Submicron Pores Research Articles

Insights into Diagenesis and Pore Structure of Opalinus Shale Through Comparative Studies of Natural and Reconstituted Materials

AbstractShales have undergone a complex burial diagenesis that involved a severe modification of the pore structure. Reconstituted shales can provide new insights into the nature of the pore structure in natural materials. The effects of diagenesis on the microfabric, pore size distribution, and porosity of Opalinus shale were measured by comparing the behavior of natural and reconstituted specimens. The parent material (Opalinus shale) was reconstituted through multiple grinding operations, sedimentation from a dispersed slurry, and one-dimensional isothermal consolidation. This process produced uniform specimens that were not cemented and had replicable microfabric and engineering properties. The microfabric and mineralogy of the materials were examined using high-resolution scanning/backscattered electron microscopy (SEM/BSEM) and energy-dispersive X-ray spectroscopy (EDS) for specimens with broken and milled surfaces. Mercury intrusion porosimetry (MIP) and N2 adsorption were used to assess the pore size distributions and specific surface areas of the materials. The microstructure of natural shale was characterized to be highly heterogeneous with significant concentrations of calcareous microfossils, calcite, and quartz particles embedded within the clay matrix. The microfossils were observed to be locally infilled and rimmed by a calcite cement that showed evidence of dissolution. The reconstituted specimens showed a double-structure microfabric that evolved with the level of consolidation stress and converged into a single-structure material (comparable to the natural shale) at a consolidation stress of more than twice the estimated maximum in situ effective stress. The natural shale had a lower specific surface area in comparison to the reconstituted material, which was consolidated at large effective stresses. These differences can be attributed to cementation at a submicron pore scale and highlight chemical diagenesis effects that were not replicated in the reconstituted specimens.

Poly(vinylidene fluoride) fibrous membranes doped with polyamide 6 for highly efficient separation of a stable oil/water emulsion

ABSTRACTIdeal membranes toward separation of stable oil/water emulsions should have surface hydrophilicity and submicron pores in the separating layer. However, electrospun membranes made from poly(vinylidene fluoride) (PVDF) cannot meet these requirements, failing to remove oil droplets from a stable oil/water emulsion. By doping with a certain polyamide 6 solution, surface hydrophilicity, and interconnected pores with submicron size are successfully achieved. As a result, separation of a stable emulsion with an efficiency above 99% is exhibited by the modified PVDF membranes. Moreover, underwater oleophobicity of the modified PVDF membranes imparts them with good antifouling performance. The modified PVDF membranes could have great potentials in practical stable oil/water emulsion separation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44980.

Cellulose Acetate Based Material with Antibacterial Properties Created by Supercritical Solvent Impregnation

Supercritical CO2 was used as a green solvent and impregnation medium for loading cellulose acetate beads with carvacrol in order to obtain a biomaterial with antibacterial properties. Supercritical solvent impregnation was performed in a high-pressure view cell at temperature of 50°C and pressures of 10, 21, and 30 MPa with the processing time ranging from 2 to 18 h. The rate of impregnation increased with the pressure increase. However, maximum impregnation yield (round 60%) was not affected by the pressure applied. Selected samples of the impregnated cellulose acetate containing 6–60% of carvacrol were proven to have considerable antibacterial effect against Gram-positive and Gram-negative bacterial strains including methicillin-resistant Staphylococcus aureus which causes severe infections in humans and animals. In addition, cellulose acetate beads containing 6.0–33.6% of carvacrol were shown to have a porous structure with submicron pores which is of interest for the controlled delivery applications.

抗重力型ループヒートパイプの研究

This paper proposes a meters-class anti-gravity loop heat pipe with Shirasu Porous Glass(SPG) as a wick for the smart thermal management of house. SPG shows excellent capillary force against anti-gravity and high permeability based on submicron pore radius and porosity over 50 %. Furthermore, five layers PTFE filters which have low thermal conductivity were applied on the SPG wick to reduce the heat leak from the evaporator to the compensation chamber. The proposed anti-gravity LHP were designed and fabricated based on the one-dimensional steady-state numerical model. Experiments of heat load were conducted under 2 m and 4 m anti-gravity conditions and those results showed the stable operation. Finally, the LHP performance was evaluated by calculating the thermal resistance between the evaporator to the condenser.

Sub-micron pore size tailoring for efficient chiral discrimination.

Adsorption studies in microporous organically pillared layered silicates (MOPS) show that precise control of micropore size in the sub-Ångström range is crucial for chiral discrimination. The highly modular character of MOPS generally allows for an optimization of guest recognition without the need to explore different framework topologies.

Manganese Dioxide Electrode: Attempts to Increase the Electrochemical Utilization

Manganese dioxide has been the subject of intense research in recent years since it has been demonstrated that they are characterized by pseudocapacitor properties. Furthermore, hybrid electrochemical capacitor using a negative carbon electrode and positive manganese dioxide electrode together with an aqueous electrolyte allows to prepare a device with a higher cell voltage than either carbon/carbon or manganese dioxide/manganese dioxide symetrical electrochemical capacitor. Unfortunately, the high theoretical specific capacity of a manganese electrode cannot be obtained when thick and industrially relevant electrodes are investigated. In fact, no more than 20% of the manganese dioxide-based electrode material is electrochemically addressable. In this talk, attempts to increase the electrochemical utilization of manganese dioxide will be presented. Our recent studies focussing on the effect of carbon additives, shape of manganese dioxide particles, electrode formulation and electrolyte, including water-in-salt electrolyte, on the performance of manganese dioxide electrode tested in the three-electrode configuration (single electrode characterization) and as a full system will be investigated (1-4). 1. A. Gambou Bosca, D. Bélanger, Effect of the formulation of the electrode on the pore texture and electrochemical performance of the manganese dioxide-based electrode for application in a hybrid electrochemical capacitor. Journal of Materials Chemistry A., 2014, 2, 6463-6473. 2. A. Gambou Bosca, D. Bélanger, Chemical mapping and electrochemical performance of manganese dioxide/activated carbon based composite electrode for asymmetric electrochemical capacitor. Journal of the Electrochemical Society. 2015, 162, A5115-A5123. 3. A. Gambou Bosca, D. Bélanger, Electrochemical accessibility of porous submicron MnO2 spheres as active electrode materials for electrochemical capacitors, Electrochimica Acta, accepted.4. A. Gambou Bosca, D. Bélanger, Electrochemical Characterization of MnO2-Based Composite in the Presence of Salt-in-Water and Water-in-Salt Electrolytes as Electrode for Electrochemical Capacitors, J. Power Sources, submitted.

Enhanced lithium storage performance of a self-assembled hierarchical porous Co3O4/VGCF hybrid high-capacity anode material for lithium-ion batteries

A Co3O4/vapor-grown carbon fiber (VGCF) hybrid material is prepared by a facile approach, namely, via liquid-phase carbonate precipitation followed by thermal decomposition of the precipitate at 380 °C for 2 h in argon gas flow. The material is characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller specific surface area analysis, and carbon elemental analysis. The Co3O4 in the hybrid material exhibits the morphology of porous submicron secondary particles which are self assembled from enormous cubic-phase crystalline Co3O4 nanograins. The electrochemical performance of the hybrid as a high-capacity conversion-type anode material for lithium-ion batteries is investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic discharge/charge methods. The hybrid material demonstrates high specific capacity, good rate capability, and good long-term cyclability, which are far superior to those of the pristine Co3O4 material prepared under similar conditions. For example, the reversible charge capacities of the hybrid can reach 1100–1150 mAh g−1 at a lower current density of 0.1 or 0.2 A g−1 and remain 600 mAh g−1 at the high current density of 5 A g−1. After 300 cycles at 0.5 A g−1, a high charge capacity of 850 mAh g−1 is retained. The enhanced electrochemical performance is attributed to the incorporated VGCFs as well as the porous structure and the smaller nanograins of the Co3O4 active material.

A Theory for Relative Permeability of Unconventional Rocks With Dual-Wettability Pore Network

Summary Recent studies show that the pore network of unconventional rocks, such as gas shales, generally consists of inorganic and organic parts. The organic part is strongly oil-wet and preferentially imbibes the oleic phase. In contrast, the inorganic part is usually hydrophilic and preferentially imbibes the aqueous phase. Conventional theories of relative permeability, which are based on uniform wettability, cannot be applied to determine phase permeability in unconventional rocks with dual-wettability behavior. The objective of this paper is to extend the previous theories to model relative permeability of dual-wettability systems in which oleic and aqueous phases can both act as wetting phases in hydrophobic and hydrophilic pore networks, respectively. In the first part of the paper, we review and discuss the results of scanning electron microscopy (SEM), organic petrography, mercury injection capillary pressure (MICP), and comparative water/oil imbibition experiments conducted on several samples from the Triassic Montney tight gas siltstone play of the Western Canadian Sedimentary Basin. We also discuss various crossplots to understand the reasons behind the observed dual-wettability behavior, and to investigate the spatial distribution and morphology of hydrophilic and hydrophobic pores. In the second part, Purcell's model (Purcell 1949) is extended to develop a conceptual model for relative permeability of gas and water in a dual-wettability system such as the Montney tight gas formation. Finally, the proposed model is compared with measured relative permeability data. The results suggest that the submicron pores within solid bitumen/pyrobitumen are strongly water-repellant; therefore, they prefer gas over water under different saturation conditions. This part of the pore network is usually represented by a long tail at the lower end of the pore-throat-size distribution determined from MICP. The proposed relative permeability model describes single-phase flow of gas through the tail part, and two-phase flow of gas and water through the remaining bell-shaped part of the pore-throat-size distribution, which dominantly represents inorganic micropores. On the basis of our model, by increasing the fraction of water-repellant submicron pores, gas relative permeability decreases for a fixed water saturation. This decrease is ascribed to the reduction of the average size of flow conduits for the gas phase.

In situ 3‐D mapping of pore structures and hollow grains of interplanetary dust particles with phase contrast X‐ray nanotomography

AbstractUnlocking the 3‐D structure and properties of intact chondritic porous interplanetary dust particles (IDPs) in nanoscale detail is challenging, which is also complicated by atmospheric entry heating, but is important for advancing our understanding of the formation and origins of IDPs and planetary bodies as well as dust and ice agglomeration in the outer protoplanetary disk. Here, we show that indigenous pores, pristine grains, and thermal alteration products throughout intact particles can be noninvasively visualized and distinguished morphologically and microstructurally in 3‐D detail down to ~10 nm by exploiting phase contrast X‐ray nanotomography. We have uncovered the surprisingly intricate, submicron, and nanoscale pore structures of a ~10‐μm‐long porous IDP, consisting of two types of voids that are interconnected in 3‐D space. One is morphologically primitive and mostly submicron‐sized intergranular voids that are ubiquitous; the other is morphologically advanced and well‐defined intragranular nanoholes that run through the approximate centers of ~0.3 μm or lower submicron hollow grains. The distinct hollow grains exhibit complex 3‐D morphologies but in 2‐D projections resemble typical organic hollow globules observed by transmission electron microscopy. The particle, with its outer region characterized by rough vesicular structures due to thermal alteration, has turned out to be an inherently fragile and intricately submicron‐ and nanoporous aggregate of the sub‐μm grains or grain clumps that are delicately bound together frequently with little grain‐to‐grain contact in 3‐D space.

Tensile failure observations in sintered steel foam struts revealed by sub-micron contrast-enhanced microtomography

Powder metallurgical open-cell steel foams made of hollow struts are of great interest for impact resistance. Here we report experimental results of high-resolution characterisation of single struts, extracted from a commercially available steel foam. Synchrotron radiation X-ray microtomography reveals that the hollow struts are made of triplets of lens shaped rods, connected to each other along the long axis, appearing triangular in cross-sections. The struts have a non-uniform geometry and they include macro and micropores as well as high-density inclusion powder particles, poorly fused with the matrix. Micro-tensile testing showed that tensile failure is accompanied by longitudinal unzipping due to shear along the thinner material found near the hollow corners. Included, higher-density powder particles deflect crack propagation along the interface with the matrix, where much porosity is observed. Results of finite element simulations well match our mechanical tests, revealing plastic deformation due to bending and significant shear stresses arising between neighbouring rods within the same strut. The failure behaviour and the mechanical response of sintered struts in steel foams produced using non-uniformly coated polyurethane templates is the result of an interplay between the triplet geometry, sub-micron pores, precipitates and high-density inclusions.

Sub-micron fracture mechanism in silica-based glasses activated by permanent densification from high-strain loading

Several silica-based glasses were fractured at high strain energy via drop-weight testing on small specimens. A cylindrical specimen geometry was chosen to promote initially simple, axisymmetric, and uniform compressive loading. The imposed uniaxial compressive strain at impact was sufficiently high to qualitatively cause permanent densification. Produced fragments were collected for postmortem and a fraction of them, for all the silica-based glasses, consistently had distinct sub-micron-sized fractures (~300–1000nm), designated here as “microkernels”, on their surfaces. They would most often appear as a sub-micron pore on the fragment - apparently if the microkernel had popped out as a consequence of the local crack plane running through it, tensile-strain release, and the associated formation of the fragment it was on. No fractographic evidence was found to show the microkernels were associated with local failure initiation. However, their positioning and habit sometimes suggested they were associated with localized crack branching and that they could have influenced secondary fracturing that occurred during overall crushing and comminution and associated fragment size and shape creation. The size range of these microkernels is much too small to affect structural flexure strength of these glasses for most applications but are of a size and concentration that may affect their ballistic, shock, crush, and comminution responses when permanent densification is concomitantly occurring.

Electrochemical accessibility of porous submicron MnO2 spheres as active electrode materials for electrochemical capacitors

The electrochemical utilization of various submicron amorphous manganese dioxide spheres (SMnO2) with highly controlled shape and size was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. MnO2 spheres were synthesized by reaction between KMnO4 and 1–butanol in aqueous butyric acid solution at room temperature. Particle size was tuned by adjusting the concentration of KMnO4. The materials were characterized by X-ray diffraction, scanning electron microscopy, dynamic light scattering and nitrogen gas adsorption measurements. SEM results reveal that spheres with average diameter of 451±9, 218±12 and 195±85nm were produced by using a 20, 8 and 2mM of KMnO4 solution, respectively. DLS measurements showed similar mean particle diameter with a relatively high polydispersity-index that indicates the presence of larger agglomerated particles. The BET surface area of the three SMnO2 is ranging between 216 and 259m2g−1. Since very similar specific capacitance values of about 200Fg−1 (per active material mass) at 2mVs−1 were found for all three samples, MnO2 electrochemical utilization is more related to the pore size distribution rather than the particle size.

Ultrasonically assisted fabrication of vaterite submicron-sized carriers

Ultrasonically accomplished precipitation of calcium carbonate was demonstrated as a novel beneficial method for the formation of porous submicron vaterite particles with low dispersity, high mass yield, and the “scaling up” possibility. The effect of sonication on the size and crystallographic phase of formed particles was investigated by comparing this method with a magnetic stirring and non-stirring interfusion. By virtue of their porosity, vaterite particles allow the different substance incorporation. The loading properties of synthesized particles were demonstrated for high molecular weight substance (labeled protein), as well as for low molecular one (fluorescent dye). Such features open up perspectives of drug encapsulation and delivery for the vaterite submicron carriers.

Reparable Cell Sonoporation in Suspension: Theranostic Potential of Microbubble.

The conjunction of low intensity ultrasound and encapsulated microbubbles can alter the permeability of cell membrane, offering a promising theranostic technique for non-invasive gene/drug delivery. Despite its great potential, the biophysical mechanisms of the delivery at the cellular level remains poorly understood. Here, the first direct high-speed micro-photographic images of human lymphoma cell and microbubble interaction dynamics are provided in a completely free suspension environment without any boundary parameter defect. Our real-time images and theoretical analyses prove that the negative divergence side of the microbubble's dipole microstreaming locally pulls the cell membrane, causing transient local protrusion of 2.5 µm in the cell membrane. The linear oscillation of microbubble caused microstreaming well below the inertial cavitation threshold, and imposed 35.3 Pa shear stress on the membrane, promoting an area strain of 0.12%, less than the membrane critical areal strain to cause cell rupture. Positive transfected cells with pEGFP-N1 confirm that the interaction causes membrane poration without cell disruption. The results show that the overstretched cell membrane causes reparable submicron pore formation, providing primary evidence of low amplitude (0.12 MPa at 0.834 MHz) ultrasound sonoporation mechanism.

Elastic Properties of Protein Functionalized Nanoporous Polymer Films.

Retaining the conformational structure and bioactivity of immobilized proteins is important for biosensor designs and drug delivery systems. Confined environments often lead to changes in conformation and functions of proteins. In this study, lysozyme is chemically tethered into nanopores of polystyrene thin films, and submicron pores in poly(methyl methacrylate) films are functionalized with streptavidin. Nanoindentation experiments show that stiffness of streptavidin increases with decreasing submicron pore sizes. Lysozymes in polystyrene nanopores are found to behave stiffer than the submicron pore sizes and still retain their specific bioactivity relative to the proteins on flat surfaces. Our results show that protein functionalized ordered nanoporous polystyrene/poly(methyl methacrylate) films present heterogeneous elasticity and can be used to study interactions between free proteins and designed surfaces.

Tuning Microparticle Porosity during Single Needle Electrospraying Synthesis via a Non-Solvent-Based Physicochemical Approach

Porous materials, especially microparticles (MP), are utilized in almost every field of engineering and science, ranging from healthcare materials (drug delivery to tissue engineering) to environmental engineering (biosensing to catalysis). Here, we utilize the single needle electrospraying technique (as opposed to complex systems currently in development) to prepare a variety of poly(ε-caprolactone) (PCL) MPs with diverse surface morphologies (variation in pore size from 220 nm to 1.35 µm) and architectural features (e.g., ellipsoidal, surface lamellar, Janus lotus seedpods and spherical). This is achieved by using an unconventional approach (exploiting physicochemical properties of a series of non-solvents as the collection media) via a single step. Sub-micron pores presented on MPs were visualized by electron microscopy (demonstrating a mean MP size range of 7–20 μm). The present approach enables modulation in morphology and size requirements for specific applications (e.g., pulmonary delivery, biological scaffolds, multi-stage drug delivery and biomaterial topography enhancement). Differences in static water contact angles were observed between smooth and porous MP-coated surfaces. This reflects the hydrophilic/hydrophobic properties of these materials.

Deformation modeling of polyvinylidenedifluoride (PVDF) symmetrical microfiltration hollow-fiber (HF) membrane

The tensile deformation behavior of polyvinylidenedifluoride (PVDF) symmetrical microfiltration hollow-fiber (HF) membranes was studied. The membranes had submicron pores with a three-dimensional open-cell structure. The surface and cross section of the porous membranes were observed by FESEM (field emission scanning electron microscope) to investigate the microstructure of the cell, namely, its size and ligament geometry. During uniaxial tensile tests, the membranes underwent elastic deformation and plastic deformation. Large deformation induced pore growth along the tensile direction, resulting in an increase in water permeability. In order to establish a mechanical model for tensile deformation, the finite element method (FEM) was employed. In this model, the Kelvin polyhedron (truncated octahedron structure) was used to mimic a three-dimensional open-cell structure. A one-unit cell based on this structure was created, and a periodical boundary condition was employed for the FEM computation. The FEM model could reproduce the overall elastoplastic deformation behavior of the porous membrane and provide useful insight into the fabrication of porous membranes and reliable operation of water purification.

Experimental investigation of the pore structure characteristics of the Garau gas shale formation in the Lurestan Basin, Iran

Gas storage and flow characteristics of shale gas reservoirs are greatly affected by their complex pore structure. These structures contain a wide range of pore size distribution with significant contribution of nanometer scaled pores. In this work an integrated experimental approach including geochemical and mineralogical analysis, Mercury Injection Capillary Pressure (MICP) and helium expansion porosimetry along with nano-scale Field Emission-Scanning Electron Microscopy (FE-SEM) imaging techniques was used to characterize pore structure of Garau formation, a shale gas play recently explored in the western Iran.MICP was used in this study as an acceptable laboratory method to identify pore throat size down to three nanometers. FE-SEM image analysis was also applied for better understanding of distribution, connectivity and nature of sub-micron pore systems. Experimental measurements were made on 23 plugs collected from two depth intervals from two wells in the Garau formation. X-Ray Diffraction mineralogy (XRD) analysis represents that shale samples are calcite rich with low clay contents. The kerogen analysis shows kerogen type II with Total Organic Carbon (TOC) values ranging from 0.41 to 3.18%. The total porosity obtained from helium expansion test, varies between 0.1 and 3.6% under ambient test conditions and between 0.1 and 1.2% under overburden stress test conditions suggesting high stress dependency of the porosity in the studied samples. Based on the MICP test results, the pore throat sizes in the Garau shale samples belong to the mesopores and macropores realm. In addition, two types of pore size distributions are observed in the samples according to their mineralogical compositions. The majority of pores in the first group with high calcite contents are in macro-scale (>50 nm) with the dominant pore radius of around 50 μm, while the dominating pore radii in the second group with illite traces are found to be in the meso-scale (5–50 nm). Furthermore, comparing the MICP and helium porosimetry test results shows that the total porosity of the Garau shale increases with the increase of the meso-scale pore volume. Observations from FE-SEM images were also in good agreement with MICP test results. FE-SEM analysis revealed that pores are located both in the organic matter and inorganic matrix whether in isolated or interconnected types. These observations showed that a portion of kerogen body is occupied by nano-scaled pores with different shapes and sizes; as a result, samples with higher TOC contents and maturity offers generally higher total porosity values.

Facile Synthesis of Rod–Coil Block Copolymers with Chiral, Helical Polycarbodiimide Segments via Postpolymerization CuAAC “Click” Coupling of Functional End Groups

Using the living nickel(II)-mediated polymerization of carbodiimides, the chiral (R)- or (S)-N-1-phenethyl-N′-methylcarbodiimide (PMC) monomers were polymerized with a new TIPS protected alkyne functional nickel initiator forming PPMC with an excess single-handed screw sense and the alkyne moiety covalently attached to the terminus of the polymer, as confirmed by 1H NMR and MALDI-TOF MS. After deprotection, the alkyne end groups of rigid-rod PPMC-2 were coupled with azide-terminated, random-coil PS and PEG homopolymers forming a novel class of helical-b-coil block copolymers. In the thin-film, all synthesized diblock copolymers formed interesting nanofibular morphologies when subject to specific conditions. The triblock RCP-4, however, adopted unique macroporous morphology as identified by AFM and SEM with average pore diameters of ca. 832 ± 194 nm. The origin of this was found to be associated with the ordering of large, hollow vesicle aggregates upon solvent evaporation followed by the melting of these aggregates filling in the hollow interior forming the submicron pores observed. Furthermore, the size of these aggregates can be easily modulated in a linear fashion from 272 to 1648 nm simply by increasing the concentration of RCP-4 in THF. Finally, the three PPMC–PEG copolymers synthesized were found to adopt lyotropic cholesteric mesophases in concentrated toluene solutions (ca. 30 wt %).

Thermochemical investigation of the water uptake behavior of MgSO4 hydrates in host materials with different pore size

The reversible dehydration and re-hydration of salts is considered as a promising thermochemical process for the storage of heat from a renewable energy source such as solar energy. Such materials would help to overcome the gap between demand of energy and supply from renewable sources. So far however, attempts to make full use of the very high storage densities of salt hydrates were unsuccessful, largely due to problems with the kinetics of the hydration and dehydration reactions. In the present work, in order to overcome these problems, magnesium sulfate was embedded in various porous host materials with average pore diameters (dm) ranging from 1.7μm to 7nm. The dehydration and water uptake behavior of these composites was investigated by thermogravimetry and isothermal calorimetry. The heat of reaction of the composites at 85% RH and 30°C varies from 103MJ/m3 in glass frits (dm=1.7μm) to 556MJ/m3 in porous glass (dm=7nm) and increases with decreasing pore size. The contribution of the heat of hydration to the overall thermal effect decreases with decreasing pore size while the contribution of the heat of adsorption increases. In bulk samples and in glass frits with coarse, micron-sized pores, MgSO4·6H2O is the major hydration product. In host materials with submicron pores, water vapor uptake yields both a crystalline hydrated phase (most likely MgSO4·7H2O) and its saturated solution. Apart from pore size, the salt content of the porous substrate, i.e., the degree of pore filling, is another critical parameter affecting the overall heat of reaction. Pore size and pore filling as well as porosity are the most important parameters that need to be optimized in order to achieve high storage densities with composite materials of a porous host materials and embedded salt hydrates.