Maximum Pore Diameter Research Articles

Preparation and application of highly porous aerogel-based bioactive materials in dentistry

In this study, the possibility of preparation and application of highly porous silica aerogel-based bioactive materials are presented. The aerogel was combined with hydroxyapatite and β-tricalcium phosphate as bioactive and osteoinductive agents. The porosity of aerogels was in the mesoporous region with a maximum pore diameter of 7.4 and 12.7 nm for the composite materials. The newly developed bioactive materials were characterized by scanning electron microscopy. The in vitro biological effect of these modified surfaces was also tested on SAOS-2 osteogenic sarcoma cells by confocal laser scanning microscopy.

Investigation of Coronal Leakage of Root Fillings after Smear Layer Removal with EDTA or Er,Cr:YSGG Laser through Capillary Flow Porometry

No studies have been performed evaluating the marginal seal of root fillings after direct exposure of root canal (RC) walls to Er,Cr:YSGG laser irradiation. Therefore, 75 root filled teeth (5 × 15–cold lateral condensation) were analyzed for through-and-through leakage (TTL) using capillary flow porometry (CFP). The cleaning protocol determined the experimental groups: (1) irrigation with NaOCl 2.5% and EDTA 17% or standard protocol (SP), (2) SP + Er,Cr:YSGG lasing (dried RC), (3) NaOCl 2.5% + Er,Cr:YSGG lasing (dried RC), (4) SP + Er,Cr:YSGG lasing (wet RC), and (5) NaOCl 2.5% + Er,Cr:YSGG lasing (wet RC). Groups 6 to 10 consisted of the same filled teeth with resected apices. Resection was performed after the first CFP measurement. CFP was used to assess minimum, mean flow, and maximum pore diameters after 48 h. Statistics were performed using nonparametric tests (P > 0.05). Additional three roots per group were submitted to SEM of the RC walls. TTL was observed in all groups without statistically significant differences between the different groups for minimum, mean, and maximum pore diameter (P > 0.05). In this study, the use of EDTA and/or Er,Cr:YSGG laser did not reduce through-and-through leakage in nonresected and resected roots.

Fractal analysis of dimensionless capillary pressure function

The dimensionless capillary pressure function J(SW) was used to eliminate the capillary pressure difference between different strata and to describe similar lithologic reservoirs. Based on the existing function J(SW) and the fractal geometry theory, a fractal model to describe the pore structure of the lithology is presented. The proposed fractal expression for the J(SW) function reveals that when the microstructural parameters (fractal dimension for pore area, the fractal dimension for tortuosity, and the ratio of the maximum pore diameter to the minimum pore diameter) are respectively equal or close for porous samples (with different permeabilities, porosities, interfacial tensions and wetting angles), the values of the J(SW)function vs. saturation coincide each other for wetting phase. In addition, a new dimensionless function G(SW), which is based on the ratio of the average capillary diameter to the critical capillary diameter, is proposed to describe the relationships among the structural parameters of similar lithological porous media and saturation as well as the dimensionless capillary pressure function J(SW).

Physico-Chemical Characterization and Interfacial Electrochemical Properties of Nanoparticles of Anatase-TiO2 Prepared by the Sol-Gel Method

In this work, we prepared by the sol-gel method titanium dioxide nanoparticles having a large specific area (SBET = 218 m2/g). The isotherm of N2 adsorption-desorption at 77K revealed that it concerns a mesoporous solid with a maximum pore diameter of 43 Å. The X-ray diffraction showed that the solid is constituted of the anatase phase. The transmission electron microscopy revealed us that the synthesized grains of TiO2 are of nanometric sizes (diameter between 8 and 20 nm) and manifest under agglomerated shape. The study of its solubility in dispersing phase, by conductometric titrations, showed that the prepared solid is totally insoluble in all the domain of the studied pH. The measured inter-facial electrochemical properties, based on the isotherms of ionic adsorption and the conductometric titrations, are: the point of zero charge found equal to 6,2±0,1, the total number of sites of surface found equal to 5,8 OH/nm2 and the nature of action of the dispersed phase on the dispersing phase which is found organizer of the structure of water. Besides, the difference of the ionization constants pK is found superior to 4 for all the adsorbed ions and the constants of surface complexation are independent from the nature of the adsorbed ion.

Rapid adsorption properties of flower-like BiOI nanoplates synthesized via a simple EG-assisted solvothermal process

Uniform well-crystallized flower-like BiOI nanoplates contained 3.7 nm mesopores, which may be attributed to the internanosheet spaces of BiOI with maximum pore diameters of about 30 nm, were successfully synthesized via a simple ethylene glycol-assisted solvothermal method. The as-prepared porous BiOI nanoplates exhibited excellent adsorption ability, and the saturated extent of adsorption of BiOI over an RhB solution was as high as 197 mg/g, which is much higher than those for BiOCl and BiOBr prepared via the same method and with a similar surface area. The probable adsorption mechanism could have originated from the interaction between the I atom in BiOI and a proton in RhB at different pH values and temperatures. With visible light irradiation (λ > 420 nm), 80 % of the RhB was degraded in 4 h, while BiOI still demonstrated reasonably outstanding photocatalytic ability under green light (λ = 550 ± 15 nm) because of its low-energy gap (1.72 eV). The degradation test for BiOI under irradiation at λ = 550 ± 15 nm is an excellent achievement for field applications because the catalyst can be applied in solar irradiation to remove organic pollutants, which may be of great value BiOI complex.

Influence of Anodizing Parameters on Pore Diameter of Anodic Aluminium Oxide (AAO) Films Using Taguchi Design

Nanoporous anodic aluminium oxide (AAO) films were fabricated by using a two-step anodizing process of aluminium foils in oxalic acid electrolyte. The effect of synthesis conditions including applied voltage, electrolyte concentration and temperature on the pore diameter of AAO films was investigated. To reduce the number of experiments, the Taguchi L9 orthogonal array was adopted and the results were analyzed using minitab15 software. It was found that the pore size increased in direct proportion with the applied voltage. The proportion of the pore size with increasing electrolyte concentration was at first direct and then inverse and the maximum pore diameter was obtained in the case of 0.3 M. The pore size relation with increasing electrolyte temperature was at first inverse and then direct and the minimum pore diameter was seen at 10 ◦C. The diameter of the nanopores were predicted with the software in the range of 35–71 nm in different conditions of selected experimental parameters. Also, as a practical application of obtained AAO films, template-synthesis fabrication of polypyrrole nanowire arrays by electrochemical polymerization of pyrrole within the pores of the obtained AAO was successfully demonstrated.

Fractal analysis of spontaneous imbibition mechanism in fractured-porous dual media reservoir

Low permeability oil reservoirs are usually accompanied with fracture development, forming fracture-matrix dual porosity medium. Spontaneous imbibition is a crucially important recovery mechanism in naturally fractured reservoir with water deriving, in which non-wetting phase is displaced in either co-current or counter-current manner. In this work, the criterion (inverse bond number) and fractal model for spontaneous imbibition mechanism of dual-porosity medium are developed, and the analytical expression for structure constant is also derived based on the fractal characteristics of pores in porous matrix. The improved fractal model for inverse bond number can be expressed as a function of porosity, pore fractal dimension, flow tortuosity, maximum pore diameter, height of matrix, density difference between oil and water, interfacial tension and contact angle. The present model predictions are shown to be in agreement with the available results. The dominion for criterion of imbibition mechanism is plotted, which provides a theoretical basis of adding surfactant in water for enhancing oil recovery in low permeability reservoirs.

Determination of Pore Sizes and Relative Porosity in Porous Nanoshell Architectures Using Dextran Retention with Single Monomer Resolution and Proton Permeation

Unilamellar phospholipid vesicles prepared using the polymerizable lipid bis-sorbylphosphatidylcholine (bis-SorbPC) yield three-dimensional nanoarchitectures that are highly permeable to small molecules. The resulting porous phospholipid nanoshells (PPNs) are potentially useful for a range of biomedical applications including nanosensors and nanodelivery vehicles for cellular assays and manipulations. The uniformity and size distribution of the pores, key properties for sensor design and utilization, have not previously been reported. Fluorophore-assisted carbohydrate electrophoresis (FACE) was utilized to assess the nominal molecular weight cutoff limit (NMCL) of the PPN via analysis of retained dextran with single monomer resolution. The NMCL of PPNs prepared from pure bis-SorbPC was equivalent to a 1800 Da linear dextran, corresponding to a maximum pore diameter of 2.6 nm. Further investigation of PPNs prepared using binary mixtures of bis-SorbPC and dioleoylphosphatidylcholine (DOPC) revealed a similar NMCL when the bis-SorbPC content exceeded 30 mol %, whereas different size-dependent permeation was observed below this composition. Below 30 mol % bis-SorbPC, dextran retention provided insufficient mass resolution (162 Da) to observe porosity on the experimental time scale; however, proton permeability showed a marked enhancement for bis-SorbPC ≥ 10 mol %. Combined, these data suggest that the NMCL for native pores in bis-SorbPC PPNs results from an inherent property within the lipid assembly that can be partially disrupted by dilution of bis-SorbPC below a critical value for domain formation. Additionally, the analytical method described herein should prove useful for the challenging task of elucidating porosity in a range of three-dimensional nanomaterials.

An analytical model for spontaneous imbibition in fractal porous media including gravity

Spontaneous imbibition of wetting liquid into porous media is regarded as a crucially important driving mechanism for enhancing oil recovery from naturally fractured reservoir, especially with low permeability. Based on the fractal character of pores in porous media, a full analytical model for characterizing spontaneous imbibition of wetting liquid vertically into gas-saturated porous media has been derived including gravity over the entire imbibition process time frame. The weight of wetting liquid imbibed into porous media is a function of contact area, porosity, pore fractal dimension, tortuosity, maximum hydraulic pore diameter, liquid density, viscosity, surface tension and liquid–solid interactions. Factors influencing the imbibition process upon approaching equilibrium weight were also analyzed. The proposed analytical model is consistent with the previous models and the predictions are in good agreement with available experimental data published in the literature.

A study of hydrophobic electrospun membrane applied in seawater desalination by membrane distillation

In this study, two composite nanofibrous membranes of Polyvinylidenefluoride (PVDF) and [poly(vinylidenefluorideco-hexafluoropropylene)] (PVDF-co-HFP) prepared by the electrospinning process were employed in a direct contact membrane distillation (DCMD) system. We changed the pump flow rate and temperature difference to examine their effects on permeate flux and salt rejection. The SEM observations, porosity analyzer technique, and contact angle measurement indicated the nanobrous membrane with an average fiber diameter of 170 nm and maximum pore diameter distribution of 0.3 µm is the best membrane for the DCMD system. However, the ability of the hydrophobic membrane affects the filtration efficiency of the DCMD system. The contact angle of the PVDF-HFP electrospun membrane (128°) shows better hydrophobic than the PVDF electrospun membrane (125 °). From the experiment of 12 hours, the salt rejection of PVDFHFP (99.9901 %) was better than that of PVDF composite membrane (99.9888 %) and was almost the same as that of the PTFE commercial membrane (99.9951 %). In addition, the permeate flux of the PVDF-HFP composite membrane is 4.28 kg/ m2hr higher than the PTFE commercial membrane.

Neck-size distributions of through-pores in polymer membranes

Abstract Capillary flow porometry (CFP) is used for measuring the most constricted part (bottleneck) of through-pores in synthetic membranes. In present work, a systematic study has been carried out to evaluate influence of membrane properties like tortuosity, intersecting pores and thickness on CFP. For evaluating CFP, the track-etched membranes were used as these membranes have cylindrical pores. The average, maximum and minimum pore diameters and pore-diameter distributions in the track-etched membranes were obtained by CFP, and compared with the values obtained by different techniques like atomic force microscopy (AFM), scanning electron microscopy (SEM) and molecular weight cut-off (MWCO). The internal architecture of pore in the track-etched membranes was studied by growing gold nano-rods in the pores. The gold nano-rods were grown in the membrane by electrodeposition using removable electrode (Hg). The transmission electron microscopy (TEM) of nano-gold rods were carried out after dissolution of the membranes in dichloromethane. The studies carried out in the present work showed that: (i) the CFP data remained practically independent of the membrane thickness and tortuosity, (ii) it measured the most constricted diameter of a pore independent of pore-architecture, and (iii) mean flow pore-diameters data were highly reproducible (±5%). The capability of CFP for assessing quality of the membrane was demonstrated using the pore-filled membrane samples having different amounts of the crosslinked poly- N -isopropylacrylamide (poly-NIPA). These samples were prepared by UV-initiator induced in situ photo-polymerization of NIPA in pores of the host microporous poly(propylene) membrane.

Preparation of Porous Ti Plate with Nanograde Pore Size by Dip-Coating Method

The porous Ti plates with nanograde pore size were successfully prepared by dip-coating technique, using stainless steel plates as support and 400mesh Ti powders as raw material. The stainless steel plates were firstly dipped into Ti slurry and then pulled out with desired withdrawal velocity. After sintered in a vacuum furnace, stainless steel supports were removed by aqua regia. The obtained products were characterized by X-ray diffraction, sanning electron microscope and N2 adsorption–desorption isotherms. The results had shown that the thickness and pore characters of porous Ti plates could be controlled by adjusting the withdrawal velocity. When the withdrawal velocity was controlled between 0.2mm/s and 1mm/s, the porous Ti plates had smooth surface without cracks and the most pores were interconnected. The maximum pore diameters could be less than 300nm and the porosities of porous Ti plates are more than 4.9%. The kind of preparation method has advantages of simple technology, easy operation and high purity. These indicated that the porous sintering Ti plates were promising to be used as ultrafilter membranes.

Fabrication of Nanoporous Alumina and Their Structural Characteristics Study Using SEM Image Processing and Analysis

Nanoporous anodic aluminum oxide (AAO) membranes were fabricated by a two-step anodization process. Quantitative structural characterization was carried out using scanning electron microscopy images of the fabricated anodized alumina. An algorithm based on mathematical morphology was developed to extract pore size distribution with average, minimum, and maximum pore diameter of the nanoporous alumina. This technique of obtaining quantitative data based on image analysis could be an efficient, unbiased, and reliable method and can be used to control the fabrication parameters of anodization process.

Influence of the gelation and calcination temperatures on physical parameters and photocatalytic activity of mesoporous titania powders synthesized by the nonhydrolytic sol–gel process

Titania powders were synthesized by nonhydrolitic sol–gel process starting from titanium(IV)-chloride, titanium(IV)-isopropoxide and carbon-tetrachloride. Gelation was performed in solvothermal conditions, at 140°C or 160°C. The obtained gels were then dried and calcined at 500°C or 750°C.Dry gels and powders obtained by their calcination at 500°C contained only anatase, and the degree of crystallinity increased notably on passing from the dry gels to the powders. The crystallite size of dry gels and powders obtained at 500°C increased slightly with increasing temperature of the gelation. The powder obtained at the higher gelation temperature had a larger specific surface area (52.8m2g−1) and a smaller maximum pore diameter (12.3nm). When the calcination temperature was increased to 750°C, the obtained powders contained both anatase and rutile. The rutile content in the powders is related to the degree of crystallinity of the dry gels: with a lower level of dry gel crystallinity, the rutile content in the powders becomes higher, indicating that the temperature of the anatase→rutile transformation decreases with decreasing the size of anatase crystallites. The photocatalytic activity of the powders obtained by gel calcination at 500°C, tested by measuring the photocatalytic degradation of the azo dye CI Reactive orange 16, was sufficiently high and attained the photocatalytic activity of the broadly accepted commercial powder P-25 produced by Degussa. The photocatalytic activity of the powders obtained by calcination at 750°C was low, but showed a tendency to increase with higher anatase content in the powders.

Hydrophilic and hydrophobic double microporous layer coated gas diffusion layer for enhancing performance of polymer electrolyte fuel cells under no-humidification at the cathode

Gas diffusion layers (GDLs) coated with a hydrophobic microporous layer (MPL) have been commonly used to improve the water management properties of polymer electrolyte fuel cells (PEFCs). In the present study, a new hydrophilic and hydrophobic double MPL coated GDL was developed to achieve further enhancement of PEFC performance under no-humidification at the cathode. The hydrophobic MPL, which consists of carbon black and polytetrafluoroethylene (PTFE), was coated on the carbon paper substrate. The hydrophilic layer, which consists of carbon black and polyvinyl alcohol (PVA), was also coated on the hydrophobic MPL. The hydrophilic layer is effective for conserving humidity at the catalyst layer, while the hydrophobic intermediate layer between the hydrophilic layer and the substrate prevents the removal of water in the hydrophilic layer via dry air in the substrate. Both decrease in the hydrophilic layer thickness to 5 μm and appropriate enhancement of hydrophilicity by increasing the PVA content to 5 mass% are effective for enhancing PEFC performance. Reducing the maximum pore diameter of hydrophobic intermediate layer to 20 μm is also effective for enhancing PEFC performance. However, when the pore diameter of the hydrophobic layer becomes too small, concentration overpotential tends to increase, thereby lowering PEFC performance.

Effect of uni-axial loading on the nanostructure of silica aerogels

Aerogels are unique materials offering a combination of remarkable properties that make them useful in a wide range of applications. However, aerogel materials can be difficult to work with because they are fragile. The intent of the work presented here was to study the relationship between axial loading and pore structure in aerogel material. Silica aerogel samples with a bulk density of 0.1 g/mL were compressed by uni-axial force loads from 1 to 5 kN which resulted in stress levels up to 23 MPa. The resulting change in the pore distribution was observed using nitrogen desorption analysis and scanning electron microscopy. Uncompressed aerogel samples exhibit peak pore volume at diameters of about 20 nm. As the aerogels are subjected to increased loading, the location of the peak volume moves to smaller diameters with a reduced volume of pores occurring above this diameter. The peak diameter, the average pore diameter and pore volume all decrease and scale with increasing maximum stress while the surface area of the aerogel samples remains unaffected at about 520 m 2/g. When combined with data from the literature, the relation between maximum pore diameter and applied stress suggests a failure mechanism dominated by bending induced fracture.

Carbon microspheres with embedded magnetic iron oxide nanoparticles

Narrow-size disperse porous carbon microspheres with embedded magnetite nanoparticles were prepared by annealing Fe(III)-containing microspheres composed of a copolymer of acrylic acid and divinylbenzene at 800 °C under inert atmosphere. The Fe(III)-containing microspheres were prepared by uptake of Fe 2+ ions through ion exchange process by poly(acrylic acid-divinylbenzene) microspheres that were prepared by distillation–precipitation polymerization, followed by annealing at 250 °C at ambient atmosphere. The carbonization of the microspheres created micropores with a maximum pore diameter of about 0.38 nm and a BET surface area of ~ 200 m 2/g. The saturation magnetization of the magnetic carbon microspheres was 31.5 emu/g with a low remnant magnetization and coercivity.

EFFECT OF SOME FACTORS ON FABRICATION OF POLY(L-LACTIC ACID) MICROPOROUS FOAMS BY THERMALLY INDUCED PHASE SEPARATION USING N,N-DIMETHYLACETAMIDE AS SOLVENT

Biocompatible, highly interconnected microporous poly(L-lactic acid) (PLLA) foams or scaffolds with nano-fibrous structure, containing pores with diameters of 0.1–3.5 μm and fibers with diameters of 300–700 nm scale, were prepared through the thermally induced liquid–liquid phase separation (TIPS) method using N,N′-dimethyl acetamide (DMAc) as solvent. Various foam morphologies were obtained by changing parameters involved in the TIPS process, such as polymer concentration, solvent composition, and quenching temperatures. The morphology of different foams was examined by scanning electron microscopy, whereas the pore size and the pore size distribution were calculated. The results showed that most porous foams presented nano-fibrous structure with interconnected open pores. In the case of using DMAc as solvent, with increasing polymer concentration, either the average pore diameter or the pore size distribution exhibited a maximum value at 0.05 g/mL polymer concentration and quenching temperature of −30°C. It was found that all the pore size distribution fit the F-distribution equation. With increasing the quenching temperature from −30°C to −10°C, the maximum average pore diameter of the foams decreased and the pore size distribution became narrower, whereas the polymer concentration exhibiting the maximum pore size and widest pore size distribution increased from 0.05 g/mL to 0.07 g/mL. In the case of using the mixed solvent of DMAc/DOX (1,4-dioxane) from 9/1 to 7/3 (v/v) there appeared a maximum value of average pore diameter and a widest pore size distribution all at 0.05 g/mL PLLA concentration and quenching temperature of −30°C. The maximum pore size tends to increase with increasing DOX content.

Investigation of Coronal Leakage of Root Fillings After Smear-Layer Removal with EDTA or Nd:YAG Lasing Through Capillary-Flow Porometry

This study investigates the effects of Nd:YAG laser irradiation combined with different irrigation protocols on the marginal seal of root fillings. Limited information exists regarding the effects of morphologic changes to root canal (RC) walls after Nd:YAG laser irradiation after smear-layer removal with EDTA on the sealing ability of root fillings. The 75 root-filled teeth (5 × 15 teeth) were analyzed for through-and-through leakage by using capillary flow porometry (CFP). The RC cleaning procedure determined the assignment to a group: (1) irrigation with NaOCl 2.5% and EDTA 17% or standard protocol (SP), (2) SP + Nd:YAG lasing (dried RC), (3) NaOCl 2.5% + Nd:YAG lasing (dried RC), (4) SP + Nd:YAG lasing (wet RC), or (5) NaOCl 2.5% + Nd:YAG lasing (wet RC). Groups 1r to 5r consisted of the same filled teeth with resected apices up to the most apical point of the preparation length. Resection was performed after the first CFP measurement. Roots were filled with cold lateral condensation. CFP was used to assess minimum, mean flow and maximum pore diameters after 48 h, and immediately after these measurements, including root resection. Statistics were performed by using nonparametric tests (p > 0.05). An additional three roots per group were submitted to SEM of the RC wall. Through-and-through leakage was observed in all groups. Statistically significant differences were observed in maximum pore diameter: 1r > 3r, and 1r > 5r; in mean flow pore diameter: 1r > 2r, 2r < 4r (p < 0.05). Typical Nd:YAG glazing effects were observed when the smear layer was present and exposed to the laser fiber (i.e., in the groups without use of EDTA) or when the fiber tip made direct contact with a smear-layer free RC wall. The reduction in through-and-through leakage is significantly higher with the Nd:YAG laser as smear-layer modifier than when smear layer is removed with an EDTA rinsing solution.

Controlled nanopore formation and stabilization of gold nanocrystals in acid-activated montmorillonite

Au o-nanoparticles of 0–10 nm were generated in situ by the reduction of [AuCl 4] − impregnated on acid-activated montmorillonites with maximum pore diameters of about 3, 4, 6, and 8 nm. The size of the Au o-nanoparticles depended on the pore diameter of the micro- and mesopores of the support. The montmorillonite was activated with HCl under control conditions for generating different pore sizes. Powder X-ray diffraction (XRD), FTIR, FESEM-EDX, HRTEM, N 2 adsorption, 29Si and 27Al MAS-NMR and UV–visible spectroscopic analyses were carried out to characterize the solid porous materials before and after Au o-nanoparticle loading. N 2 adsorption data revealed specific surface areas (BET) of 327–579 m 2/g, large specific pore volumes of ∼ 0.7 cm 3/g, and pore diameters of 0–10 nm. TEM, FESEM and X-ray mapping images revealed Au o-nanoparticles of 0–10 nm evenly distributed on the support. The Au o-nanocrystal composites exhibited the cubic face-centered (fcc) lattice with a preferential growth direction along the (111) plane.