Calculation Of Pore Size Distribution Research Articles

Unraveling the influence of surface functionalities on gas Physisorption: A comprehensive study on SBA-15 nanoporous material from Monte Carlo simulation for improved Textural-Energetic characterization

In this study, we conducted experimental and Monte Carlo simulation studies in the grand canonical ensemble (GCMC) to investigate the role of molecular orientation and surface heterogeneity on the adsorption of N2 at 77 K. Our research focused on a series of ordered nanoporous materials (SBA-15) with varying degrees of oxygen functionalities. Specifically, we examined the effects of surface heterogeneity on the calculation of pore size distribution (PSD) and the Brunauer-Emmett-Teller (BET) area of porous materials. To provide a comprehensive perspective, we compared our results with three levels of surface oxidation, including a pristine case without any surface oxidation.The results from both our experimental and simulation data reveal the importance of chemical heterogeneity in determining equilibrium properties such as molecular packing within the pores, differential enthalpies of adsorption, and N2 orientation distribution. Our findings suggest that accurate characterization of surface heterogeneity is crucial for understanding gas adsorption in nanoporous materials and for developing better models for predicting their performance in various applications. Moreover, our simulations revealed substantial changes in the molecular orientation of adsorbate particles with increasing surface heterogeneity. This insight provides valuable information about the behavior of molecules within the nanoporous materials, further enhancing our understanding of the complex adsorption processes in these systems.

Conformational and static properties of tagged chains in solvents: effect of chain connectivity in solvent molecules.

Polymer chains immersed in different solvent molecules exhibit diverse properties due to multiple spatiotemporal scales and complex interactions. Using molecular dynamics simulations, we study the conformational and static properties of tagged chains in different solvent molecules. Two types of solvent molecules were examined: one type consisted of chain molecules connected by bonds, while the other type consisted of individual bead molecules without any bonds. The only difference between the two solvent molecules lies in the chain connectivity. Our results show a compression of the tagged chains with the addition of bead or chain molecules. Chain molecule confinement induces a stronger compression compared to bead molecule confinement. In chain solvent molecules, the tagged chain's radius of gyration reached a minimum at a monomer volume fraction of ∼0.3. Notably, the probability distributions of chain size remain unchanged at different solvent densities, irrespective of whether the solvent consists of beads or polymers. Furthermore, as solvent density increases, a crossover from a unimodal to a bimodal distribution of bond angles is observed, indicating the presence of both compressed and expanded regions within the chain. The effective monomer-solvent interaction is obtained by calculating the partial radial distribution function and the potential of the mean force. In chain solvents, the correlation hole effect results in a reduced number of nearest neighbors around tagged monomers compared to bead solvents. The calculation of pore size distribution reveals that the solvent nonhomogeneity induced by chain connectivity leads to a broader distribution of pore sizes and larger pore dimensions at low volume fractions. These findings provide a deeper understanding of the conformational behavior of polymer chains in different solvent environments.

Evolution of pore structure in nanoparticle deposits from unimodal to bimodal pore size distributions: Focus on structural features of dendritic structures

Nanoparticle deposits can exhibit various structures, including compact and dendritic structures, depending on the deposition conditions. While previous studies have characterized deposit structures using factors such as porosity and spatial autocorrelation index, the pore size distribution (PSD), which is an essential structural property, has only been explored in compact structures. In this study, we investigate the PSDs of the entire nanoparticle deposits, ranging from compact to dendritic structures. Deposits are formed using an off-lattice Monte Carlo simulation, and deposition conditions are represented by two dimensionless numbers (KnD, χF). The diffusive Knudsen number (KnD) ranges from 10−1.5 to 101.5, while the dimensionless translational energy of a particle (χF) ranges from 10−3 to 101.5. We use the Delaunay triangulation algorithm for fast PSD calculation, and validate the calculation method using theoretical values of ideal structures and experimental literature data. Our results show that bimodal PSDs appear under thermally-dominated conditions with high values of KnD, while unimodal PSDs with a constant mode radius (∼2.5 rp) are observed under highly advective conditions with high values of χF. We present the geometric mean radii and mode radii of pores as color-filled contours to show their variation trends with KnD and χF. Additionally, we propose a simple model that predicts dendrite width by combining the overall porosity and mode radii of pores. Our model's predictions reasonably match the dendrite width data obtained using a density-based clustering algorithm.

Investigation on strong vertical permeability and micro-pore characteristics of Jinan red clay using X-ray micro-tomography

Due to the peculiarity of the spring domain strata in Jinan, the phenomenon of serious water seepage appears in the process of excavation. The macro permeability of soil is closely correlated with its microstructure. In this study, using the X-ray micro-tomography (micro-CT) system and a self-designed soil seepage device, the internal pore structure of Jinan red clay and the water flow inside the sample under different seepage stages were observed. The microstructure of water phase and air phase in the sample was segmented by the watershed algorithm. Calculation and comparison of pore and throat size distributions and coordination number (CN) at different seepage stages were conducted by establishing pore network model (PNM). Meanwhile, the seepage experiment simulations were conducted based on the 3D pore structure of red clay. The results show that the preferentially flow of Jinan red clay is obvious due to the existence of the vertically developed macropore channel. The fine particles (mainly silt particles) are washed away during seepage, thereby expanding the pore channels. The maximum pore radius and pore connectivity have important influence on seepage characteristics of Jinan red clay, but the correlation between porosity is small.

An improved procedure for calculating the pore size distribution of filter cloths in capillary flow porometry

Pore size distribution is one of the most important structural characteristics of filter cloths and can, in theory, be used to predict filtration performance. Capillary flow porometry is a common method to determine the pore diameter(s) and the pore size distribution of a porous material. Equipment applying this method has many advantages, but data processing and further calculations still require refining to be fit for purpose in calculations of flow capacity. The present study aims to develop a new procedure for processing volumetric flow rate data and corresponding pressure, which are measured by capillary flow porometry. The processed data are further used to calculate the pore size distribution of textile materials. Six industrial samples of polypropylene filter cloth were examined using scanning electron microscopy and capillary flow porometry. The raw data measured by the capillary flow porometer were processed using the developed method that considers changes in flow regimes as pressure increases. In addition, the nonideality of pores, originating from tortuosity, an irregular cross-sectional shape of the pore, and the number of pores, were considered in calculations by combining all these characteristics in one single parameter. This work shows that pores in a textile material are not ideal cylinders. The standard pore size distribution calculations should consider an imperfect pore structure and, therefore, be corrected.

Estimation of shale pore-size-distribution from N2 adsorption characteristics employing modified BJH algorithm

Accurate pore-size-distribution (PSD) is the key to comprehending porous media and shale rock characteristics. There are multiple methods for calculating the PSD of porous media. The Barrett–Joyner–Halenda (BJH) method is the most widely used and simplest calculation, and therefore, this study focus on the BJH algorithm to discuss the accurate shale PSD based on N2 adsorption characteristics. Despite conducting more than a hundred experiments there are certain phenomena for which the calculated pore volume is smaller than the actual pore volume. Therefore, we combined the Brunauer–Emmet–Teller (BET) multilayer adsorption theory and Halsey adsorption equation to analyze the capillary evaporation and desorption demarcation points in the desorption isotherm of each shale sample, and a modified PSD calculation model was established. In addition, we applied the modified BJH algorithm to a homogeneous silicon material with the pore radius known, for calculating the theoretical pore radius and subsequently the pore radii; this allowed determining the correctness of the modified algorithm. The calculation error was approximately 5% that indicated the accuracy of this algorithm. Therefore, this study could provide meaningful insights into the accurate PSD calculation and gas-in-place estimation in shale nanoporous media.

Revealing Molecular Mechanisms in Hierarchical Nanoporous Carbon via Nuclear Magnetic Resonance

Author(s): Mao, H; Tang, J; Xu, J; Peng, Y; Chen, J; Wu, B; Jiang, Y; Hou, K; Chen, S; Wang, J; Lee, HR; Halat, DM; Zhang, B; Chen, W; Plantz, AZ; Lu, Z; Cui, Y; Reimer, JA | Abstract: Hierarchical nanoporous carbons combining pore sizes of different length scales are highly important for separation processes. However, critical questions remain regarding the hierarchical structure regulation and the molecular mechanisms of gaseous adsorbate uptake and interactions within the hierarchical nanoporous carbons. These materials present characterization challenges in that there are no experimental techniques that can elucidate the molecular mechanisms of the organic compounds and CO within the materials. We deployed multidimensional solid-state nuclear magnetic resonance (NMR) to generate maps of guest-framework interactions as a function of adsorbate concentrations and adsorption times. The NMR spectra provide insight toward the design of effective hierarchical pore structures. Our materials show a high volatile organic compounds/CO physisorption capacity, which reveals promising application to carbon-capture strategies to mitigate global warming. 2 2

Computational predictions of porosities, pore size distributions, and conductivities of aerosol deposited particulate films

The structure and resulting physical properties of aerosol deposited particulate films are governed by the size distribution and morphology of the depositing particles as well as the physics governing particle deposition. While particulate film deposition processes are qualitatively understood, the link between particle characteristics and deposition physics to film properties has not been probed systematically. Here we apply a combination of Langevin dynamics deposition simulations, Monte Carlo pore size distribution calculations, and predictions of thermal conductivities to better establish such process parameter-film property relationships. We account for partial coalescence, polydispersity, and aggregate deposition. We establish that the deposition of polydisperse and aggregated particles leads to broadening of the pore size distribution function and an increase in the mode pore size. Via a non-continuum gas conductivity model, we show that aerosol deposited films can achieve porosities and thermal conductivities similar to conventional aerogels.

A comparison of nano-scale pore attributes of Barakar Formation gas shales from Raniganj and Wardha Basin, India using low pressure sorption and FEG-SEM analysis

This study investigates the micropore-mesopore spectrum in gas shales by augmenting two different pore size distribution calculation methods using two probe gases in low-pressure sorption analysis. The Barakar Formation shale samples collected from Wardha and Asansol belonging to two key potential basins in India, namely Wardha and Raniganj, were studied to identify possible variations in pore attributes in shales, and a comparison was drawn. A combination of CO2 and N2 low-pressure gas adsorption studies was implemented to resolve micro- and meso-pores, using the respective probe adsorbate. The visual representation of the pore structure and its disposition was facilitated by high-resolution microscopic imaging, and aided by image analysis. The results show a positive correlation between clay mineral composition and the mesopore attributes as well as organic matter composition and micropore attributes. This confirms that both inorganic and organic content of shales contains large pore volumes, albeit in different pore dimension ranges with some overlap. High N2 adsorption potential of Asansol shale, as well as high CO2 adsorption potential of Wardha valley shale, is conformable with their respective pore size distributions. Fractal characteristics of mesopores suggest that the larger mesopores have a rougher surface, whereas the smaller mesopores have a smoother surface (with average fractal dimensions of 2.6 and 2.2, respectively). Although all examined shales belong to the same geological formation, they exhibit distinctly variable pore attributes and gas storage potential.

Exploiting the adsorption of simple gases O2 and H2 with minimal quadrupole moments for the dual gas characterization of nanoporous carbons using 2D-NLDFT models

For years, the characterization of carbon pore size distribution (PSD) has been dominated by the analysis of N2 isotherms. Recently, the IUPAC Technical Report (2015) recommended Ar as inert gas for this analysis. N2 molecule due to its significant quadrupole moment may selectively interact with the polar surface sites and affect the isotherm measurement. CO2, another gas that is often used for the characterization of microporous carbons exhibits even higher quadrupole moment than N2. In the present study, we substitute N2 and CO2 with O2 and H2 gases that have much lower quadrupole moments. The PSD calculations are performed using molecular models based on classical and quantum corrected two-dimensional nonlocal density functional theory (2D-NLDFT).We compare the results of the dual gas analysis methods by the simultaneous fit of our models to N2 & CO2, and O2 & H2 isotherms for several reference carbon samples and demonstrate consistency between the results derived from both pairs of isotherms.A fundamental and practical benefit of using the dual gas analysis method is the ability to obtain the full micro and mesopore PSD by using a partial O2 isotherm without low-pressure data in combination with full H2 isotherm both measured at 77 K.

PyGAPS: a Python-based framework for adsorption isotherm processing and material characterisation

Material characterisation through adsorption is a widely-used laboratory technique. The isotherms obtained through volumetric or gravimetric experiments impart insight through their features but can also be analysed to determine material characteristics such as specific surface area, pore size distribution, surface energetics, or used for predicting mixture adsorption. The pyGAPS (Python General Adsorption Processing Suite) framework was developed to address the need for high-throughput processing of such adsorption data, independent of the data origin, while also being capable of presenting individual results in a user-friendly manner. It contains many common characterisation methods such as: Brunauer–Emmett–Teller and Langmuir surface area, t and αs plots, pore size distribution calculations (Barrett–Joyner–Halenda, Dollimore–Heal, Horvath–Kawazoe, DFT/NLDFT kernel fitting), isosteric enthalpy calculations, ideal adsorbed solution theory calculations, isotherm modelling and more, as well as the ability to import and store data from Excel, CSV, JSON and SQLite databases. In this work, a description of the capabilities of pyGAPS is presented. The code is then be used in two case studies: a routine characterisation of a UiO-66(Zr) sample and in the processing of an adsorption dataset of a commercial carbon (Takeda 5A) for applications in gas separation.

Predicting Intrinsic Permeability of a Double Porosity Cellular Ceramic Using X-ray Micro-tomography

The microstructure of a porous cellular ceramic exhibiting two spatial characteristic lengths was characterized to determine parameters of its pore space morphology and connectivity. In order to assess the hierarchical microstructure, X-ray computed micro-tomography was employed as an imaging technique to supply three-dimensional images in two spatial scales. Two samples, at different sintering temperatures, were produced by emulsification of sunflower oil in aqueous aluminum oxide suspensions using gelatin bloom 90 as the gelling agent, dodecyl sodium sulfate as the surfactant and native cassava starch as the gelling and porogenic agent. Image processing and morphological characterization were performed on each spatial scale, individually allowing the calculation of the total porosity and pore size distribution of the ceramic sample. For the numerical simulation of the intrinsic permeability, representative images of the two spatial scales were superposed in a single super-image. This simulation was performed on the 3D pore network extracted from the super-image. The simulated permeability results were interpreted on the basis of the microstructure.

Consistency of carbon nanopore characteristics derived from adsorption of simple gases and 2D-NLDFT models. Advantages of using adsorption isotherms of oxygen (O2) at 77 K

The pore size distribution (PSD) of porous carbons is most often derived from the analysis of standard N2 and Ar adsorption isotherms measured at 77 and 87 K. From the two gases, Ar is recommended (IUPAC Technical Report 2015) as more reliable for the PSD analysis due to its minimal specific interactions with the surface polar groups. Such interactions may influence the adsorption of N2 molecules due to its significant quadrupole moment. In practice, however, using liquid Ar as a cryogen for Ar adsorption measurements may be challenging because of its high cost and limited availability in various parts of the world. In this study, we propose using O2 adsorption isotherms for the PSD characterization of porous carbons. The quadrupole moment of O2 is less than one-third of the value reported for N2, and thus its susceptibility to specific interactions with polar groups is much smaller than that of N2. We demonstrate a quantitative agreement between the PSD results derived from the adsorption isotherms of O2 and N2 measured at 77 K, and Ar at 87 K on four representative carbon samples. The PSD calculations are performed using adsorption models based on the two-dimensional non-local density functional theory (2D-NLDFT).

Influence of the Pore Shape and Size Distribution in Hierarchically Porous Electrodes on Energy and Power Densities of Electrochemical Devices

The microporous-mesoporous hierarchical structure of nanostructural carbon and modified carbon materials has a strong influence on the electrochemical characteristics of the electrical energy conversion and storage devices [1-4]. To improve the mass transfer rate, the understanding of the accumulation mechanisms of the ions in microporous-mesoporous materials is inevitable having huge impact on the power and energy density characteristics of supercapacitors, Li- and Na-ion batteries as well as fuel cells. Therefore, it is crucial to have a good understanding of the graphitization level, porosity and hierarchical structure of carbon and modified carbon materials used [1-5]. Therefore, systematical analysis of the gas adsorption, Raman, X-ray diffraction, scanning electron microscopy, photoelectron spectroscopy (including synchrotron beam based method), high-resolution transmission electron microscopy (with EELS and SAED) and small-angle neutron scattering data for various carbon materials prepared by high-temperature chlorination, hydrothermal carbonization, etc. methods will be given. Comparison with small-angle X-ray scattering data [6] will be given. The data obtained by gas-phase analysis methods will be compared with cyclic voltammetry, constant current charge/discharge, electrochemical impedance and constant power discharge data. Influence of electrolyte chemical composition, solvent characteristics (aqueous and non-aqueous) and ionic liquids with and without non-aqueous solvent additions will be discussed in combination with hierarchical porosity, graphitization level and particle size analysis data. All carbon samples were very carefully reduced with hydrogen at 800 оC, thereafter dried under vacuum at 350 оC at least for 24 h priori each measurement. N2 sorption analysis at -196 оC, Ar at -186 oC and CO2 sorption analysis at 0 оC were carried out on an ASAP 2020 instrument (Micromeritics, USA). The experimental data were treated with classical models (BET and t-plot) as well as different NLDFT models available through 3Flex and SAIEUS (Micromeritics, USA) software [7,8]. The results for pore size distribution (PSD) calculations from N2 isotherms using a slit shape pore model and model “Carbon-N2, 2D-NLDFT Heterogeneous Surface” [9,10] (SAIEUS, Micromeritics, USA) will be reported. The pore size distribution data calculated from CO2 sorption isotherms using a slit shaped pore model and model “CO2-DFT Model” (software 3Flex, Micromeritics, USA) will be discussed. Although, the pore size distributions calculated from CO2 have high level of roughness and several model artefacts (e.g. around 0.7 nm) [11,12], the results generally support the findings from N2 sorption isotherms. In addition, Raman spectra analysis, small-angle neutrons scattering and small angle X-ray scattering combined with the FIB-SEM and HR-TEM data will be discussed. The results obtained will be compared to the behavior of these materials in different energy storage/conversion related devices like supercapacitors [1-6] and Li- and Na-ion battery negatively charged electrodes [4]. Thus, the importance of graphitization level, hierarchical porous structure and pore shape along with pore size distribution data for carbon materials energy and power densities will be addressed and demonstrated. Acknowledgments Authors would like to thank HZB and PSI for the allocation of neutron radiation beamtime on instruments V16 and FOCUS, respectively; and The Estonian Ministry of Education and Research (institutional research project IUT20-13, personal research grant PUT55) and European Regional Development Fund (The Centres of Excellence 3.2.0101–0030 and 2014-2020.4.01.15-0011) for financial support.

Application of NMR T2 to Pore Size Distribution and Movable Fluid Distribution in Tight Sandstones

This paper explores the applicability of nuclear magnetic resonance (NMR) technology on pore size distribution (PSD) and movable fluid distribution (MFD) in tight sandstones. Centrifugation experiments and NMR tests are performed on saturated samples. The fluid changes in pores corresponding with three different types of NMR T2 distribution after each centrifugation is then analyzed. In addition, a new method to determine the conversion factor from NMR T2 distribution to PSD is developed. In comparison with the PSD obtained by mercury intrusion porosimetry, the new method is more suitable for PSD calculation in tight sandstones. Afterward, the optimum centrifugal force to determine the threshold radius for fluid flow is obtained. On the basis of this, we analyze MFD in tight formation. Through study, the following results are arrived at: patterns of NMR T2 distributions of outcrop and subsurface cores at water saturation condition can be classified into three types (I, II, and III). Among which, type I an...

Influence of the Pore Shape and Size Distribution in Hierarchically Porous Electrodes on Energy and Power Densities of Electrochemical Devices

The microporous-mesoporous structure of nanoporous carbon and modified carbon electrodes has a strong influence on the electrochemical characteristics of the devices like supercapacitors, polymer electrolyte fuel cells and electrolysers, gas storage devices, as well as of Li-ion and Na-ion batteries. For that reason, it is crucial to have a good understanding of the porosity and hierarchical structure of carbon and modified carbon materials used [1]. As a standard method, the nitrogen adsorption measurements and various analysis theories are used. These models need the pore shape as an input parameter for detailed calculations, however, often the slit-shaped pore model is postulated without additional verification [1]. This assumption is also very often transferred to the behaviour of carbon based materials in different applications leading to some serious misinterpretations. For cost-effective hydrogen and methane based economy, efficient methods for hydrogen and methane storage are urgently needed. To improve the gas storage properties, the fundamental understanding of the confinement of the gas in microporous-mesoporous materials is inevitable. In particular, the role of confinement dimensions in the mass transfer of the hydrogen, methane as well as oxygen molecules has huge impact on the fuel cell characteristics. Our research focuses on detailed estimation of pore shape and size in various carbide-derived carbons and other carbon materials using various standardized and novel methods, like nitrogen, hydrogen and carbon dioxide adsorption measurements. All carbon samples were dried under vacuum at 350 оC at least for 24 h prior to each measurement. N2 sorption analysis at -196 оC and CO2 sorption analysis at 0 оC were carried out on an ASAP 2020 instrument (Micromeritics, USA). The experimental data were treated with classical models (BET and t-plot) as well as different NLDFT models available through 3Flex and SAIEUS (Micromeritics, USA) software [2,3]. The results for pore size distribution (PSD) calculations from N2 isotherms using a slit shape pore model and model “Carbon-N2, 2D-NLDFT Heterogeneous Surface” [4,5] (demo software SAIEUS, Micromeritics, USA) will be reported. The pore size distribution data calculated from CO2 sorption isotherms using a slit shaped pore model and model “CO2-DFT Model” (software 3Flex, Micromeritics, USA) will be discussed. Although, the pore size distributions calculated from CO2 have high level of roughness and several model artefacts (e.g. around 0.7 nm) [6,7], the results generally support the findings from N2 sorption isotherms. Raman spectra analysis, small-angle neutrons scattering and small angle X-ray scattering combined with the FIB-SEM and high resolution TEM data have been used. The results obtained are compared to the behaviour of these materials in different energy storage/conversion related devices like supercapacitors [8,9] and polymer electrolyte fuel cells 10]. As a result, the importance of hierarchical porous structure and pore shape along with pore size (pore size distribution) of used carbon materials in the energy technology applications will be addressed and demonstrated. The hydrogen sorption parameters will be compared with the methane sorption characteristics as well as correlated with PEM fuel cell and supercapacitor characteristics. Acknowledgments Authors would like to thank HZB and PSI for the allocation of neutron radiation beamtime on instruments V16 and FOCUS, respectively. The Estonian Ministry of Education and Research (institutional research project IUT20-13, personal research grant PUT55) and European Regional Development Fund (The Centres of Excellence TK117 and, TK141) for financial support.

New pore size distribution calculation model based on chord length and digital image

In this study, we propose a model to calculate pore size distribution based on the chord length and digital image. First, the chord length cumulative frequency function of the unit circle is deduced. Next, a dimensionless chord length cumulative frequency function of the arbitrary size circle is derived. The chord length data are generated by cutting a combination of the specific step size of the pore size in varying proportions. Conversely, the value of the chord length is also obtained from the segmented CT image data by direct calculation. Using the dimensionless chord length cumulative frequency function, we formulate the balance equation, which indicates that the chord length distribution generated by cutting a combination of the specific step size of the pore size in varying proportions is the same as the chord length distribution that is obtained from direct calculation in the segmented CT image data. By solving the balance equation, the pore size distribution is obtained. Our model calculation results are compared with the max ball model calculation results. Furthermore, the pore size distribution of the shale sample is calculated based on our model. The results indicate that pore radii mostly less than 50 nm and small pores are dominant in shale.

Morphologically disordered pore model for characterization of micro-mesoporous carbons

We present a new morphologically disordered slit-shaped pore (MDSP) model for simulating gas adsorption in micro-mesoporous carbonaceous materials. The MDSP model qualitatively accounts for the inherent roughness of carbon pore walls in accord with the atomistic structural model of LMA10 reference carbon material. The MDSP model is applied to pore size distribution (PSD) calculations from nitrogen adsorption isotherms measured at 77.4 K in the range of pore widths from 0.72 to 40 nm. The MDSP model improves significantly the nitrogen adsorption porosimetry and, being fully atomistic, it is transferable to study various adsorbate-adsorbent systems. Computations of PSD functions for a series of carbonaceous materials, including activated carbon fiber, granular activated carbons, synthetic activated carbons showed that MDSP generates smooth Gaussian-type PSD functions with a well-defined average pore size. Furthermore, PSD functions computed from the MDSP model are free from the artificial gaps in the region of narrow micropores (∼1 nm and ∼2 nm) predicted from the standard slit-shaped pore models with ideal graphite-like walls. MDSP is not only a complementary model to existing approaches, such as quench-solid density functional theory method, but it paves the way to efficient atomistic simulations of various compounds within morphologically disordered carbon nanopores.

Analysis and Visualization of 2D and 3D Grain and Pore Size ofFontainebleau Sandstone Using Digital Rock Physics

Fontainebleau sandstone is sandstone found in one of the cities in France. This sandstone has unique characteristics, which is a clean-fme sandstone, composed of 99% quartz, virtually devoid of clay, with the grain size of about 200 μm. Fontainebleau sandstone is widely used as a reference in the study of rock microstructure analysis and modelling. In this work analysis regarding the grain and pore size of Fontainebleau is presented. Calculation of 2D pore size and grain size distribution were done on the 299 slice of digital image of the Fontainebleau sandstone using Feret's diameters, equivalent diameters (d = 4A/P), and by means of local thickness/separation using plate model. For the 3D grain and pore size distribution, calculation of local thickness and local separation of the structure were used. Two dimensional analysis by means of Feret's diameter and equivalent diameter reveal that both grain and pore size distributions are in the form of reverse-J shaped (right skewed) while the local thickness/separation approach produces almost similar to symmetric Gaussian distribution. Three dimensional analysis produces fairly symmetric Gaussian distribution for both the grain and pore size. Further image processing were conducted and were succeed in producing three dimensional visual of the colour coded structure thickness (grain related) and structure separation (pore related).

Comparison of heterogeneous pore models QSDFT and 2D-NLDFT and computer programs ASiQwin and SAIEUS for calculation of pore size distribution

The pore size distributions (PSD) of selected carbons were calculated from their nitrogen adsorption isotherms using both the QSDFT model implemented in ASiQwin version 3.0 software (Quantachrome Instruments) and 2D-NLDFT model implemented in SAIEUS software (Micromeritics). The results showed that both the QSDFT and the 2D-NLDFT methods give similar PSDs despite the different methods for accounting for the heterogeneity of the carbon adsorbent. The characteristic features of the methods and software were discussed and possible improvements were proposed.