Pore Volume Distribution Research Articles

Mississippian Meramec lithologies and petrophysical property variability, stack trend, Anadarko Basin, Oklahoma

Mississippian Meramec reservoirs of the Sooner Trend in the Anadarko (Basin) in Canadian and Kingfisher Counties (STACK) play are comprised of silty limestones, calcareous siltstones, argillaceous calcareous siltstones, argillaceous siltstones, and mudstones. We found that core-defined reservoir lithologies are related to petrophysics-based rock types derived from porosity-permeability relationships using a flow-zone indicator approach. We classified lithologies and rock types in noncored wells using an artificial neural network (ANN) with overall accuracies of 93% and 70%, respectively. We observed that mudstone-rich rock type 1 exhibits high clay and relatively low calcite, whereas calcareous-rich rock type 3 has high calcite and low clay content with rock type 2 falling in between as a balance between rock types 1 and 3. Results of the ANN were applied to a suite of well logs in noncored wells in which we generated lithology and rock-type logs for the Meramec. We identified that the Meramec consists of seven stratigraphic units characterized as strike-elongate, shoaling-upward parasequences; each parasequence is capped by a marine-flooding surface. The lower three parasequences (lower Meramec) form a retrogradational parasequence set that back steps to the northwest and is capped by a maximum flooding surface. The upper Meramec is characterized by parasequences that form an aggradational to progradational stacking pattern followed again by a retrogradational trend. We predict that the parasequence stacking, associated lithology distribution, and diagenetic cements appear to control the spatial distribution of petrophysical properties (porosity, permeability, and water saturation), pore volume, and hydrocarbon pore volume (HCPV). Calcareous-rich lithologies exhibit lower porosity, permeability, HCPV, and higher water saturation. We deduced that argillaceous-rich lithologies that occur near the maximum flooding surface are the most favorable reservoir intervals because they exhibit relatively higher porosity, permeability, HCPV, and lower water saturation. Productivity could not be directly correlated to rock types as operational and completion factors as well as overpressure and oil phase play important roles on production.

Coal tar pitch-based hierarchical porous carbons prepared in molten salt for supercapacitors

As electrode materials for supercapacitors (SCs), hierarchical porous carbons (HPCs) have attracted tremendous attention due to their high specific surface area (SSA) and hierarchical pore structure. However, the complex template preparation process for HCPs usually brings high cost. Here, by combining the pre-carbonizing process of coal tar pitch (CTP) in eutectic salt (ZnCl2–NaCl, denoted as MZS, Sm260 °C) with the KOH activating process, HPCs with high capacitive performance have been prepared. The pre-carbonizing process is carried out under atmosphere to obtain the primitive carbon (PC), during which the MZS will not only provide a liquid environment for catalytic cross-linking of CTP but also act as the porogen agent. The effects of temperatures, heating rates, the mass ratio of KOH to PC (mKOH/mC) and the activating temperatures on the structure and capacitive properties of HPCs are explored. The results show that the HPCs prepared by activating the optimal PC (prepared at 560 °C in the MZS with a heating rate of 2.5 °C min−1) at temperature of 800 °C (heating rate of 10.0 °C min−1 and mKOH/mC ratio of 5) exhibit high specific surface area (2984 m2 g−1), large total pore volume (2.2 cm3 g−1) and wide pore size distribution. Based on the two-electrode test system, the optimal HCP shows a specific capacitance of 320 F g−1, the symmetric cells exhibit an energy density of 10.6 Wh kg−1 at power density of 50.1 W kg−1. Furthermore, the cell displays a good cyclic stability (the capacitance retention of 94.0% after 10,000 cycles). This strategy may be developed as a promising method for preparing high-performance HPC from CTP.

Nanometer Pore Structure Characterization of Taiyuan Formation Shale in the Lin-Xing Area Based on Nitrogen Adsorption Experiments

Ordos Basin is an important continental shale gas exploration site in China. The micropore structure of the shale reservoir is of great importance for shale gas evaluation. The Taiyuan Formation of the lower Permian is the main exploration interval for this area. To examine the nanometer pore structures in the Taiyuan Formation shale reservoirs in the Lin-Xing area, Northern Shaanxi, the microscopic pore structure characteristics were analyzed via nitrogen adsorption experiments. The pore structure parameters, such as specific surface area, pore volume, and aperture distribution, of shale were calculated; the significance of the pore structure for shale gas storage was analyzed; and the main controlling factors of pore development were assessed. The results indicated the surface area and hole volume of the shale sample to be 0.141–2.188 m2/g and 0.001398–0.008718 cm3/g, respectively. According to the IUPAC (International Union of Pure and Applied Chemistry) classification, mesopores and macropores were dominant in the pore structure, with the presence of a certain number of micropores. The adsorption curves were similar to the standard IV (a)-type isotherm line, and the hysteresis loop type was mainly similar to H3 and H4 types, indicating that most pores are dominated by open type pores, such as parallel plate-shaped pores and wedge-shaped slit pores. The micropores and mesopores provide the vast majority of the specific surface area, functioning as the main area for the adsorption of gas in the shale. The mesopores and macropores provide the vast majority of the pore volume, functioning as the main storage areas for the gas in the shale. Total organic carbon had no notable linear correlation with the total pore volume and the specific surface area. Vitrinite reflectance (Ro) had no notable correlation with the specific surface area, but did have a low “U” curve correlation with the total pore volume. There was no relationship between the quartz content and specific surface area and total pore volume. In addition, there was no notable correlation between the clay mineral content and total specific surface area and total pore volume.

Synopsis of Factors Affecting Hydrogen Storage in Biomass-Derived Activated Carbons

Hydrogen (H2) is largely regarded as a potential cost-efficient clean fuel primarily due to its beneficial properties, such as its high energy content and sustainability. With the rising demand for H2 in the past decades and its favorable characteristics as an energy carrier, the escalating USA consumption of pure H2 can be projected to reach 63 million tons by 2050. Despite the tremendous potential of H2 generation and its widespread application, transportation and storage of H2 have remained the major challenges of a sustainable H2 economy. Various efforts have been undertaken by storing H2 in activated carbons, metal organic frameworks (MOFs), covalent organic frameworks (COFs), etc. Recently, the literature has been stressing the need to develop biomass-based activated carbons as an effective H2 storage material, as these are inexpensive adsorbents with tunable chemical, mechanical, and morphological properties. This article reviews the current research trends and perspectives on the role of various properties of biomass-based activated carbons on its H2 uptake capacity. The critical aspects of the governing factors of H2 storage, namely, the surface morphology (specific surface area, pore volume, and pore size distribution), surface functionality (heteroatom and functional groups), physical condition of H2 storage (temperature and pressure), and thermodynamic properties (heat of adsorption and desorption), are discussed. A comprehensive survey of the literature showed that an “ideal” biomass-based activated carbon sorbent with a micropore size typically below 10 Å, micropore volume greater than 1.5 cm3/g, and high surface area of 4000 m2/g or more may help in substantial gravimetric H2 uptake of >10 wt% at cryogenic conditions (−196 °C), as smaller pores benefit by stronger physisorption due to the high heat of adsorption.

Template-free method for the synthesis of high-pore-volume γ-Al2O3 nanofibers in a membrane dispersion microreactor

Mesoporous γ-Al2O3 nanofibers with high pore volume and uniform pore size distributions were successfully synthesized via a template-free method in a membrane dispersion microreactor followed by calcination. The effects of crystal temperature, pH values, continuous phase concentration and washing solvent on the γ-Al2O3 nanofibers were carefully studied. The results showed that the as-obtained γ-Al2O3 nanofibers showed a length of 40–60 nm and a width of 3.2–3.4 nm, which were attributed to the high microscopic mixing rate in the membrane dispersion microreactor. Moreover, the precursors of γ-Al2O3 nanofibers treated with deionized water and mixed deionized water/alcohol solution had high pore volumes, reaching to 1.60 ml g−1 and 2.00 ml g−1, respectively. Furthermore, the adsorption performance of γ-Al2O3 nanofibers with high pore volumes was also investigated. These fibers showed an excellent adsorption capacity of 1323.68 mg g−1 for the removal of Congo red from aqueous solution, thereby indicating their potential for applications in adsorption and other related areas.

A new and integrated imaging and compositional method to investigate the contributions of organic matter and inorganic minerals to the pore spaces of lacustrine shale in China

Pore structure is an important factor controlling the shale gas content. Field-emission scanning electron microscopy (FE-SEM) is a commonly used shale reservoir characterization method. However, the quantitative characterization of shale pore structure based on FE-SEM results is still problematic due to the representative issue caused by strong heterogeneity at the microscale. In this study, FE-SEM images of lacustrine shale samples from the Jurassic Ziliujing Formation in the Northeastern Sichuan Basin were systematically analyzed using image processing software. The quantitative pore structure characteristics of each component (including organic matter, clay minerals, quartz and feldspar) in shale samples were extracted from the FE-SEM images. Using the areal porosity and pore size distribution from FE-SEM images, content and density of each component in shale samples and the bulk density of shale samples, the pore volume distribution of each component and the whole shale sample was calculated, which innovatively combined the FE-SEM images with shale compositional information to resolve the representative issue of FE-SEM images and was more practical. This new method could also avoid the effect of ink-bottle pores and isolated pores on shale pore structure characterization commonly existing in high-pressure mercury intrusion porosimetry (HPMIP). The results show that clay mineral pores dominantly contribute to the pore spaces of Ziliujing Formation shale, followed by quartz and feldspar pores, and organic matter (OM) pores contribute the least. The OMs are divided into four categories according to their pore sizes and morphology. More specifically, spongy pores in OM and the cracks within or along the periphery of nonporous OM are the dominant OM pore types in Ziliujing Formation shale. Furthermore, the interaction between clay minerals and organic matter could catalyze the process of pore development in OM, which is confirmed by the higher areal porosities of OMs contacting with clay minerals compared with those not.

The Pore-filling Effect of Bulk Graphite According to Viscosity of Impregnant

Pores produced by carbonization in bulk graphite process degrade the mechanical and electrical properties of bulk graphite. Therefore, the pores of bulk graphite must be reduced and an impregnation process needs to be performed for this reason. In this study, bulk graphite is impregnated by varying the viscosity of the impregnant. The pore volume and pore size distribution, according to the viscosity of the impregnant, are analyzed using a porosimeter. The total pore volume of bulk graphite is analyzed from the cumulative amount of mercury penetrated. The volume for a specific pore size is interpreted as the amount of mercury penetrating into that pore size. This decreases the cumulative amount of mercury penetrating into the recarbonized bulk graphite after impregnation because the viscosity of the impregnant is lower. The cumulative amount of mercury penetrating into bulk graphite before impregnation and after three times of impregnation with 5.1cP are 0.144 mL/g and 0.125 mL/gm, respectively. Therefore, it is confirmed that the impregnant filled the pores of the bulk graphite well. In this study, the impregnant with 5.1 cP, which is the lowest viscosity, shows the best effect for reducing the total pore volume. In addition, it is confirmed by Raman analysis that the impregnant is filled inside the pores. It is confirmed that phenolic resin, the impregnant, exists inside the pores through micro-Raman analysis from the inside of the pore to the outside.

Impact of pore distribution characteristics on percolation threshold based on site percolation theory

In order to better simulate the porous media with different pore distribution characteristics, this paper introduced a pore distribution factor m (m represents the randomly generated pore volume in the site percolation model, which is expressed by the number of sites)into the classic site percolation model. On this basis, the influence of pore distribution characteristics of two-dimensional (2D) and three-dimensional (3D) porous media on the percolation threshold is studied using numerical simulations. The study found that, when the porosity is the same, larger the value of m, smaller the number of pores in both the simulated 2D and 3D porous media. The decrease in the number of pores leads to the changes in the pore volume distribution characteristics. The shape of each pore, generated using the simulation in this paper, is random, due to which, larger the value of m is, easier it is for pores to merge to form larger pore clusters, which result in a reduction in the percolation threshold. The percolation threshold of 2D (lattice type: square) and 3D (lattice type: simple cubic) site percolation models decreases with the increase in the value of m. When the value of m is unity, the percolation thresholds of 2D and 3D porous media are found to be 59.27% and 31.16%, respectively, which are in agreement with the existing research results. When the value of m increases to 40, the percolation thresholds of 2D and 3D porous media decrease to 38.38% and 8.65%, respectively. Therefore, the pore connectivity of porous media is determined by the porosity and the pore distribution characteristics, whereas the pore connectivity of porous media can be misjudged if only porosity is taken into account.

The influence of membrane charge and porosity upon fouling and cleaning during the ultrafiltration of orange juice

The ultrafiltration of orange juice has been performed to separate phytosterols from proteins. Commercial regenerated cellulose acetate (RCA) ultrafiltration membranes of different molecular weight cut offs (MWCOs) of 10 kDa, 30 kDa and 100 kDa were fouled with orange juice and cleaned with Ultrasil 11 over two operational cycles. Fouling and cleaning mechanisms were investigated by using surface zeta potential, Brunauer-Emmet-Teller (BET) analysis and Fourier transform infrared (FTIR) analysis. The RCA conditioned membranes displayed zeta potential values of −0.2 to −31.5 mV. Fouling caused RCA membranes to have a greater magnitude of negative surface charge and cleaning restored the membrane surface charges close to its pristine state. Fouling increased both the total surface area and the total pore volume of all membranes. The total surface area and total pore volume for RCA 100 kDa after fouling increased by 102% and 185%, respectively. Pore area and volume distributions revealed that the porosities were returned close to the original level after cleaning. The recovery flux ratios of RCA 10, RCA 30 and RCA 100 decreased after fouling by 27%, 6% and 10% respectively; and changes were 25%, 9% and 1% respectively after cleaning. The charge of membrane surfaces after two operational cycles and the IR intensity of RCA membrane deposits, varied with MWCO such that RCA 30 > RCA 100 > RCA 10. Ultrafiltration using RCA 10 kDa membrane displayed the best separation efficiency, with 32 ± 4% rejection of phytosterols. and 96 ± 1% rejection of proteins. Changes in membrane surface charge and porosity have been found to affect the RCA membrane performance due to fouling and cleaning during the isolation of phytosterols from orange juice.

Three-dimensional pore characteristics and permeability properties of calcareous sand with different particle sizes

Calcareous sand is often used for island reef filling. The permeability of calcareous sand is a key parameter used to determine the consolidation time and the storage of fresh water during the construction of calcareous sand foundation. Pore structure characteristics are the key factors affecting permeability. In this study, X-ray computed tomography (CT) combined with pore network modeling were used to study the pore characteristics and permeability properties of calcareous sand with different particle sizes. The results show that the number and volume of pores in calcareous sand samples increase with increasing particle size. The pore volume distribution is uneven, and the pore shape does not change significantly with particle size. The permeability of calcareous sand increases with increasing particle size. The number of pores and the pore distribution are the key factors determining the permeability of calcareous sand with different particle sizes. When the particle size is larger than 1.45 mm, the presence of internal pores has a greater impact on the total number of pores and the permeability.

Elimination of ochratoxin A from white and red wines: Critical characteristics of activated carbons and impact on wine quality

Ochratoxin A (OTA) is a mycotoxin frequently found in wines, with an allowed maximum limit of 2.0 μg/L. To optimise OTA removal from white and red wines at high levels (10.0 μg/L) using activated carbons (ACs) different commercial deodorising ACs were tested. OTA elimination from white wines was less dependent on ACs characteristics, with 100% removal with all but one AC with the lowest total pore volume. For red wines, only one of the ACs with higher abundance of mesopores was successful in completely removing OTA. This decrease in performance was due to the competition of anthocyanins for ACs mesopores. ACs treatment impacted positively on white wine chromatic characteristics, decreasing the yellowness-brownish colour but for the red wine it was observed a higher but limited impact (maximum 24% decrease) on wine colour. ACs pore volume distribution, with pore sizes in the range 42.6–55.9 Å and 125.6–137.4 Å were important for efficient OTA removal. These results will allow the rational design of ACs with pore volume characteristics for OTA elimination with less impact on wine colour. Therefore, it was shown for the first time that AC with appropriate pore size distribution can remove completely OTA from white and also red wines.

Does high sulphur coal have the potential to produce high performance - low cost supercapacitors?

The heteroatom (S, N) content of the electrode material influences supercapacitor performance. Coals, which are abundant in nature, have different heteroatom contents. Activated carbon materials were synthesised from two different demineralised coal with low and high sulphur contents using chemical activation method. The samples are characterised in terms of total surface area, pore volume and size distribution, elemental, Fourier Transform Infrared (FTIR) Spectroscopy, X-ray Photo-electron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-Ray Diffraction (XRD) analyses. The total surface areas of the samples are 934 and 1869 m2g−1. While the sulphur contents of the raw coals are 12.35 % and 0.47 %, the sulphur content of the activated carbons produced from these raw materials are 3.5 % and undetectable. Supercapacitor performance is tested by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Galvanostatic Charge-Discharge (GCD) techniques. The analysis shows specific capacitances (Ccell, two-electrode cell) of 124.9 F.g−1 and 65.1 F.g−1 at 1 A.g−1 current density for the activated carbons produced from low and high sulphur contents, respectively. The tests show that demineralised coal with a high natural sulphur content is an ideal raw material for producing high value added activated carbon for supercapacitors.

Experimental characterization of cyclopentane adsorption/desorption in microporous activated carbons

In this work, the adsorption of cyclopentane (CP) is investigated and characterized on four activated carbons (ACs) of complementary textural properties by combining characterization (pore volume, pore and particle size distributions), adsorption/desorption isotherms of CP and adsorption enthalpy measurements. On the one hand, the adsorption/desorption isotherms measured with a magnetic suspension balance have shown that between nearly 30% to 50% of CP adsorbed at saturation remains trapped in the ACs even after prolonged evacuation under primary vacuum. On the other hand, calorimetric/manometric measurements have evidenced that high-energy adsorption occurs at the lowest CP-loadings. Gas porosimetry before and after CP adsorption/desorption has made it possible to identify that the pore size distribution is the key parameter that controls cyclopentane trapping and that micropores smaller than 1.1 nm are responsible for hardly-reversible CP adsorption. Coupling of TGA with gas porosimetry has shown that temperatures must be higher than 550 K to remove CP trapped in the ultramicroporosity.

Ultrahigh-Resolution 3D Imaging for Quantifying the Pore Nanostructure of Shale and Predicting Gas Transport

The pore and fracture microstructures are key to understanding gas flow in shales. The experimental determination of these microstructures is dependent on the measurement technique employed and its resolution. High-resolution three-dimensional imaging techniques coupled with image analysis and numerical simulations have been employed to characterize the petrophysical properties of shale samples. In this work, our particular focus is on using the Nano-CT and focused ion beam scanning electron microscopy (FIB-SEM) techniques at the same location in a shale rock sample to investigate the effect of their different resolutions and fields of view on the resulting imaged nanopore structure, as well as to determine any differences in the consequent measurements of the shale petrophysical properties. These petrophysical properties include porosity, permeability, pore volume and size distribution, the pore aspect ratio, the surface area to volume, and pore connectivity. The reconstructed matrix, kerogen, and pore space volumes from each approach showed significant scale-dependent differences in the microstructure. The shale sample displayed a high kerogen content with high connectivity. Porosity from the reconstructed shale volumes was observed to be 0.43 and 0.7% for FIB-SEM and Nano-CT approaches, respectively. The pore volume, size, surface area to volume ratio, and two orthogonal pore aspect ratio distributions have also been determined from the reconstructed image data by three-dimensional (3D) image analysis. These data show that voids within the rock are oblate at all scales. Permeabilities have been calculated from both the FIB-SEM and Nano-CT images and fall in the range of 2.55–9.92 nD. A simulation has also been produced based on the permeability calculation and parameters from the image analysis. The results of the simulation show connectivity in the x-, y-, and z-directions for both the FIB-SEM and Nano-CT images, with very low connectivity in the x-direction but higher connectivity in the y- and z-directions.

Adsorbent selection for pesticides removal from drinking water

ABSTRACT Pesticides present in water resources can cause adverse health effects even in low concentrations, due to their bio-accumulative character. Therefore, the challenge for drinking water production increases, due to the limitations of conventional water treatment technologies in the removal of small molecular weight dissolved compounds. This work aimed to provide technical and scientific support for the selection of pulverized activated carbon – PACs, granular activated carbon – GACs, and carbon nanotubes – CNT concerning atrazine – ATZ, simazine – SMZ, and diuron – DIU adsorption for application in water treatment plants, considering two forms of application commercial product – CP and analytical standard – SD. These forms of application were tested aiming to verify the influence of the purity of the products used in experiments on the adsorption efficiency. It was possible to verify the adsorption efficiencies were not guided only by the characteristics of the adsorptive materials used, and that the selection should not be carried out only based on the, specific superficial area – BET size and distribution of specific pore volume. The isotherms demonstrated that the parameter Kf associated with the results of the selection experiment can be considered an alternative technical tool of simple application and sufficient for this purpose. Also, the capacity of activated carbons – ACs and nanomaterials – NMs were affected by the application of the compounds, highlighting the importance of using commercial product – CP in scientific research and technical investigations. Hightlights The pesticides efficiency removal was affected due to the forms of application, SD and CP; The parameters IN and MBI were not decisive in the selection of the activated carbon; The main adsorption mechanism in all the materials was chemical; GAC was the most efficient adsorbent in the removal of the pesticides; An adequate adsorbent selection is crucial for satisfactory removal of pesticides in water.

Exploration of the Optimum Rice Husk Biochar for Atrazine and 2,4-D Removal: Different Pyrolysis and Modification Conditions

In this study, the best RHB (rice husk biochar) was investigated through the effect of pyrolysis synthesis processes and modifications. Five biochars were synthesized from rice husk waste materials at different pyrolysis temperatures (400 to 600 °C) in oxygen-limited conditions. The biochars were modified by acids to remove minerals on the surface area. The characteristics of the biochars were determined including surface morphology, specific surface area, and functional groups. The herbicide adsorption was accomplished by the batch equilibration method. The result indicated that the biochar that synthesized 500 °C for 6 h had the highest maximum adsorption capacity. The optimum RHB was biochar modified with HF acid. The optimum biochar had less or no minerals and it achieved abundant functional groups on the surface areas. The pore volume distributions in pore sizes of micropores and narrow mesopores played an important role to perform the uptake of the herbicides, they were in the range of 7.90 % and 59.26 %, respectively. The high-efficiency removals of atrazine and 2,4-D by optimum biochar were 82.70 % and 95.10 %, respectively. The rice husk biochar is a suitable adsorbent to remove herbicides from the aqueous environment. Keywords: Adsorbent; Adsorption; Atrazine; Biochar; 2,4-D. DOI 10.35180/gse-2020-0042

Simulation Studies of Random Sequential Adsorption (RSA) of Mixture of Two-Component Circular Discs

We study Random Sequential Adsorption (RSA) of mixture of two-component circular discs on a two-dimensional continuum substrate by computer simulation for different values of radius ratio $${r}_{A}/{r}_{B}$$ , $$({r}_{A}<{r}_{B})$$ , and relative rate constant $$k = {k}_{A}/{k}_{B}$$ between the discs. For smaller values of radius ratio and all values of relative rate constant between the discs, the approach of instantaneous surface coverage $$\theta (t)$$ to the jammed state surface coverage $$\theta (\infty )$$ of larger and smaller discs, is found to obey a power law behavior $$\theta \left(\infty \right)-\theta (t)\sim {t}^{-p}$$ , separately. For larger values of radius ratio and relative rate constant $$k$$ , the approach is found to obey same power law. Total surface coverage of binary mixture $$\theta (\infty )$$ for all the cases is found always greater than 54.7%, the one component jamming limit. Also, it is found that for a given radius ratio $${r}_{A}/{r}_{B}$$ , there is an optimum value of relative rate constant $$k = {k}_{A}/{k}_{B}$$ for which jamming coverage $$\theta (\infty )$$ is maximum. Also, our study shows that in case of adsorption of a binary mixture of circular discs of a given radius ratio $${r}_{A}/{r}_{B}$$ , relative rate constant $$k$$ can be fixed in order to get maximum or desired surface coverage. Microstructural properties of the coverings formed by RSA of binary mixture of circular discs are studied by analyzing radial distribution function and volume distribution of pores.

Microstructural changes and mass transport in cement-based materials: A modeling approach

A generic modeling framework is presented to relate microstructural changes, i.e. changes in the pore volume distribution and phase assemblage, and mass transport in cement-based materials. The modeling framework accounts for mass transport and chemical equilibrium between ions in the pore solution and solid hydrates by means of an extended version of the Poisson-Nernst-Planck equation, in which the chemical equilibrium is solved by the external geochemical code IPHREEQC. Results of numerical studies concerning carbonation and leaching of a cement-based material indicate significant changes in mass transport properties due to chemical reactions leading to alterations in the microstructure. The resulting highly non-linear (both spatial and temporal) microstructural changes are thereby depending on the exposure and indicate that interactions between chemical reactions, pore structure changes, and mass transport have to be accounted for as a whole.

Production Conditions of Nanoporous Ceramics Based on Mullite

A technology for producing nanoporous ceramics based on mullite (3Al2O3 ⋅ 2SiO2) is developed. The mechanochemical activation of oxides involved in the synthesis of mullite (γ-Al2O3 and amorphous SiO2) makes it possible to obtain single-phase 3Al2O3 ⋅ 2SiO2 and to reduce its sintering temperature to 1300°С. The effect of the pressing pressure and the amount of pore-forming additive (ammonium carbonate) on the value of open porosity, pore volume, and pore size distribution in sintered ceramics 3Al2O3 ⋅ 2SiO2 is established. Mullite nanoceramics with open porosity of 42–47%, pore size <200 nm, and compressive strength 50–65 MPa is obtained.

Assessment of activated carbon fibers from commercial Kevlar® as nanostructured material for gas storage: Effect of activation procedure and adsorption of CO2 and CH4

Carbon-based nanostructures are considered promising materials for gas storage thanks to robust structure, tunable porosity, lightweight, high thermal/chemical stability and easy production. This study reports the development of activated carbon fibers prepared from commercial Kevlar® through an innovative pyrolysis method, consisting of carbonization in inert ambient and subsequent physical activation in oxidizing atmosphere, using a unique apparatus. Varying three key parameters, time (range 60−240 min), temperature (range 1023−1123 K) and gas-flow (0.3/0.9/1.2 Nl/min of CO2), the correlation between the activation procedure and the resulting samples structure was evaluated. The best results in terms of microporosity and gas adsorption properties have been obtained by reducing the activation times of the material. Furthermore, the purpose has been to optimize the characteristics in terms of Specific Surface Area, Total Pore Volume and optimal Pore Size Distribution. The method made it possible to develop an adsorbent material with a high fraction of micropores up to 94 % of the total pore volume, straddling the supermicroporosity (0.7−2 nm) and ultramicroporosity (<0.7 nm) region. Such textural properties have resulted in high gases storage capacities, tested at different temperatures (280, 298, 314 K), with maximum uptake of 46 wt% for CO2 and almost 10 wt% for CH4. All produced samples were characterized by helium picnometry to estimate skeletal density, Scanning Electron Microscopy to obtain morphological information, porosimetry to know structural properties. The adsorption behaviour was tested using a Sievert-type apparatus in the pressure range of 0−15 bar for CO2 and 0−40 bar for CH4.