Range Of Pore Sizes Research Articles

Critical pore size for micropore filling in coal samples with different rank coals.

The objectives of this study were to explore the occurrence and migration of coalbed methane in coals of different ranks and reveal the microscopic reservoir space and the mechanism of coalbed methane. To meet these objectives, this study selected six coal samples of different coal ranks for low-pressure N2 adsorption experiments, explored the critical pore filling characteristics of packed N2 molecules in the coals, and analyzed the low-pressure N2 adsorption/desorption experimental isotherms using the DFT method and DA equation based on the micropore filling theory. Finally, the critical filling pressure and pore size range for micropore filling were determined, and the analysis results were verified by combining the Langmuir, DA, and BET equations. The results showed that, from low to high coal rank, the N2 adsorption/desorption isotherms of the coal samples transition from type Ⅱ to type Ⅰ. The proportion of N2 molecules in low-rank coals in the form of micropore filling and monolayer adsorption was higher than that in high-rank coals. The critical pressure and critical pore size for micropore filling exhibited U-shaped correlations with the coal rank. Low-rank coals (lignite and long flame coal) were gradually filled in the relative pressure range P/P0 ≈ 1E-4–0.03, and medium- and high-rank coals (gas coal, 1/3 coking coal, lean coal, and anthracite) were filled in the relative pressure range P/P0 ≈ 1E-4–0.01; the corresponding critical pore size ranges were 1.7–2.19 and 1.61–2.00 nm, respectively.

Fractal Characteristics of the Pore Structure of Coral Powder–Cement Slurry under Different Fractal Models

In this study, coral powder with different contents and levels of fineness were incorporated into cement; then, the pore structure of a coral powder–cement slurry was measured using the MIP test at days 3 days and 28, respectively. Neimark’s model, Ji’s model, and Pfeifer and Avnir’s model were also used to analyze the fractal characteristics of the coral powder–cement slurry. The results show that the coral powder–cement slurry has multifractal characteristics when using Neimark’s model, and the entire pore size range of the cement slurry can be divided into three parts: Region I (1–200 μm), Region II (70 nm–4 μm), and Region III (5–500 nm). The pore surface fractal dimension of both Regions I and III is less than 3, while that of Region II is greater than 3. This indicates that Regions I and III have obvious fractal characteristics, which Region II does not. Meanwhile, the pore surface fractal dimension of Region I is positively correlated with hydration age, while the pore surface fractal dimension of Region III is less affected by hydration age and coral powder contents. Ji’s model reveals that coral powder–cement slurry also has multifractal characteristics, but the entire pore size range of the cement slurry can be divided into two parts: Region I (5.482 nm–500 m) and Region II (120 nm–370 μm). The pore volume fractal dimension of Region I is greater than 2 and less than 2.5, while that of Region II is greater than 2.9 and less than 3. Therefore, both Regions I and II have fractal characteristics. In addition, the coral powder admixture, fineness, and age have large effects on the pore volume fractal dimension and pore size range of Region II. Pfeifer and Avnir’s model reveals that the entire pore size range of cement slurry can also be divided into Region I (5.482–600 nm), Region II (120 nm–10 μm), and Region III (5–365 μm), and that the pore surface fractal dimension of both Regions I and III is less than 3, while that of Region II is greater than 3. This indicates that Regions I and III have fractal characteristics, while Region II does not have fractal characteristics.

X-ray speckle-based dark-field imaging of water transport in porous ceramics

The evaluation of liquid transport through porous ceramics are of high importance in numerous applications of these materials, ranging from chemical and physical filters to biomaterials. We present a proof-of-concept of the capability of speckle-based Xray dark-field imaging (XDFI) for studying the water transport through porous materials with high sensitivity and sub-pixel resolution in a laboratory. Speckle-based imaging (SBI) takes advantage of a simple and flexible setup, with only an additional and inexpensive textured mask, to provide complementary multi-contrast images. Porous ceramic samples with different pore size ranges were imaged in dry and different pure water-saturated states, via an X-ray speckle-tracking setup. The retrieved darkfield images revealed a high sensitivity to (1) the pore size range and to (2) the local water saturation degree. Independently of the pore size range, the dark-field signal decreased upon water saturation. Compared with previously reported laboratory-scale XDFI results for water transport through porous materials, the speckle-tracking approach allows achieving higher temporal and spatial resolutions, thus broadening the range of (water) transport processes which can be investigated without using any contrast agent.

METHANOL MASS VARIATION OF MESOPOROUS SILICA SYNTHESIS USING RICINOLEIC METHYL ESTER AS A TEMPLATE

This study aims to synthesize mesoporous silica using ricinoleic methyl ester as a template with the variation of methanol mass. Mesoporous silica was synthesized using ricinoleic methyl ester as a template, 3-aminopropyltrimethoxysilane as a structural directing agent, and tetraethyl orthosilicate (TEOS) as a source of silica. The novelty of this study lies in the use of ricinoleic methyl ester as a template. The reaction conditions were varied by varying the amount of methanol without adding hydrochloric acid 0.1M. The yield of mesoporous silica in samples named MSME A, MSME B, and MSME C was 1.63 g, 1.70 g, and 1.80 g. It shows that adding methanol mass affects the yield of mesoporous silica. Fourier-transform infrared spectroscopy (FTIR) analysis revealed that all silica products formed Si-O-Si bonds between 1103 cm-1 and 1111 cm-1 due to asymmetric stretching vibration. All silica products have a diffractogram at 2θ between 10o and 30o, indicating amorphous. The scanning electron microscope (SEM) image demonstrates the mesoporous silica morphology as a mixture of spherical particles and multiple sheets, fused round particles, aggregated particles, and spreading spherical particles. The BET analysis reveals a homogeneous pore size distribution in the third and fourth treatments. Each is dominated by a pore size range of 8.43 nm to 8.50 nm.

Isoporous Polyvinylidene Fluoride Membranes with Selective Skin Layers via a Thermal-Vapor Assisted Phase Separation Method for Industrial Purification Applications.

The membrane filtration process is the most widely used purification process in various industries due to its high separation efficiency, process simplicity, and low cost. Although there is a wide range of membrane products with diverse materials and pore sizes on the market, there is a technological gap between microfiltration and ultrafiltration membranes. Here we developed highly porous polyvinylidene fluoride (PVDF) membranes with a selective skin layer with a pore size range of 20 to 80 nm by using a thermal-vapor assisted phase separation method. Porous and bi-continuous sublayers were generated from spinodal decomposition induced by cooling. The overall membrane structure and pore size changed with the dope composition, while the pore size and thickness of the selective skin layer were effectively controlled by water vapor exposure. The excellent nanoparticle removal efficiencies of the prepared PVDF membranes were confirmed, indicating their potential application in high-level purification processes to remove small trace organic or inorganic impurities from various industrial fluids.

Experimental study on compressive strength and frost resistance of steam cured concrete with mineral admixtures

The study of frost resistance and mechanical properties of steam cured concrete is helpful to understand the state of precast concrete elements in a complex environment. In this paper, the compressive strength of concrete under 10 working conditions, such as standard cured system, steam cured system, no mineral admixtures, single ground granulated blast furnace slag (GGBS) and fly ash (FA) mixed with GGBS, was tested at the age of 180d. It is found that the compressive strength of concrete under standard cured system is 4.71% to 18.46% higher than that under steam cured system, although steam cured improves the strength at the initial stage. The addition of FA and GGBS can make up 14% to 16% strength defects caused by steam cured system. The compressive strength of steam cured concrete (ZF40℃) is the highest when the steam cured temperature is 40℃ and the mixture ratio of FA and GGBS is 2:3. On this basis, the frost resistance of ZF40℃ specimens was studied. The results showed that the surface degradation degree of steam cured concrete gradually deepened with the increase of freeze–thaw (F-T) cycles, and the extracted surface roughness ranged from 0.066 ∼ 0.505 mm. The relative dynamic elastic modulus and mass loss rate decreased with the increase of F-T cycles, and the maximum loss rate were 69.4% and 1.41%, respectively. In addition, the compressive strength test, acoustic emission (AE) signal monitoring and acquisition of pore structure characteristics were carried out to understand the mechanical properties of steam cured concrete under F-T cycles conditions. The results show that the compressive strength decreases with the increase of F-T cycles, and the strength loss rate is within 10% per 50 cycles. The overall activity of AE signal decreases with the increase of F-T cycles, andthe damage form gradually changes from the initial tensile damage to the later shear damage. Porosity and pore size range basically increase with the increase of F-T cycles. Pore deterioration is the main reason for the decrease of compressive strength of steam cured concrete under F-T environment.

Increasing the Diameter of Vertically Aligned, Hexagonally Ordered Pores in Mesoporous Silica Thin Films.

The variation in pore size in mesoporous films produced by electrochemically assisted self-assembly (EASA) with the surfactant chain length is described. EASA produces a hexagonal array of pores perpendicular to the substrate surface by using an applied potential to organize cationic surfactants and the resultant current to drive condensation in a silica sol. Here, we show that a range of pore sizes between 2 and 5 nm in diameter is available with surfactants of the form [Me3NCnH2n+1]Br, with alkyl chain lengths between C14 and C24. The film quality, pore order, pore size, and pore accessibility are probed with a range of techniques.

3D biocompatible bone engineering foams with tunable mechanical properties and porous structures

AbstractLarge bone defects due to accidental injuries and fractures as well as the mismatch between the implant material and the defect site are major problems in biomedicine. Bone tissue engineering offers a solution to this problem. In this paper, a series of three‐dimensional porous composite scaffolds with shape memory were prepared using polycaprolactone and polytetrahydrofuran as soft segment materials, hexamethylene diisocyanate as hard segment materials and amorphous calcium phosphate/calcium citrate (CAP) as inorganic fillers. The scaffolds have tunable mechanical properties, melt temperature, surface wettability, a pore size range of 100–800 μm and a high degree of connectivity. In vitro mineralization showed good mineral deposition and energy dispersion spectrometer displayed uniform distribution of Ca and P elements on the surface. The composite scaffold exhibited good shape memory properties at 37°C. The shape fixation rate (Rf) and shape recovery rate (Rr) were maintained at 94.1% and 94.4% after five compression cycles. The resulting scaffold promoted MG63 cell proliferation to some extent. The scaffold is expected to be used clinically for the treatment of large bone defects.

Pore structure controls stability and molecular flux in engineered protein cages.

Protein cages are a common architectural motif used by living organisms to compartmentalize and control biochemical reactions. While engineered protein cages have featured in the construction of nanoreactors and synthetic organelles, relatively little is known about the underlying molecular parameters that govern stability and flux through their pores. In this work, we systematically designed 24 variants of the Thermotoga maritima encapsulin cage, featuring pores of different sizes and charges. Twelve pore variants were successfully assembled and purified, including eight designs with exceptional thermal stability. While negatively charged mutations were better tolerated, we were able to form stable assemblies covering a full range of pore sizes and charges, as observed in seven new cryo-EM structures at 2.5- to 3.6-Å resolution. Molecular dynamics simulations and stopped-flow experiments revealed the importance of considering both pore size and charge, together with flexibility and rate-determining steps, when designing protein cages for controlling molecular flux.

Size‐Controlled Nanosculpture of Cylindrical Pores across Multilayer Graphene via Photocatalytic Perforation

AbstractOne of the bottlenecks in realizing the potential of nanoporous graphene assemblies is the difficulty of engineering narrow pores and high surface density distributions, with a nanometer resolution across multilayer graphene assemblies using scalable approaches. Here, the authors develop a photocatalyzed perforation protocol to incorporate nanopores across modified graphene assemblies via localizing the oxidation during the photo‐excitation process between photo‐initiators and graphitic assemblies under the ultraviolet–visible stimuli. Nanopores are engineered across the graphene nanostructures with a pore size range varying from 20 to 100 nm depending on the irradiation duration, as well as tunable densities of 101–103 pores/µm2 on the same order of the loaded nanocatalysts to the graphene surfaces. By fine‐tuning the graphene chemistry and the physical dimension of photo‐initiators, as well as their concentrations across graphitic planes used during the perforation, the diameter, and the density distributions of generated nanopores across graphene, can be rationally confined, avoiding merging between pores during the nanopore formation. These porosity parameters engineered across graphene nanosieves are in the same order obtained by other nanolithographic techniques. Plus, this sustainable route may boost the potential of porous graphene assemblies in energy‐efficient nanotechnologies based on separation and catalytic processes.

Biomimetic PLGA/Strontium-Zinc Nano Hydroxyapatite Composite Scaffolds for Bone Regeneration.

Synthetic bone graft substitutes have attracted increasing attention in tissue engineering. This study aimed to fabricate a novel, bioactive, porous scaffold that can be used as a bone substitute. Strontium and zinc doped nano-hydroxyapatite (Sr/Zn n-HAp) were synthesized by a water-based sol-gel technique. Sr/Zn n-HAp and poly (lactide-co-glycolide) (PLGA) were used to fabricate composite scaffolds by supercritical carbon dioxide technique. FTIR, XRD, TEM, SEM, and TGA were used to characterize Sr/Zn n-HAp and the composite scaffolds. The synthesized scaffolds were adequately porous with an average pore size range between 189 to 406 µm. The scaffolds demonstrated bioactive behavior by forming crystals when immersed in the simulated body fluid. The scaffolds after immersing in Tris/HCl buffer increased the pH value of the medium, establishing their favorable biodegradable behavior. ICP-MS study for the scaffolds detected the presence of Sr, Ca, and Zn ions in the SBF within the first week, which would augment osseointegration if implanted in the body. nHAp and their composites (PLGA-nHAp) showed ultimate compressive strength ranging between 0.4–19.8 MPa. A 2.5% Sr/Zn substituted nHAp-PLGA composite showed a compressive behavior resembling that of cancellous bone indicating it as a good candidate for cancellous bone substitute.

Analysis of Three-Dimensional Cell Migration in Dopamine-Modified Poly(aspartic acid)-Based Hydrogels.

Several types of promising cell-based therapies for tissue regeneration have been developing worldwide. However, for successful therapeutical application of cells in this field, appropriate scaffolds are also required. Recently, the research for suitable scaffolds has been focusing on polymer hydrogels due to their similarity to the extracellular matrix. The main limitation regarding amino acid-based hydrogels is their difficult and expensive preparation, which can be avoided by using poly(aspartamide) (PASP)-based hydrogels. PASP-based materials can be chemically modified with various bioactive molecules for the final application purpose. In this study, dopamine containing PASP-based scaffolds is investigated, since dopamine influences several cell biological processes, such as adhesion, migration, proliferation, and differentiation, according to the literature. Periodontal ligament cells (PDLCs) of neuroectodermal origin and SH-SY5Y neuroblastoma cell line were used for the in vitro experiments. The chemical structure of the polymers and hydrogels was proved by 1H-NMR and FTIR spectroscopy. Scanning electron microscopical (SEM) images confirmed the suitable pore size range of the hydrogels for cell migration. Cell viability assay was carried out according to a standardized protocol using the WST-1 reagent. To visualize three-dimensional cell distribution in the hydrogel matrix, two-photon microscopy was used. According to our results, dopamine containing PASP gels can facilitate vertical cell penetration from the top of the hydrogel in the depth of around 4 cell layers (~150 μm). To quantify these observations, a detailed image analysis process was developed and firstly introduced in this paper.

Pores integrated fractal (PIF) analysis on transportation in porous media considering spatial distribution of pores and genuine tortuosity

A pores integrated fractal model is established to represent the microscopic structures of porous media in consideration of the spatial distribution of pores and the genuine tortuosity in various transportation processes. Transport equations are obtained based on the PIF model, providing high precision for predicting the effective thermal conductivity, the permeability and diffusion coefficient in porous materials. Spatial distributions of pores in realistic samples are acquired, based on which the influence of the equivalent pore distributions is specifically analyzed in the study. In the premise of the same porosity, broader range of pore size, dominant pores in dozens of micron or bimodal distribution of pores are crucial factors that influence the heat conduction and permeation in porous media. It is noted that the PIF model has significant values in the design of porous structure with improved transportation characteristics and in the accurate prediction of vital parameters in complex porous media.

NMR Analysis Method of Gas Flow Pattern in the Process of Shale Gas Depletion Development

Shale gas reservoirs have pores of various sizes, in which gas flows in different patterns. The coexistence of multiple gas flow patterns is common. In order to quantitatively characterize the flow pattern in the process of shale gas depletion development, a physical simulation experiment of shale gas depletion development was designed, and a high-pressure on-line NMR analysis method of gas flow pattern in this process was proposed. The signal amplitudes of methane in pores of various sizes at different pressure levels were calculated according to the conversion relationship between the NMR T 2 relaxation time and pore radius, and then, the flow patterns of methane in pores of various sizes under different pore pressure conditions were analyzed as per the flow pattern determination criteria. It is found that there are three flow patterns in the process of shale gas depletion development, i.e., continuous medium flow, slip flow, and transitional flow, which account for 73.5%, 25.8%, and 0.7% of total gas flow, respectively. When the pore pressure is high, the continuous medium flow is dominant. With the gas production in shale reservoir, the pore pressure decreases, the Knudsen number increases, and the pore size range of slip flow zone and transitional flow zone expands. When the reservoir pressure is higher than the critical desorption pressure, the adsorbed gas is not desorbed intensively, and the produced gas is mainly free gas. When the reservoir pressure is lower than the critical desorption pressure, the adsorbed gas is gradually desorbed, and the proportion of desorbed gas in the produced gas gradually increases.

Brute force determination of the optimum pore sizes for CO2 uptake in turbostratic carbons

The relationship between porosity within a given pore size range, and uptake of CO2 as a function of pressure.

Cellular responses to nanoscale substrate topography of TiO2 nanotube arrays: cell morphology and adhesion.

Nanotopographical features can be beneficial in augmenting cell functions and increasing osteogenic potential. However, the relationships between surface topographies and biological responses are difficult to establish due to the difficulty in controlling the surface topographical features at a low-nanometre scale. Herein, we report the fabrication of well-defined controllable titanium dioxide (TiO2) nanotube arrays with a wide range of pore sizes, 30-175 nm in diameter, and use of the electrochemical anodization method to assess the effect of surface nanotopographies on cell morphology and adhesion. The results show that TiO2 nanotube arrays with pore sizes of 30 and 80 nm allowed for cell spreading of bone marrow-derived mesenchymal stem cells with increased cell area coverage. Additionally, cell adhesion was significantly enhanced by controlled nanotopographies of TiO2 nanotube arrays with 80 nm pore size. Our results demonstrate that surface modification at the nano-scale level with size tunability under controlled chemical/physical properties and culture conditions can greatly impact cell responses. These findings point to a new direction of material design for bone-tissue engineering in orthopaedic applications.

Effect of self-diverting acid viscosity and the chemical structure of coal under different acid environment

In order to solve the poor water infusion problem for low permeability coal seams, this paper studied the self-diverting acid to uniformly distribute acid. The results show that massive Ca2+ generated by the reaction between HCl and calcite can enhance the crosslinking of micelles. With the increase of HCl concentration, the viscosity increased and then decreased, which could be divided into “low viscosity zone” (0.1%–2%), “viscosity rapid increase zone” (2%–5%) and “viscosity decrease zone” (5%–15%). After treated with self-diverting acid, the fracture width and connectivity of coal was increased. Massive clay minerals were dissolved, the distribution range of pore size and pore volume gradually increased, and a large number of pores caused by corrosion appeared. Due to the influence of viscosity, the wettability of self-diverting acid for the coal was gradually reduced during infusion process. However, compared with distilled water, the overall wettability of coal still increased by 6.91%.

3D Printed SiOC(N) Ceramic Scaffolds for Bone Tissue Regeneration: Improved Osteogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells.

Bone tissue engineering has developed significantly in recent years as there has been increasing demand for bone substitutes due to trauma, cancer, arthritis, and infections. The scaffolds for bone regeneration need to be mechanically stable and have a 3D architecture with interconnected pores. With the advances in additive manufacturing technology, these requirements can be fulfilled by 3D printing scaffolds with controlled geometry and porosity using a low-cost multistep process. The scaffolds, however, must also be bioactive to promote the environment for the cells to regenerate into bone tissue. To determine if a low-cost 3D printing method for bespoke SiOC(N) porous structures can regenerate bone, these structures were tested for osteointegration potential by using human mesenchymal stem cells (hMSCs). This includes checking the general biocompatibilities under the osteogenic differentiation environment (cell proliferation and metabolism). Moreover, cell morphology was observed by confocal microscopy, and gene expressions on typical osteogenic markers at different stages for bone formation were determined by real-time PCR. The results of the study showed the pore size of the scaffolds had a significant impact on differentiation. A certain range of pore size could stimulate osteogenic differentiation, thus promoting bone regrowth and regeneration.

From Feather to Adsorbent: Keratin Extraction, Chemical Modification, and Fe(III) Removal from Aqueous Solution

In this work, feather keratin was extracted from the waste feather of chicken via alkyd pretreatment and reduction method, the extraction rate is above 85%. The molecular weight and aggregation morphology of feather keratin in an aqueous environment were characterized by 18-angle laser light scattering gel permeation chromatography and field emission transmission electron microscopy. The relationship between the structure and properties of feather keratin is discussed. The 1-(3-dimethylaminopropyl) -3-ethylcarbondiimide hydrochloride and N-hydroxysuccinimide were used as activation system and cross-linkage. The gallic acid was used as modification reagent and was bonded to feather keratin chains; meanwhile, feather keratin chains were cross-linked through covalent bonds obtained the novel adsorbent (named as GA-FK gel). The GA-FK gel was investigated by IR, SEM, TGA, XRD, and BET methods. The results indicated that GA molecules successfully bonded to feather keratin chains and cross-linked between feather keratin chains. The GA-FK gel was found to have a three-dimensional network structure with abundant mesopores. Its pore size range is 1.8~90 nm; average pore size is 19.6 nm. Its specific surface area is 7.17 m2·g−1. In addition, GA-FK gel was applied to remove Fe(III) in water. The maximum adsorption capacity was 319.0 mg·g−1. The adsorption process of GA-FK gel to Fe(III) presents a typical two-stage pattern accompanied with swelling. The adsorption kinetics of GA-FK gel to Fe(III) follows the quasi-second-order model, the adsorption isotherm follows the Freundlich model. Therefore, the adsorption mechanism is non-specific adsorption.

Chemical Modification Effect of Compound Solutions of Surfactants with Acetic Acid on Coal Pores.

Coal seam pores are the major places for coalbed methane storage, diffusion, and seepage, and changes in the pore structure cause changes in the porosity. The porosity of coal seams can be effectively improved by applying strongly corrosive and oxidative chemical reagents to coal seam pores, but these reagents may pose threats to coal workers, corrode mining equipment, and pollute the environment. In this study, coal samples were treated with solutions compounded by acetic acid and anionic, cationic, and non-ionic surfactants. The variations of pores in coal samples after the compound modification of surfactants and acetic acid were investigated. Experimental methods of SEM, MIP, LTNA, PAC, and FTIR and fractal theory are applied in this work. The results reveal that the compound modification of surfactants and acetic acid conduces to the transformation of pore shape and affects a wider pore size range. The anionic and cationic surfactants can increase the hydrophilicity and can promote the connection of larger pores. The non-ionic surfactant reduces the hydrophilicity and capillary effect yet increases the porosity. Thus, it promotes the connection of pores and makes the pore surface smooth and the pore structure simple. Comparing the three kinds of surfactants, non-ionic surfactants are more conducive to coal seam pore reconstruction.