking to TP specific surface area, dosage, and specimen curing age. This provides a reference for more accurate and comprehensive prediction of cement mortar property, quantification of effects, optimization of mix proportions, and evaluation methods for the activity of pozzolanic materials.

Mechanism of air-entraining agent to improve the properties of coal-based solid waste backfill

Fly ash exhibits volcanic ash activity and can be utilized as a cementitious material to reduce filling costs. The limited flow characteristics of mine solid waste filling slurry can impact backfill efficiency. Instead of using a large amount of cement, we employ fly ash as a cementing material to prepare filling slurries with varying air-entraining agent dosages. The results indicate that as the air-entraining agent dosage increases from 0 to 8%, the fluidity of the filling slurry improves, and the strength increases within the first 5 days of curing. The strength of the filling increases initially from 5 to 28 days of curing with the increase in air-entraining agent dosage, reaching a peak at 4% dosage, with an 11.35% higher strength compared to the filling body without the air-entraining agent. The microscopic pore structure and hydration product analysis reveal that introducing an appropriate amount of bubbles results in an even distribution of cementitious material and aggregates, improving fluidity and strength. However, excessive addition of air-entraining agents inhibits the growth of C–S–H and the filling ability of AFt for primary pores, ultimately impacting the long-term strength growth of the filling body.

Influence of microwave curing on the early performance of heat-stored LC3 composites

Limestone calcined clay cement (LC3), as a new green cementitious material, has a wide range of functional applications in cement-based composite materials. Heat-stored LC3 effectively achieve energy-saving and carbon reduction in buildings. However, the addition of phase change material (PCM) particles leads to a significant decrease in strength, which imposes higher requirements on early performance. To address this issue, this study adopts microwave curing technology to rapidly enhance the early performance of heat-stored LC3, with a specific focus on the influence of microwave curing on the early mechanical properties, hydration products, and microstructure of heat-stored LC3. The results showed that microwave curing at a power of 320 W for 5 min increased the 3-day compressive strength of heat-stored LC3 by 87.3 %, without adversely affecting the later-stage strength, thus compensating for the deficiency in early strength. Microstructure and pore structure analysis revealed that the enhancement of early strength by microwave curing was mainly attributed to the promotion of early hydration of clinker and the activation of pozzolanic reaction occurred calcined clay. The additional formation of C-(A)-S-H gel reduced the matrix porosity, improved overall integrity, and enhanced the microstructure. Additionally, the temperature regulation capability of heat-stored LC3 was verified, ensuring its auxiliary temperature regulation function while maintaining reliable mechanical properties and excellent early strength.

A coral-like skeleton carbon aerogel achieves good mechanical and thermal insulation properties

A coral-like network carbon aerogel was synthesized by introducing acid-modified carbon nanofibers (a-CNF) into phenolic (PR) aerogel through chemical grafting, followed by high-temperature carbonization. The bonding interaction between a-CNF and PR was analyzed by FT-IR spectroscopy. The microstructure of a-CNF/PR composite aerogel (a-CNF/PRA) was studied by SEM and pore structure analysis. The results showed that introducing 5 wt% of a-CNF was most favorable for forming a porous network of a-CNF/PRA. SEM photographs and pore structure analysis indicated that a-CNF/C composite aerogel (a-CNF/CA) developed a stable porous skeletal structure during carbonization. TEM images revealed that the complete porous skeleton consisted of a-CNF encapsulated by carbon layers. The carbonization shrinkage of a-CNF/CA was only 26.53% due to the presence of a-CNF as the skeleton support. Compared to carbon aerogel, a-CNF/CA exhibited lower density (0.072 g cm−3), thermal conductivity (0.0452 W m−1 K−1), and higher compressive strength (up to 3.26 MPa) up to 3.26 MPa than that of carbon aerogel (1.21 MPa). These findings confirmed the excellent mechanical and thermal insulation properties of a-CNF/CA.

A new strategy for semi quantitative analysis of pore structure for lithium-ion battery electrodes

The Lithium ions diffusion dynamic, electrons transfer and the growth of the solid electrolyte interfaces are in close relation to the pore structure of the anodes. The widely used mercury intrusion porosimetry suffers from serious severe reaction with the copper and aluminum substrate, and unable to provide the pore structure evolution in the cross-section direction of the electrode. And the X-ray computed tomography faces limitations in identifying the carbon gel phase and is associated with high costs. Therefore, it is of substantial interest to directly investigate the cross-sectional pore structure from SEM morphologies. In this study, the using of resin protected polishing method to expose the cross-sectional structure is proposed to analyze the porosity evolution of the cross-sectional structure for lithium-ion battery anode. This method can clearly expose the cross-sectional structure of the electrode preventing the disturbance of the height fluctuation of the active particles. The influence of the coating processes on the pore structure is studied with the help of image J software and the machine leaning plug-in. The porosity changes of the electrode along with the coating depth are clearly elucidated. This method provides a convenient and efficient solution on the structure characterization of the electrode in Lithium-ion batteries.

Comparative study of hydro-mechanical behaviors of compacted bentonite powder and granular bentonite

In the deep geological disposal repository of high-level radioactive waste, buffer/backfill materials typically consist of compacted bentonite block and granular bentonite. As these materials undergo a long-term hydration, it is anticipated that the two forms of bentonite materials (i.e. compacted bentonite powder (CBP) and granular bentonite (GB)) are expected to exhibit differing hydro-mechanical behaviors due to the differences in their structures. This work aims to investigate the differences in swelling pressure and compressibility through a series of swelling pressure tests, compression tests and mercury intrusion porosimetry (MIP) tests. The experimental results demonstrated that swelling pressure curves of the CBP specimens showed higher first peak values and more pronounced collapse than those of the GB specimens at a given dry density, regardless of vapor-water hydration or liquid-water hydration. The final swelling pressures of the two materials were similar at the same dry density, suggesting an independent correlation between swelling pressure and dry density. At the high suction range, the compression curves exhibited an obvious bi-linear pattern for the CBP specimens and a significant nonlinearity for the GB specimens. Meanwhile, the CBP specimens presented higher pre-consolidation pressures and larger compression indices than the GB specimens at a given suction. As suction decreased, the compression curves of the two materials gradually approached each other and their differences were reduced accordingly. After reaching saturation, a good consistency between them was observed whether for final swelling pressure or compressibility. Pore structure analysis revealed that the two materials both presented an initially double structure, and their differences were primarily manifested at the macrostructural level. Eventually, the differences in swelling pressure or compression curves of the two materials were well interpreted by combining microstructural evolutions.

Nonlinear hydroelastic vibration of foamed concrete beams via peridynamic differential operator

Evaluating the hydroelastic responses of underwater cementitious structural elements is critical for ensuring the sustainability and durability of energy-saving marine infrastructures. Existing work on the hydroelastic analysis of porous structures has been mostly developed using the general elastic constitutive relation; however, it fails to capture the influence of saturation. To fill this knowledge gap, we for the first time propose a novel fluid-porous structure interactive model that incorporates the combined effects of hydrodynamic pressure and saturation-induced pore pressure. One more pioneering effort is to solve this nonlinear hydroelastic problem by introducing peridynamic differential operator (PDDO). It is worth noting that the introduction of PDDO removes the inherent drawback employing the local-theory based techniques, namely being prone to singularities arising from the presence of discontinuity. The accuracy and reliability of the proposed numerical framework are validated by comparing the results with the degraded model in the reported literature. Moreover, our results highlight that the angular frequencies are underestimated when ignoring the effect of saturation in foamed concrete beams. The presented method provides a profound understanding of the underwater structural dynamic monitoring that benefits the design of marine infrastructures.

Effect of Metastable Intermolecular Composites on the Thermal Decomposition of Glycidyl Azide Polymer Energetic Thermoplastic Elastomer.

Glycidyl azide polymer energetic thermoplastic elastomer (GAP-ETPE) has become a research hotspot due to its excellent comprehensive performance. In this paper, metastable intermolecular energetic nanocomposites (MICs) were prepared by a simple and safe method, and the catalytic performance for decomposition of GAP-ETPE was studied. An X-ray diffraction (XRD) analysis showed that the MICs exhibited specific crystal formation, which proved that the MICs were successfully prepared. Morphology, surface area, and pore structure analysis showed that the Al/copper ferrite and Al/Fe2O3 MICs had a large specific surface area mesoporous structure. The Al/CuO MICs did not have a mesoporous structure or a large surface area. The structure of MICs led to their different performance for the GAP-ETPE decomposition catalysis. The increase in specific surface area is a benefit of the catalytic performance. Due to the easier formation of complexes, MICs containing Cu have better catalytic performance for GAP-ETPE decomposition than those containing Fe. The conclusions of this study can provide a basis for the adjustment of the catalytic performance of MICs in GAP-ETPE propellants.