Homogeneous Pore Research Articles

Damage quantification of archaeological pottery in Sheikh Hamad “Athribis” Sohag-Egypt

Abstract Many archaeological potteries in Sheikh Hamad (Athribis) Sohag, Egypt suffer from different processes, which led to many deterioration forms. Samples collected from Athribis were submitted to qualitative and quantitative measurements through using different techniques to evaluate their durability states. Significant information derived from these techniques prove that our materials are composed of Si, Al, Fe, Mg, K, Ca, Na and Cl as the main elements of Quartz Albite, Microcline, Calcite and Hemetite (main components of Nile clays) and Halite (main salt characterizes Egyptian land). In addition, SEM reveals that the samples are characterizes by cohesion of the granules, non homogeneous texture and different size pores in addition to degradation, dissolution features and cracks. Finally, it can be concluded that most of these artifacts are affected by two main aggressive mechanisms: their burial environment (before excavation) and aired environment (after excavation). These process that finally led to some aggressive deterioration forms.

Morphology of Aluminum Alloy Foams Produced with Dolomite via Partial Sintering of Precursors.

Highly expanded, low-cost aluminum-based foams were successfully produced via powder metallurgy using dolomite as foaming agent. Nickel additions (5–15 wt.%) were explored in order to reduce the temperature disparity between dolomite decomposition and the melting range of the metallic matrix. Specific Al–Ni compositions provide appropriate viscosities for effective encapsulation of CO2 gas released during dolomite decomposition. A partial sintering step of compacted precursors was introduced prior to foaming, which resulted in high porosity levels (~86%) and significant volume expansion (~250%) in the final product. The partial sintering technique was a key determining factor in obtaining stable, highly expanded cellular structures with homogeneous pores, averaging 3 mm in size and being morphologically comparable with ALPORASTM foams.

The influence of porosity on the release of water from perlite glass by thermal treatment

The water release from perlite from the three most important deposits in Central Europe was investigated with the aim to improve the understanding of the expansion process of perlites. Several attributes: water content, temperature, porosity, particle size, and mineralogical and chemical composition were evaluated. Detailed measurements of the water release by thermal treatment at a temperature range between 150 and 850 °C, and at various times from 1 min to 100 h were performed. The highest differences were observed between porous and dense perlites at 150 °C. Porosity and pore characterisation were performed by X-ray μ-computed tomography and N2-adsorption. The porosity of perlite with large pores and homogenous pores distribution was decreased and the porosity with heterogeneous distribution was able even increased after grinding. These findings were determined on three mutually perpendicular sections of 3D images of the three studied porous perlites and explain the highest water releasing from perlite with the lowest porosity among them. Slovak crude perlites include higher amount of loosely bound water (45–60% of H2Ot, released in temperature range 0–250 °C) and lower amount of strongly bound water (1–7% of H2Ot, released in temperature over 550 °C) in comparison with Hungarian and other world perlites (18–50%, respectively, 6–23% of H2Ot). Slovak crude perlites also contain higher ratio of K2O to Na2O (2–2.5) when compared to other world perlites (0.7–1.4). These can be important factors that cause discrepancies in the expansibility of perlites among Slovak and world perlites.

Electrospun microporous gelatin–polycaprolactone blend tubular scaffold as a potential vascular biomaterial

AbstractThe work reported involved the fabrication of an electrospun tubular conduit of a gelatin and polycaprolactone (PCL) blend as an adventitia‐equivalent construct. Gelatin was included as the matrix for increased biocompatibility with the addition of PCL for durability. This is contrary to most of the literature available for biomaterials based on blends of gelatin and PCL where PCL is the major matrix. The work includes the assiduous selection of key electrospinning parameters to obtain smooth bead‐free fibres with a narrow distribution of pore size and fibre diameter. Few reports elucidate the optimization of all electrospinning parameters to fabricate tubular conduits with a focus on obtaining homogeneous pores and fibres. This stepwise investigation would be unique for the fabrication of gelatin–PCL electrospun tubular constructs. The fabricated microfibrous gelatin–PCL constructs had pores of size ca 50–100 μm reportedly conducive for cell infiltration. The measured value of surface roughness of 57.99 ± 17.4 nm is reported to be favourable for protein adhesion and cell adhesion. The elastic modulus was observed to be similar to that of the tunica adventitia of the native artery. Preliminary in vitro and in vivo biocompatibility tests suggest safe applicability as a biomaterial. Minimal cytotoxicity was observed using MTT assay. Subcutaneous implantation of the scaffold demonstrated acute inflammation which decreased by day 15. The findings of this study could enable the fabrication of smooth bead‐free microfibrous gelatin–PCL tubular construct as viable biomaterial which can be included in a bilayer or a trilayer scaffold for vascular tissue engineering. © 2019 Society of Chemical Industry

Mechanically robust and flexible silk protein/polysaccharide composite sponges for wound dressing

The cutaneous tissue contains cellular protein and polysaccharide components which together maintain the functionality of the tissue. In this study, silk fibroin (SF) and konjac glucomannan (KGM) were physically crosslinked to form biocompatible protein/polysaccharide sponges with tunable mechanical properties for wound dressing application. The pore structure of sponges can be adjusted by changing blend ratio of SF/KGM, forming homogeneous interconnected pore structure. FTIR and Raman results revealed the intermolecular interaction between SF and KGM, suggesting the formation of interpenetrating polymer network after ethanol/ammonium hydroxide treatment. Raising KGM content significantly enhanced water-absorption, water-retention abilities, and compression strength of porous sponges. Especially, the composite sponges possessed a similar compressive modulus with native skin tissue, showing a matched flexibility for wound treatment. Moreover, the cell viability results based on human dermal fibroblast cells demonstrated that the sponge showed excellent biocompatibility for cell adhesion and proliferation. Therefore, due to the strong water-absorption capacity, moist environment, similar compressive modulus with skin tissue and excellent biocompatibility, the composite sponges have potential application in wound dressings.

Novel pore-filling membrane based on block sulfonated poly (ether sulphone) with enhanced proton conductivity and methanol resistance for direct methanol fuel cells

The problem remains unsolved in DMFCs applications that the increase in proton conductivity is usually caused the permeation of methanol. Herein, a novel kind of pore-filling membrane is investigated to meet this challenge. The porous substrate is fabricated from block poly (ether sulphone) with low degree of sulfonation, which form well-developed conductive channels owing to an aggregation of sulfonic acid groups, ensuring low methonal crossover and swelling ratio. The pore structures are achieved by a solution casting method which introduces alpha-cyclodextrin as the porogen. The resulting porous substrate possesses homogeneous opening pore structures. Then, the filling electrolyte, an organic-soluble tetrabutylammonium 4-vinylbenzene sulfonate, is used to fill the substrate and form a crosslinked network inside the pores to ensure high proton conductivity. The pore-filling membrane with block polymers shows higher proton conductivity (0.083 S cm−1 at 80 °C) than that prepared by random polymers (0.072 S cm−1 at 80 °C). Compared with Nafion 117, the composite membrane exhibits higher dimensional stability (6.6%) and methanol resistance (4.0 × 10−7 cm2 s−1). Furthermore, the pore-filling membrane outperforms Nafion 117 with an open circuit voltage of 0.61 V as well as a maximum power density of 46.8 mW/cm2 under 10 M methanol condition.

In vitro and in vivo performance of a propolis-coated polyurethane wound dressing with high porosity and antibacterial efficacy.

Wound dressings with antimicrobial and wound healing accelerating properties are emerging as valuable options to prevent wound infection and improve the wound healing process. In this study, high porous polyurethane (PU) foams were successfully prepared using salt leaching/solvent casting method and were coated with propolis as a well-known anti-bacterial agent. The wound dressings were subjected to detail analyzes using electron microscopy, reflectance Fourier transform infrared spectroscopy, mechanical properties, contact angle measurement, ratio swelling, porosity measurement, and in vitro and in vivo evaluations. The prepared wound dressings had high porosity (more than 80%) with homogeneous pore structure and sufficient interconnectivity. The increase of propolis concentration (10%-30%) caused tensile strength decrease (5.26 ± 0.40-2.99 ± 0.11 MPa), elongation at break increase (372 ± 12-434 ± 22%), contact angle decrease (114.52 ± 2.31° to 35.53 ± 1.65°), water absorption decreased (243 ± 15-207 ± 14%) and enhancement of the antibacterial activity against Escherichia coli and Staphylococcus aureus. The propolis coated wound dressing exhibited significant enhancement of in vitro cellular compatibility and in vivo wound healing which had direct relative with coated propolis concentration. Therefore, propolis-coated polyurethane wound dressing can be an appropriate candidate for more pre-clinical investigations.

The Effect of Preadsorbed Polyelectrolytes on the Surface Properties and Dispersity of Clay Minerals and Soils

On the basis of adsorption studies, the characteristics of formation of polyelectrolyte (PE) nanoadsorption layers of an aliphatic structure that creates a mineral–organic matrix on clay minerals and soils (kaolinite, montmorillonite, quartz sand, and gray forest and chernozem soils) surfaces have been revealed. It has been established that the polyacrylamide (PAM) and polyacrylic acid (PAA) adsorption limit values on all minerals are significantly higher than the calculated values for the single-layer formation. This indicates the surface adsorption of not only individual macromolecules, but also of secondary PE structures of types of bundles or fibrils determining the cluster-matrix structure of the modified surface. The study of the electric surface properties (electrophoretic mobility, electrokinetic potential, рН, and electroconductivity) of adsorption-modified PE suspensions of minerals and soils has corroborated that there are differences in the adsorption mechanism, ranging from physical to chemisorption with the formation of surface compounds, as a result of both differences between PE polar groups and the mineral type. It has been demonstrated that the mineral and soil surface modification by organic substances differently affects the dispersity, porosity, mean pore radii, total surface area, and pore volume in the direction of both an increase and decrease in size. Here, this results in significant changes in the differential pore volume and more homogeneous pore size distribution.

Microstructures and Properties of Porous Liquid-Phase-Sintered SiC Ceramic by Hot Press Sintering.

Porous liquid-phase-sintered SiC (L-SiC) ceramics were successfully fabricated by hot press sintering (HP) at 1800 °C in argon, using Al2O3 and Y2O3 as oxide additions. By varying the starting coarse SiC particle size, the relationships between pore microstructures and flexural strength as well as gas permeability of porous L-SiC were examined. All the as-sintered samples possessed homogeneous interconnected pores. The porosity of porous L-SiC decreased from 34.0% to 25.9%, and the peak pore size increased from 1.1 to 3.8 μm as the coarse SiC particle sizes increased. The flexural strengths of porous L-SiC ceramics at room temperature and 1000 °C were as high as 104.3 ± 7.3 MPa and 78.8 ± 5.1 MPa, respectively, though there was a decrease in accordance with their increasing pore sizes and particle sizes. Moreover, their gas permeability increased from 1.4 × 10−14 m2 to 4.6 × 10−14 m2 with the increase of pore size in spite of their decreased porosity.

Bioactive chitosan-based scaffolds with improved properties induced by dextran-grafted nano-maghemite and l-arginine amino acid.

Over the past years, fundamentals of magnetism opened a wide research area of interest, in the field of tissue engineering and regenerative medicine. The integration of magnetic nanoarchitectures into synthetic/natural scaffold formulations allowed obtaining "on demand" responsive structures able to guide the regeneration process. The aim of this work was the design and characterization of three-dimensional (3D) chitosan-based scaffolds containing dextran-grafted maghemite nanoarchitectures (DM) and functionalized with l-arginine (l-Arg) amino acid as bioactive agent. A homogeneous pore distribution and a high degree of interconnection were obtained for all the structures with DMs, which resulted well distributed inside the polymer matrix. All the results suggest that the simultaneous presence of DMs and l-Arg conferred interesting mechano-structural and bioactive properties toward osteoblast-like and human mesenchymal stem cells, differentially stimulating their proliferation both in the absence and in the presence of a time-dependent magnetic field. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1244-1252, 2019.

Preparation and characterization of PVA/SA/HA composite hydrogels for wound dressing

A composite hydrogel based on, by introducing, polyvinyl alcohol, sodium alginate, and hyaluronic acid was fabricated using CaCl2 as a cross-linker. The physical properties including morphology, water vapor transmission rate, and hydrophilicity were investigated. All PVA/SA/HA composite hydrogels with different compositions had highly homogeneous and interconnected pores, and the morphologies of the PVA/SA/HA hydrogels ranged from fibrous structure to irregular structure with increasing content of SA. The introduction of sodium alginate enhanced the hydrophilicity and water vapor transmission capacity of the hydrogel; however, the hydrophilicity of the composite hydrogels decreased with the increasing cross-linker content.

SELECTIVE ATENOLOL DETERMINATION IN BLOOD USING MOLECULAR IMPRINTED POLYMER WITH ITACONIC ACID AS FUNCTIONAL MONOMER

Objective: This study was aimed to determine analytical performance and physical character of MI-SPE (Molecular Imprinted Solid Phase Extraction) atenolol using itaconic acid as the functional monomer and to implement the material for the extraction of atenolol in blood serum.Methods: This experiment was performed by determining association constants between monomer-template with UV-Vis spectrophotometer, the synthesis of MI-SPE atenolol using bulk polymerization method, template extraction, evaluation of the adsorption ability and capacity of sorbent, evaluation of sorbent selectivity, and determining their physical character using Fourier Transform Infrared (FTIR) and Scanning Electron Microscope (SEM). In the end, the sorbent then was implemented to extract atenolol in blood serum.Results: Analytical performance showed that MI-SPE sorbent has Imprinting Factor (IF) 10.632 which is the largest number compared to IF when using another beta blocker compound. Physical characterization obtained by MI-SPE using Scanning Electron Microscope (SEM) method showed that MI-SPE morphology has homogeneous pore and number of cavities than its blank. MI-SPE has recovery percentage 92.22 % atenolol when it applied to blood serum spiked with atenolol standard.Conclusion: MI-SPE sorbent made from the itaconic acid monomer in methanol porogen potential to be used for the extraction of atenolol from the blood sample by selectively bind to atenolol.

Forming of Porous Composites with Ti Powder by Self-Assembly of Particles in Polymer Suspensions for Creating Functional Materials

Porous composites on the basis of natrium-carboxymethylcellulose polymer with Titanium powder and AlOOH nanoparticles as a modifier were developed. Morphology of formed structures was examined using REM methods. Influence of AlOOH additives upon suspension surface properties was researched. Evaluation of components interaction power in systems was done; values of wetted angle of contact, adhesion work, cohesion work and work of wetting energy in suspensions were calculated. Peculiarities of self-organization in composition systems with Ti and AlOOH particles were studied. Order strength in the system was evaluated with the help of selective Shannon entropy. The correlation of the smallest Shannon entropy variability with forming relatively homogeneous pores was revealed. Combinations of components proportions within the system with Ti powder and AlOOH nano-sized particles filling, which provide generation of homogeneous pores with the size of ≈250 µm under the temperature of 55°C, were defined. The developed materials may be used as reinforcing elements, sorbents, abrasives, antifriction coatings provided that the matrix pores are filled with lubricants.

A semi-experimental procedure for the estimation of permeability of microfluidic pore network

Microfluidic porous media systems are used for various applications ranging from chemical molecule detection to enhanced oil recovery studies. Absolute permeability data of the microfluidic porous media are important for those applications. However, it is a significant challenge to measure the permeability due to the difficulty in accurately measuring the ultra-low pressure drop across the pore network. This article presents a semi-experimental procedure to estimate the permeability of a microfluidic pore network. The total pressure drop across the porous media chip (ΔPchip) at a given flow rate of a single-phase liquid was obtained from the difference in the inlet pressures at the microfluidic pump with and without the pore network chip connected. The pressure drops in the inlet (ΔPinlet channel) and outlet (ΔPoutlet channel) channels of the pore network are estimated using the hydraulic resistance equation for Poiseuille flow in a wide rectangular cross section. Then the pressure drop across the pore network of the chip (ΔPpore network) is obtained by subtracting (ΔPinlet channel + ΔPoutlet channel) from ΔPchip. Subsequently the permeability of the pore network is calculated using the Darcy’s law.•The proposed method is applicable for both homogenous and heterogeneous pore networks.•This method does not require a differential pressure sensor across the microfluidic chip.•This method eliminates the possibility of gas entrapment that can affect the permeability measurement.

Preparation and Characterization of a PVDF Membrane Modified by an Ionic Liquid

In order to enhance the hydrophobicity of polyvinylidene fluoride (PVDF) porous membranes, the blending of PVDF with a hydrophobic ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) was carried out. The modified PVDF membranes with [Bmim][PF6] were fabricated through a non-solvent induced phase inversion using lithium chloride as a porogen in the PVDF casting solution. The effects of [Bmim][PF6] on the membrane characteristics were investigated. FT-IR analysis indicates that the IL is successfully retained by the PVDF membrane. Thermogravimetric analysis reveals that the optimum temperature of the modified membrane is below 300°C. Scanning electron microscopy pictures show that modified membranes have more homogeneous and larger diameter pores with a mean pore size of 0.521µm and porosity of 78%. By measuring the IL leaching during the membrane fabrication, it was found that the modified membrane does not lose IL. Atomic force microscopy shows that the roughness of the modified membrane surface increases slightly, but the contact angle of the modified membrane increases significantly from 88.1° to 110.1°. The reason for this is that the fluorine-containing IL has a low surface energy, which can enhance the hydrophobicity of the membrane. Finally, by comparing modified membranes with different IL concentrations, we draw a conclusion that the modified membrane with an IL concentration of 3 wt-% has the best properties of pore size, porosity, and hydrophobicity.

Natural gas vaporization in a nanoscale throat connected model of shale: multi-scale, multi-component and multi-phase.

Production of hydrocarbons from shale is a complex process that necessitates the extraction of multi-component hydrocarbons trapped in multi-scale nanopores. While advances in nanofluidics have allowed researchers to probe thermodynamics and transport in single, discrete nanochannels, these studies present a highly simplified version of shale reservoirs with homogeneous pore structures and/or single-component fluid compositions. In this study, we develop and apply a 30 000-pore nanomodel that captures the inherent heterogeneity in reservoir pore sizes (100 nm pores gated by 5 nm-pores) to study vaporization of a representative natural gas hydrocarbon mixture. The nanomodel matches major North American formations in the volumetric and number contributions of the pore sizes, porosity (10.5%), and ultra-low permeability (44 nD). Combined experimental and analytical results show 3000× slower vaporization owing to the nanoscale throat bottlenecks. At low temperatures, mixture effects reduce rates further with stochastic vaporization of light components in large pores dominating. Collectively this approach captures the coupled complexity of multicomponent, multiphase fluids in multiscale geometries that is inherent to this resource.

Ultralow-dielectric, nanoporous poly(methyl silsesquioxanes) films templated by a self-assembled block copolymer upon solvent annealing

A homogenous, nanoporous poly(methyl silsesquixoxane) (PMSSQ) with a uniform pore size distribution was prepared by templating with a poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) block copolymer. The self-assembly of the PS-b-P4VP and PMSSQ precursor (PMSSQ-P) blends thin films was achieved by solvent annealing firstly; then the self-assembled thin films were thermally cured to prepare nanoporous PMSSQ films after removal of the PS-b-P4VP porogen. The influence of annealing solvent and PS-b-P4VP loading on the self-assembly behavior of the PS-b-P4VP/PMSSQ-P blends films were studied. By exposing to CHCl3 vapor, fingerprint-type microphase-separated structures were achieved for the PS-b-P4VP/PMSSQ-P blends films with PS-b-P4VP loading ranging from 30% to 60%. The formation of the microphase-separated structures is attributed to the substantial mobility of the PS blocks and the P4VP/PMSSQ-P complexes, and segregated repulsion between them under the CHCl3 vapor. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) results demonstrated the prepared nanoporous PMSSQ films had a homogenous spherical pore morphology, with closed nanopores and a uniform size distribution over large areas. The porosity and dielectric properties of the homogenous, nanoporous PMSSQ could be adjusted by the content of PS-b-P4VP in the PS-b-P4VP/PMSSQ-P blends. As the PS-b-P4VP loading increased to 60 wt%, an ultralow dielectric constant of 1.41 was obtained, making the nanoporous PMSSQ films have potential applications in microelectronic devices.

Rock physics modelling of elastic properties of organic shale considering kerogen stress and pore pressure distribution

Rock physics model for the elastic properties of organic shale is important for shale oil/gas exploration and production. Up until now, little work has been done to investigate the influence of the distributions of the stress in kerogen (kerogen stress) and the pore pressure on the elastic properties of organic shale. In this work, we used the Kuster- Toksöz (KT) model and Gassmann equation to study such effects. The Gassmann equation was applied for the homogeneous kerogen stress or pore pressure case whereas KT model was suitable for the inhomogeneous case. Four cases with different combinations of kerogen stress and pore pressure distributions, for the elastic properties of organic shale, were analysed and the corresponding models were given. Based on these models, a numerical example was studied. The results showed that the distributions of kerogen stress and pore pressure significantly affect the elastic properties of organic shale. The elastic moduli under the inhomogeneous kerogen stress or pore pressure distributions are larger than the homogeneous case, whose magnitude depends on porosity and kerogen content. Furthermore, the joint effects of kerogen stress and pore pressure distributions are similar to those of kerogen stress due to the much smaller effects of pore pressure. Hence, it is essential to consider the effects of the distributions of kerogen stress and pore pressure when building the rock physics model for the elastic properties of organic shale. This work revealed the importance of kerogen stress and pore pressure distributions on the elastic properties of organic shale and hence is helpful for the shale oil/gas exploration and production.

Limit Models of Pore Space Structure of Porous Materials for Determination of Limit Pore Size Distributions Based on Mercury Intrusion Data

This paper proposes the application of capillary and chain random models of pore space structure for determination of limit pore diameter distributions of porous materials, based on the mercury intrusion curves. Both distributions determine the range in which the pore diameter distribution of the investigated material occurs and defines the degree of inaccuracy of the method based on the mercury intrusion data caused by the indeterminacy of the sample shape and its pore space architecture. We derived equations describing the quasi-static process of mercury intrusion into the porous layer and porous ball with a random chain pore space structure and analysed the influence of the model parameters on the mercury intrusion curves. It was shown that the distribution of link length in the chain model of the pore space, random location of chain capillaries in the sample and the length distribution of the capillaries do not influence significantly the intrusion process. Therefore, a simple model of the mercury intrusion into the layer is proposed in which chain links of the pore space have random diameters and constant length. This model is used as a basic model of the intrusion process into a sample of any shape and size and with homogeneous and isotropic chain pore space architecture. The thickness of the layer then represents the mean length of chain capillaries in the sample. It was also proved that the capillary and chain models of pore space architecture are limit models of the network model identified in this paper with the pore architecture of the investigated sample. This justifies the application of both models for determination of limit cumulative distributions of pore diameters in porous materials based on the mercury intrusion data.

GAS CONCRETE FOR CONSTRUCTION OBJECTS OF TRANSPORT INFRASTRUCTURE

Introduction.Construction objects of transport infrastructure have different influence and service conditions. An actual technical task is the design of optimal microclimate for human operation in workshops and office buildings. Therefore, such conditions can be achieved by using of construction material with high parameters of heat- and sound-insulation such as a gas concrete. The main task of the research is the improvement of heat- and sound-insulation in the gas concrete.Materials and methods.The evaluation of the gas concrete efficiency is based on the research of such parameters as heat- and sound-insulation. The analysis of the material at macro- and micro-level is performed with SEM-analysis and BET-analysis. In addition, the complex of experimental and calculated data of physical and chemical characteristics for gas concrete is carried out.Results.As a result, the usage of amorphous alum inosilicate raw materials in gas concrete allows variation of parameters to effect on pore structure such as homogeneous pore distribution in bulk, thickness and density of interpore partition, pore shape and pore size. The reduction of aerated concrete density by 22.5 % leads to reducing of heat conductivity by 19.26 %. The formation of cellular structure with mainly closed pores allows reducing of sorption humidity and vapor permeability of material under different environmental humidity.Differently-sized pores in the gas concrete and predominantly small pores with size of 0.3-0.9 mm as well as with size up to 94,6 nm leads to increasing isolation index of airborne sound due to increasing of absorption of acoustic wave in frequency range of 125-4000 Hz. Complexly, it provides high sound-insolating parameters of wall envelopes.Discussion and conclusions.Monitoring of heat- and sound-insolation of the gas concrete due to optimization of pore structure allows formation of energy effective composites able to protect humans from unfavorable environment in the transport enterprises.