Elliptical Pores Research Articles

A Corrole‐Based Covalent Organic Framework Featuring Desymmetrized Topology

AbstractHerein, for the first time, we present the successful synthesis of a novel two‐dimensional corrole‐based covalent organic framework (COF) by reacting the unusual approximately T‐shaped 5,10,15‐tris(p‐aminophenyl)corrole H3TPAPC with terephthalaldehyde, which adopts desymmetrized hcb topology and consists of a staggered AB stacking structure with elliptical pores. The resultant corrole‐based COF, TPAPC‐COF, exhibits high crystallinity and excellent chemical stability. The combination of extended π‐conjugated backbone and interlayer noncovalent π–π interactions endows TPAPC‐COF with excellent absorption capability in the entire visible‐light and even near‐infrared regions. Moreover, this work suggests the promise of TPAPC‐COF as a new class of photoactive material for efficient singlet‐oxygen generation with potential photodynamic therapy application as demonstrated by in vitro anticancer studies.

A Corrole-Based Covalent Organic Framework Featuring Desymmetrized Topology.

Herein, for the first time, we present the successful synthesis of a novel two-dimensional corrole-based covalent organic framework (COF) by reacting the unusual approximately T-shaped 5,10,15-tris(p-aminophenyl)corrole H3 TPAPC with terephthalaldehyde, which adopts desymmetrized hcb topology and consists of a staggered AB stacking structure with elliptical pores. The resultant corrole-based COF, TPAPC-COF, exhibits high crystallinity and excellent chemical stability. The combination of extended π-conjugated backbone and interlayer noncovalent π-π interactions endows TPAPC-COF with excellent absorption capability in the entire visible-light and even near-infrared regions. Moreover, this work suggests the promise of TPAPC-COF as a new class of photoactive material for efficient singlet-oxygen generation with potential photodynamic therapy application as demonstrated by in vitro anticancer studies.

Preparation of the crosslinked GO/PAA aerogel and its adsorption properties for Pb(II) ions

The graphene oxide(GO)/polyacrylic acid(PAA) was prepared by in situ polymerization in graphene oxide lamellae, and crosslinked graphene oxide/polyacrylic acid complex(CLGO/PAA) was formed by esterification reaction between 1,4-butanediol and carboxylic acid of PAA at same time. The CLGO/PAA aerogel was prepared by freeze drying method. The CLGO/PAA aerogel has good stability and high saturated adsorption capacity for the adsorption of Pb(II) ions in water. The structure and properties of the CLGO/PAA aerogel were characterized by using x-ray diffractometry(XRD), field emission scanning electron microscopy (FESEM), infrared spectroscopy(FT-IR), and atomic absorption spectrometer(AAS), respectively. The results show that the prepared CLGO/PAA aerogel possess elliptical pore structure. In addition, the adsorption properties of the CLGO/PAA aerogel for Pb(II) in water were studied under different pH, different concentrations of Pb(II), contact time and number of adsorbent cycles. The results show that the adsorption amount of Pb(II) could reach to 640 mg g−1 at the initial concentration of Pb(II) was 500 mg l−1, and the adsorption equilibrium could be reached after 60 min. The adsorption amount for Pb(II) was still 143 mg g−1 after 5 times cycle.

Deformation of organic matter and its effect on pores in mud rocks

Pores within organic matter (OM) are strongly linked to hydrocarbon generation and primary migration in fine-grained source rocks and are very important for evaluating hydrocarbon storage and flow in shale reservoirs. Thus, it is critical to clarify the features of OM-hosted pores and their evolution in organic-rich mud rocks. The OM in mud rocks, including kerogen and bitumen, is deformed when the original equilibrium stress conditions are altered. The OM deformation at the nano- or microscale has rarely been discussed because of the lack of unequivocal evidence. This research begins with examining the subsurface evolution of kerogen and bitumen, with emphasis on various features of pores hosted by bitumen. Evidence of OM deformation is documented in scanning electron microscope images of seven overmature samples from the lower Silurian Longmaxi Shale, Sichuan Basin. To aid in the understanding and analysis, OM deformation is classified into three types: type I deformation induced by one additional force, type II deformation induced by two additional forces acting on two locations of single OM particles, and type III deformation induced by three or more deforming forces acting at three or more locations of single OM particles. Thus, type I deformation is generally less complex than type II and III deformation. The OM particles subjected to type I deformation were analyzed quantitatively for parameters such as pore size, geometry, and long-axis orientation of elliptical pores. Deformation of OM enhances the robust heterogeneity of OM-hosted pores.

Effects of pore morphology and pore edge termination on the mechanical behavior of graphene nanomeshes

We report results of a systematic computational study on the mechanical response of graphene nanomeshes (GNMs) to uniaxial tensile straining based on molecular-dynamics simulations of dynamic deformation tests according to a reliable bond-order interatomic potential. We examine the effects on the GNM mechanical behavior under straining along different directions of the nanomesh pore morphology and pore edge passivation by testing GNMs with elliptical pores of various aspect ratios and different extents of edge passivation through termination with H atoms of under-coordinated edge C atoms. We establish the dependences of the ultimate tensile strength, fracture strain, and toughness of the GNMs on the nanomesh porosity, derive scaling laws for GNM strength-density relations, and find the GNMs' mechanical response to uniaxial straining to be anisotropic for pore morphologies deviating from circular pores. We also find that the GNM tensile strength decays exponentially with increasing GNM porosity and that pore edge termination with H atoms causes a reduction in the GNMs' elastic stiffening, strength, deformability, and toughness; this hydrogen embrittlement effect is more pronounced at a high level of pore edge passivation that renders the edge C atoms sp3-hybridized. The underlying mechanisms of crack initiation and propagation and nanomesh failure for the various types of GNMs examined also are characterized in atomistic detail. Overall, even highly porous GNMs remain particularly strong and deformable and, therefore, constitute very promising 2D mechanical metamaterials.

Mechanical properties of honeycomb nanoporous silicon: a high strength and ductile structure

There are remarkable studies geared towards developing mechanical analysis of nanoporous structures, while the size effect has been a major concern so far to improve strength or deformability. In this study, molecular dynamics simulations are utilized to study the pore shape effect on the mechanical behaviour of nanoporous silicon with circular, elliptical, square and hexagonal pore shapes. The influence of pore configuration on load transfer capabilities is studied for nanoporous silicon. A distinguished set of mechanical properties is observed on silicon with a hexagonal pore shape—resembling a honeycomb structure—with a high tensile strength and toughness. The study exhibits an improvement in the ductility through unique stress transformation in the hexagonal pore shape. In addition to the relative density, the potential to control the mechanical properties is demonstrated through the hexagon angle. Finally, a scaling law is developed for the mechanical behaviour of honeycomb nanoporous silicon. In addition to their outstanding mechanical properties, the work provides further insight into the capability of nanoporous structures in sensing applications due to their high surface-to-volume ratios.

Effect of lithofacies on the pore system of over-mature Longmaxi shale in the Jiaoshiba area, Sichuan Basin, China

Abstract Ten Longmaxi shale samples were collected from the Jiaoshiba area, China, where 5 billion cm 3 /year of shale gas is produced. The samples were evaluated to characterize the pores of various shale lithofacies. Three shale lithofacies were determined in the Jiaoshiba area, Sichuan Basin, China, based on the shale mineral components, namely, siliceous lithofacies (SL), argillaceous lithofacies (AL), and mixed lithofacies (ML). Field emission scanning electron microscopy (FE-SEM), which was performed under high and low voltages, GRI porosity, and carbon dioxide and nitrogen adsorptions were used to investigate the bulk-shale porosity, pore type, pore size, pore morphology, and pore volume among the lithofacies. Lithofacies affects the shale total organic carbon (TOC), bulk-shale porosity, pore size, shape, and volume. SL and ML contain high porosity, high TOC, abundant organic-matter (OM)-hosted pores, and high OM porosity, whereas AL contains few OM pores and has low TOC and low porosity. In the same lithofacies, samples with various TOC values exhibit different pore morphologies. For SL, the low-TOC sample has a round and elliptical OM pore forms, whereas the high-TOC samples show linear and narrow pore shapes that are probably associated with gas expulsion. In ML, the higher TOC is related to spherical or near-spherical OM pores, whereas the OM pore shape collapses in the low-TOC shale. Therefore, lithofacies affect the shale reservoir, and the characteristic and evolution of OM pores should be considered as constraints in shale lithofacies. In SL, sections with a higher TOC value are prime targets despite the high expulsion efficiency, which does not affect the enrichment and high yield of the shale gas. Sections of ML and low-TOC SL should be considered as potential targets because of higher OM porosity and low expulsion efficiency, whereas sections of AL engender risk in exploration and development of shale gas.

Improving ductility of nanoporous metallic glasses

It is reported that enhanced ductility can be achieved in metallic glasses (MGs) by proper introduction of pores. To design MGs with better ductility, it is important to elucidate the pore effects on the ductility and failure mechanisms. In this paper, tensile deformation behaviors of nanoporous MGs with elliptical and circular pores are studied by large scale molecular dynamics (MD) simulations. The influences of pore aspect ratio and porosity on the failure stains are investigated. It is found that as the aspect ratio increases the failure strain first increases to reach a maximum value and then decreases. For a given aspect ratio, the failure strain of the porous MGs increases as the porosity decreases. The corresponding mechanisms are revealed via the microstructure evolutions in the simulations. The results can be used to improve the ductility of MGs.

Manufacturing of porous aluminum 2024 alloy samples with impressive compression properties

In the present work; nanocrystalline porous aluminum samples are manufactured using reactive spray atomization following an efficient procedure. The samples showed the best specific energy absorption density value in compression for aluminum on densification close to 0.06 MJ kg−1 at quasistatic loading, which is the best-recorded value for a bulk material according to authors knowledge. The reasons for such high compression plastic properties are due to a nano-sized intermetallic phase Al2Cu and nano stringers Al2O3 located on the walls of elliptical shape thick wall pores. The aforementioned structural features increased the strength for these samples and enabled absorption of high energy more than other materials. The high performance of the prepared samples and the cheapness of the present method can open new horizons for aerospace and automotive aluminum industries.

Computational screening of zeolites for C3H7Cl/C3H5Cl separation and a conformation based separation mechanism

The separation of alkanes-olefins plays an essential role in petrochemical industry and is also challenging because of their similar physicochemical properties, especially for halogenated alkanes-olefins mixtures. In this work, we quickly screened a series of zeolites to separate 1-chloropropane/allyl chloride (C3H7Cl/C3H5Cl) mixture by molecular simulation. The results show that zeolites with specific pore geometry (e.g., AHT type) only adsorb C3H5Cl thus C3H5Cl can be selectively separated from C3H7Cl completely. These zeolites have one-dimensional elliptical pores with similar sizes, which match with the low energy conformation of C3H5Cl. The flux data of membrane based on these zeolites were also investigated, which confirmed that they can separate C3H7Cl and C3H5Cl with an ultrahigh selectivity. Based on the thermodynamics analysis, we proposed a pore geometry based conformation recognition mechanism of this special adsorption and separation phenomena. In conclusion, this paper provides an avenue to design or screen nano-porous materials for alkanes-olefins separation.

Organic nanopore structure and fractal characteristics of Wufeng and lower member of Longmaxi shales in southeastern Sichuan, China

Abstract Organic nanopores in shale gas reservoirs are the main storage space for free gas and adsorbed gas and directly affect the occurrence mode and movement of shale gas. In this study, field emission-scanning electron microscopy (FE-SEM), low-pressure gas (N2 and CO2) adsorption and mercury injection capillary pressure (MICP) analyses were performed and interpreted with statistical and fractal analyses to investigate the organic pore structure in the Upper Ordovician Wufeng shale (O3w) and the Lower Silurian lower member of Longmaxi shale (S1l). It was found that organic pores in 15 samples from 8 layers of the Wufeng-Longmaxi shale section are usually developed in discrete organic matter particles, organic matter associated with clay minerals and organic matter associated with pyrite framboids. The size, shape and quantity of organic pores vary greatly. The organic pores in Wufeng Formation (layer 1) are densely developed in organic matter particles with relatively small sizes and irregular shapes. The organic pores in the lower part of the lower member of Longmaxi Formation (layers 3, 4 and 5) are less developed and have relatively larger pore sizes with an elliptical shape. In contrast, the organic pores in the upper part of the lower member of Longmaxi Formation (layers 6, 7, 8 and 9) are the least developed, with elliptical shapes and pore sizes in between the two cases above. A higher value of fractal dimension refers a more complex form and this value of whole organic pores with full range of sizes (Dwop) is the largest and followed by organic macropores (Dop>50), organic pores with pore sizes between 4 nm and 50 nm (Dop4-50), and organic pores with pore sizes less than 4 nm (Dop

Four new Amynthas and Metaphire earthworm species from nine provinces in southern China.

Four new species belonging to genera Amyntha and Metaphire were discovered from an extensive area in southern China, covering the provinces Sichuan, Yunnan, Guizhou, Guangdong, Guangxi, Fujian, Hunan, Jiangxi and Anhui. The species are named Amynthas dispersus Sun Qiu, sp. nov., Amynthas shanghangensis Sun Qiu, sp. nov., Amynthas dentiformis Sun Jiang, sp. nov. and Metaphire sanmingensis Sun Jiang, sp. nov. The first two new species have four pairs of intersegmental spermathecal pores in 5/6-8/9. A. dispersus has elliptical and glandular male pore porophores raised on a low pad-like area surrounded by two to three shallow skin folds, the genital papillae are variable in the spermathecal pore and male pore regions, and prostate glands are vestigial or rudimentary. Amynthas shanghangensis has male porophores surrounded by three papillae, each prostate gland accompanied by an accessory gland, and the distal ½-⅓ of the spermathecal diverticulum dilated into a rod-shaped seminal chamber. Amynthas dentiformis has two pairs of spermathecal pores in 7/8-8/9, male pores always surrounded by two papillae, and small sacs on the dorsal and ventral margins of the intestinal caecae; the prostate gland occasionally has stalked accessory glands. M. sanmingensis is in the Metaphire houlleti-group, and has secondary male pores opening to copulatory pouches, rod-shaped spermathecal seminal chamber, as well as variable genital papillae in spermathecal and male pores regions. The GenBank accession numbers of DNA barcode data are attached under the description of each species.

Theoretical Study of Nanoporous Graphene Membranes for Natural Gas Purification

Gas filtration by means of membranes is becoming increasingly important for industrial processes due to its low cost. In particular, membranes can be applied to separate methane in natural gas from pollutants such as hydrogen sulfide and carbon dioxide. The recent advent of nanoporous graphene as material for membranes helped to overcome the current problems of polymeric membranes, namely the permeability/selectivity tradeoff. However, the factors that determine gas filtration through nanoporous graphene are not completely clear yet. In this work, we show that pore size, shape and functionalization severely affect the selectivity of the membrane toward CO 2 and H 2 S with respect to CH 4 . We identified that the critical diameter of circular pore for the separation of contaminants from methane with graphene membranes is 5.90 Å. An elliptical pore is discovered to select gas species having similar sizes on the basis of their shape. The more elongated CO 2 is allowed to pass though the pore while the more spherical H 2 S and CH 4 are rejected. Finally, the gas-membrane interactions are found to decisively affect the filtration performances. Functionalization with hydroxyl groups led to a higher permeability of the gas species with polar bonds while keeping an excellent selectivity.

Influence of random pore defects on failure mode and mechanical properties of SiC ceramics under uniaxial compression using discrete element method

To investigate the relationship between micro-defects in ceramic materials and macro mechanical properties and behaviours, a computational model of SiC ceramics with randomly oriented elliptical pores was established using the discrete element method (DEM). The effects of pore defect content and its aspect ratio on the failure mode, stress-strain curve and mechanical properties of specimen were investigated under uniaxial compression. The effective Young's modulus which was obtained from DEM simulations was compared with the predictions of Mori-Tanaka scheme (MTS) and Self-Consistent scheme (SCS) at various pore defect densities. The results showed that the compressive strength and crack initiation stress decrease nonlinearly as the pore defect content increases. Furthermore, the smaller the aspect ratio of the elliptical pore defects was, the more obvious the weakening trend was. As the pore defect content increases, the failure mode of the specimen changed from brittle fracture to tensile-shear mixing and then to axial splitting. The stress-strain curves showed a certain “softening” period during the loading process. The effective Young's modulus obtained from the DEM simulations coincides with the approximations of MTS and SCS at low pore densities. However, when the pore defect density became larger, the DEM simulation results were slightly lower than the theoretical results of the Mori-Tanaka scheme, which only considers the weak interaction between defects.

Strengthening mechanisms in nanoporous metallic glasses

It has been shown that metallic glasses (MGs) can have enhanced ductility by properly introduced pores. However, the pore effects on the yield strength and the underlying mechanisms have yet to be fully clarified. In this paper, nanoporous MGs with regularly distributed elliptical pores are investigated by large scale molecular dynamics simulations. Obtained results show that, when increasing the semi-axis a in the loading direction and fixing the other semi-axis b of the pores, the strength of the nanoporous MGs increase firstly to reach a maximum value and then decreases. It is found that the porosity and pore shape are the main factors affecting the strength. For a given porosity, the yield strength increases first and then approaches an asymptotic value with increasing a. The underlying mechanism is that the shear bands transit from localization to spreading. For a given pore shape, the yield stress decrease with increasing a. And this is because the increase of porosity leads to reduction in strength. Due to the above mechanisms, there exists a maximum strength at a critical size where the shear band evolution transition occurs. A model for the critical size of acri is proposed to predict the maximum strength.

Rational Design of Two-Dimensional Hydrocarbon Polymer as Ultrathin-Film Nanoporous Membranes for Water Desalination.

Membrane-based water desalination has drawn considerable attention for its potential in addressing the increasingly limited water resources, but progress remains limited due to the inherent constraints of conventional membrane materials. In this work, by employing state-of-the-art molecular simulation techniques, we demonstrated that two-dimensional hydrocarbon polymer membranes, materials that possess intrinsic and tunable nanopores, can provide opportunities as molecular sieves for producing drinkable water from saline sources. Moreover, we identified a unique relationship between the permeation and selectivity for membranes with elliptical pores, which breaks the commonly known trade-off between the pore size and desalination performance. Specifically, increase in the area of elliptical pores with a controlled minor diameter can offer an improved water flux without compromising the ability to reject salts. Water distributions and water dynamics at atomic levels with the potential of mean force profiles for water and ions were also analyzed to understand the dependence of permeation and selectivity on the pore geometry. The outcomes of this work are instrumental to the future development of ultrathin-film reverse osmosis membranes and provide guidelines for the design of membranes with more effective and efficient pore structures.

H2/CH4 Gas Separation Using Graphene Drilled With Elliptical Pores

Previous studies have considered nanoporous graphene (NPG) drilled with circular/regular pore, and have shown that only pore-10 is H2 selective. However, the hydrogen permeance through this pore is low, meaning that the hydrogen yield is low. In order to extend the selectivity range, we considered pores of elliptical/irregular geometries. Using molecular dynamics simulations, we simulated pores-10 to 20, all with a very elongated geometry, and have shown that these pores exhibit large H2 permeance and negligible CH4 permeances. This implies that these pores produce large hydrogen selectivity with high hydrogen yields. Thus, an NPG membrane designed in this manner could revolutionize hydrogen separation in the industry, by providing a more efficient and environmentally friendly method.

Monitoring the osseointegration process in porous Ti6Al4V implants produced by additive manufacturing: an experimental study in sheep.

This study investigated the design and osseointegration process of transitive porous implants that can be used in humans and all trabecular and compact bone structure animals. The aim was to find a way of forming a strong and durable tissue bond on the bone-implant interface. Massive and transitive porous implants were produced on a direct metal laser sintering machine, surgically implanted into the skulls of sheep and kept in place for 12 weeks. At the end of the 12-week period, the Massive and porous implants removed from the sheep were investigated by scanning electron microscopy (SEM) to monitor the osseointegration process. In the literature, each study has selected standard sizes for pore diameter in the structures they use. However, none of these involved transitional porous structures. In this study, as opposed to standard pores, there were spherical or elliptical pores at the micro level, development channels and an inner region. Bone cells developed in the inner region. Transitive pores grown gradually in accordance with the natural structure of the bone were modeled in the inner region for cells to develop. Due to this structure, a strong and durable tissue bond could be formed at the bone-implant interface. Osseointegration processes of Massive vs. porous implants were compared. It was observed that cells were concentrated on the surface of Massive implants. Therefore, osseointegration between implant and bone was less than that of porous implants. In transitive porous implants, as opposed to Massive implants, an outer region was formed in the bone-implant interface that allowed tissue development.

Characterization of organic matter pores in typical marine and terrestrial shales, China

Organic matter (OM) is a significant component in shale and controls gas storage and transportation. Typical marine (JLD sample, NTT sample, WF sample and LMX sample) and terrestrial (C7 sample) OM-rich shale samples from the Sichuan Basin and Erdos Basin in China were investigated using X-ray diffraction and scanning electron microscopy (SEM) to study their mineralogy and OM pore network properties. The X-ray diffraction results indicated that the content of brittle minerals (quartz, plagioclase, calcareous dolomite, dolomite and pyrite) in each shale sample was higher than 60%, providing material in which original matrix pores and microfractures formed during an early stage of diagenesis. The types and contents of clay minerals vary among the shale samples. The main clay mineral in most of the marine shale samples is illite, but the primary clay in the terrestrial shale is an illite–smectite mixed layer. The maturity data of the OM in the marine shale samples suggested a moderate to high stage of maturity, while the terrestrial shale was collected at a relatively low stage of thermal evolution. The SEM observations suggested that the OM was either tight or porous, and the former was the dominant state. The OM pores preserved in the shale consisted of pores within, between and at the interfaces of the OM particles. For the OM pores within the OM particles, the most dominant pore type, type I, exhibits honeycomb-like pores formed by hydrocarbon generation; this type of pore is most developed in the marine LMX shale and NTT shale. Pore type II is related to biogenic residue and is more developed in the JLD shale and LMX shale. Pore type Ⅲ includes mainly elliptical pores or microcracks related to the volume loss of bitumen. The OM pores between the OM particles are narrow and laminar; these structures were inherited from the previous clay mineral structures. The OM pores at the interfaces of the OM particles and the mineral grains are usually observed as microfractures and are more developed in the C7 shale. The lack of pores within the OM in the terrestrial C7 shale was due to low maturity. A combination of SEM results, mineral compositions and carbon analyses indicated a positive correlation between the development of OM pores and the organic carbon content, as well as the thermal maturity. With increasing burial and maturity, migrated OM was squeezed into mineral matrix pores and appears to be continuous, especially along the bedding planes, forming an effective network due to the interconnectivity of the OM.

A facile method of preparing highly porous polylactide microfibers

ABSTRACTHighly porous polylactide (PLA) microfibers with the diameter of about 14 µm are prepared by melt‐spinning and stretching core–sheath PLA fibers (CSF) and sequent treatment of ethyl acetate. The resultant pores are regular and elliptical. The average values of length of major axis and minor axis of elliptical pores are around 1 and 0.5 μm, respectively. This new and facile method can prepare porous PLA fibers on industrial scale, and nearly overcome all the shortcomings of melt‐spinning and stretching method. In addition, highly porous structure in partially oriented poly(l‐lactide) yarn (POY) can be also formed by treating POY using ethyl acetate. The obtained pores are irregular. In addition, the formation mechanism of pore structure in CSF is different with the one in POY. The former is the separation of row‐nucleated lamellae induced by stretching while the latter is swelling and subsequent solvent‐induced crystallization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45860.