Elliptical Pores Research Articles

Float-Cast Microsieves with Elliptical Pores.

Polymeric microsieves bearing elliptical pores were successfully prepared via float-casting: a dispersion comprising nonvolatile acrylate monomers and ellipsoidal polystyrene particles was spread onto a water surface. The resulting self-organized monolayer was laterally compressed, and the monomer was photopolymerized, giving rise to a membrane comprising ellipsoidal particles laterally embedded in a 0.5 μm thin polymer membrane. The particles were dissolved, leaving behind elliptical pores. These pores had an average length of the major axis of 0.87 ± 0.1 μm and of the minor axis of 0.42 ± 0.07 μm and an aspect ratio of approximately 2. The microsieve bearing these submicrometric elliptical pores was transferred to a hierarchical structure made out of microsieves bearing circular pores of 6 μm diameter on top of a microsieve with 70 μm diameter pores. The resulting hierarchically structured microsieve had a porosity of 0.13. At a pressure difference of typically 103 Pa (Reynolds number aprox. 0.002), the volumetric permeance for water was Pe = /A/Δp = 0.5·10-6 m/s/Pa, the product viscosity·permeance is η·/A/Δp = 0.5·10-9 m. This value is lower than the corresponding values of microsieves with circular pores of similar diameter produced by the same technique. The beneficial effects of higher permeance per pore caused by the elliptical shape are countered by lower porosity caused by less efficient packing of the ellipsoidal particles.

Porous dielectric design for high-performance flexible shear sensors

Abstract Flexible sensors, renowned for their exceptional adaptability, are widely utilized in areas such as robotics and healthcare monitoring. Currently, understanding the relationship between the structure and performance of flexible shear sensors has become increasingly important. In this study, the structural characteristics of porous flexible shear sensors and their impact on performance were analyzed using Finite Element Method (FEM). The investigation focused on three factors: porosity, pore size, and the shape of elliptical pores. The findings suggest that augmenting the porosity substantially boosts the shear sensitivity of the sensor, whereas the pore size exerts a relatively minor influence on sensitivity. Furthermore, compared to circular ones, elliptical pores can further increase the shear sensitivity of the sensor, particularly when the ellipse’s major axis is oriented horizontally. These findings are of significant reference value for designing and optimizing high-performance flexible shear sensors.

Taxonomical implications of foliar epidermal anatomy of Impatiens L. species (Balsaminaceae) in the Nilgiris, Southern Western Ghats, India

The foliar epidermal anatomy of 22 Impatiens species from the family Balsaminaceae was studied. The study intended to determine whether the micromorphological characteristics of the genus Impatiens were taxonomically significant and would aid in the precise identification of the species. The qualitative and quantitative traits as well as diagnostic characteristics were identified using a Light microscope. Variations were observed in both adaxial and abaxial leaf micromorphological characters like the shape of the epidermal and guard cells, anticlinal wall pattern, lobes per cell, stomatal pore, distribution of stomata, type of stomata and the presence and nature of trichomes. Anomocyic stomata exclusively occurred in all the studied Impatiens species. Stomata were present on both the surface of I. scabriscula B. Heyne ex Walland I. balsamina L., while in rest of the studied species stomata restricted on abaxial surface. An elliptical pore is the dominant type of stomatal pore among the investigated impatiens taxa. Uniseriate multicellular trichomes were observed (I. tenella B.Heyne ex Hook., I. fruticosa Lesch ex DC, I. gardeneriana Wight, I. minor (DC.) Bennet, I. rufescens Benth ex Wight & Arn). For accurate species delineation and identification in the genus Impatiens, taxonomic keys have been developed based on foliar micromorphology.

Investigation of Axial Tensile Fracture Performance of Recycled Brick Coarse Aggregate Concrete Using a Cohesion Model.

Currently, microscopic research on the tensile fracture properties of recycled brick coarse aggregate concrete has mainly adopted microscopy techniques, which can clearly observe the actual damage situations of each phase material but are unable to individually analyze the effect of a specific material factor on the tensile properties of recycled concrete. This brings much uncertainty to the practical application of recycled concrete. Therefore, this study proposes a cohesive zone model (CZM) for simulating the tensile fracture of recycled brick coarse aggregate (RBCA) concrete. To this end, the study explores the effects of various critical factors on the fracture mode and bearing capacity of recycled brick aggregate concrete, including the replacement rate of recycled brick coarse aggregate, pore structure, interfacial transition zone (ITZ) strength, mortar strength, and volume fraction of brick aggregate. The results indicate that, when the minor to major axis ratio of elliptical pores is 0.5 ≤ K < 1, the following order of influence can be observed: random convex polygonal pores, circular pores, and elliptical pores. Moreover, excessively strengthening the ITZ and mortar does not significantly enhance the tensile performance of RBCA concrete. The distribution location of aggregate has a significant impact on the crack shape of recycled concrete, as does the pore structure, due to their randomness. Therefore, this article also discusses these. These findings contribute to a comprehensive understanding of the tensile properties of recycled brick coarse aggregate and provide insights into optimizing its behavior.

Analysis of pore-fracture structure evolution and permeability in tar-rich coal under high-temperature pyrolysis using μCT technology

To study the internal evolution characteristics of tar-rich coal under high-temperature pyrolysis and improve pyrolysis efficiency, three-dimensional reconstruction and analysis of tar-rich coal from northern Shaanxi after high-temperature pyrolysis were conducted using μCT technology. The evolutionary development of pore and fracture structure at different temperatures and the relationship between pore-fractures and permeability was studied and discussed. The results show that when tar-rich coal from 300 to 600 °C, it mainly undergoes two stages: in the first stage, the internal substance structure of the coal mainly undergoes thermal cracking, forming large fracture bands; in the second stage, the coal undergoes intense pyrolysis reactions, resulting in primarily circular or elliptical large pore structures within the coal, with a reduction in the number of fractures. Furthermore, a strong exponential relationship is exhibited between the porosity and permeability of tar-rich coal, and a predictive equation is provided. When the temperature exceeds 500 °C, the coupled effect of pores and fractures contributes more than 20% to permeability, and its impact cannot be ignored.

Design and simulation of a compact plasmonic photonic crystal fiber filter with wide band and high extinction ratio

In order to realize the performance optimization and function expansion of modern all-optical systems, this work presents a compact plasmonic photonic crystal fiber (PCF) filter, using finite element tool. The deposited gold and graphene layers within the elliptical pores interact with the transmitted light, creating surface plasmon resonance (SPR) effect that amplifies the energy difference between x- and y-polarized light greatly. The simulation results indicate that the structural parameters are configured with the cladding holes' diameter of 0.6 μm, the large-holes’ diameter of 1.2 μm, the inner small-holes’ diameter of 0.2 μm, the lattice constant of 2.0 μm, the elliptical holes' minor axis length of 0.45 μm, the elliptical holes' major axis length of 1.30 μm, the gold layer thickness of 50 nm, and the graphene layer thickness of 20 nm, the central wavelength of the proposed PCF filter is 1.56 μm. When the length of this PCF filter is 1 mm, a maximum extinction ratio (ER) of 133 dB, an operating bandwidth exceeding 800 nm, covering two common communication windows of 1.31 μm and 1.55 μm, as well as a low insertion loss (IL) of 0.59 dB can be achieved. What's more, the feasibility of fabricating the device is also examined. This filter with compactness, broadband and high-extinction demonstrates promising applications in optical communication, optical sensing, optical computing, and various other fields.

Correlation between hydrogen absorption capacity and microstructure of Fe-rich Sm-Co-Fe-Cu-Zr permanent magnetic alloys

The correlation between hydrogen absorption capacity (HAC) and the microstructure of Sm26.2CobalFexCu4.0Zr2.3 (x = 23 wt%, 25 wt%, 27 wt%, 30 wt%) ingots and cast strips was systematically investigated. As the temperature rises from 373 to 423 K, the activation time, hydrogen absorption time and HAC of the Sm26.2CobalFe23Cu4.0Zr2.3 ingot decrease by 14.4%, 14.1%, and 19.3%, respectively. Dispersed 1:5 phase provides more channels for hydrogen diffusion, which is the main reason that HAC increases with the x increasing. The HAC of the same compound strips increases as the particles size of the pre-crushed decreases. However, no further embrittlement behavior appears in pre-crushed strips, which reaches an equal HAC as ingots. Micro-computerized tomography reveals that ingots contain small spherical-like holes and large flake micro-cracks, whereas strips mainly contain elliptical pores. The effects of grain size and inner defects size on structure stability were invested by Abaqus. Simulation results reveal that the superior embrittlement behavior of the ingots is predominantly influenced by the presence of large flake-like micro-cracks.

Stochastic microstructure modeling and thermal conductivity of coal-based carbon foam

The mechanical, thermal and electrical properties and applications of coal-based carbon foam (CCF) are based on its porous structure. In the present study, a 3-D stochastic numerical program was used to model the microstructure of CCF considering its non-uniformly distributed elliptical pores (i.e., pore dispersity). The heuristic program derived from the foaming process reflected the heterogeneity of foam. Stochastic seeding was used to regulate the pore location dispersity caused by material unevenness and impurities, while the pore size dispersity was revealed by assigning dissolved gas to adjacent pores during pore growth. The structural similarity was confirmed by comparison between the established model and the actual foam in geometrical features, including ligament edge/wall thickness, pore size and ligament cross-section shape etc. The effective thermal conductivity (ETC) of the stochastic model is more sensitive to changes in porosity, compared to that of uniform model of previous literatures. The reason was suspected to be the longer heat transfer path and less cross-section variation of the ligaments of heterogeneous foam. Pore location and size dispersities were regulated in a stable range by program parameters, which indicated that the stochastic model accurately simulated the microstructural complexity of CCF.

Confinement of a Styryl Dye into Nanoporous Aluminophosphates: Channels vs. Cavities.

Styryl dyes are generally poor fluorescent molecules inherited from their flexible molecular structures. However, their emissive properties can be boosted by restricting their molecular motions. A tight confinement into inorganic molecular sieves is a good strategy to yield highly fluorescent hybrid systems. In this work, we compare the confinement effect of two Mg-aluminophosphate zeotypes with distinct pore systems (the AEL framework, a one-dimensional channeled structure with elliptical pores of 6.5 Å × 4.0 Å, and the CHA framework, composed of large cavities of 6.7 Å × 10.0 Å connected by eight-ring narrower windows) for the encapsulation of 4-DASPI styryl dye (trans-4-[4-(Dimethylamino)styryl]-1-methylpyridinium iodide). The resultant hybrid systems display significantly improved photophysical features compared to 4-DASPI in solution as a result of tight confinement in both host inorganic frameworks. Molecular simulations reveal a tighter confinement of 4-DASPI in the elliptical channels of AEL, explaining its excellent photophysical properties. On the other hand, a singular arrangement of 4-DASPI dye is found when confined within the cavity-based CHA framework, where the 4-DASPI molecule spans along two adjacent cavities, with each aromatic ring sitting on these adjacent cavities and the polymethine chain residing within the narrower eight-ring window. However, despite the singularity of this host-guest arrangement, it provides less tight confinement for 4-DASPI than AEL, resulting in a slightly lower quantum yield.

The effect of inclusions and pores on creep crack propagation of linear friction welded joints of GH4169 superalloy

Superalloy has become the key material in components of blisks for aero-engines produced by linear friction welding. However, during the long-term service of the blisks, stress rupture occurs on the blisk under long-term creep. In this study, the linear friction welded joints of GH4169 superalloy were studied with experiments and numerical simulation. The Sin-Hyperbolic creep-damage constitutive model was established. Based on the compact tension specimen model, the numerical simulation of crack propagation was carried out, analyzing the effect of defects in linear friction welded joints such as cracks, inclusions, and pores on creep crack propagation. Results show that inclusions have an impact on the deflection and promotion of creep crack propagation. The maximum values of crack propagation rate can be observed when radius is 0.03 mm for circular inclusions and length-to-diameter ratio is 3 for elliptical inclusions, respectively. When the transverse distance between the center of the pore and the crack tip is 0.6 mm, the effect on crack propagation is the most significant, with the crack deflecting and expanding towards the direction of the pore. The effect of elliptical pores on creep crack propagation is more significant than that of circular pores. When the length-to-diameter ratio is 3, cracks have initiated firstly on both sides of elliptical pores. When the angle between the pore and the prefabricated crack is 0°, the elliptical pore has the greatest deflection effect on the creep crack. Overall, the effect of pores on creep crack propagation is stronger than that of inclusions.

Controlling product selectivity and catalyst lifetime by altering acid strength, cavity size of SAPO, and diffusion rate of methanol in the MTO reaction: DFT and MD calculations.

The initiation mechanisms of the MTO process over silicoaluminophosphate (SAPO) catalysts with zeolite-like structures using first-principles calculations have been investigated. The supramolecular system of silicoaluminophosphates consisting of inorganic cages with Brønsted acid sites and trapped organic compounds was used as a catalyst in the MTO reaction. To study the structure-property relationship in more detail, the effect of acidity and cage size of different types of SAPOs (SAPO-18, SAPO-34, and SAPO-17 with CHA, AEI, and ERI structures, respectively) in the aromatic cycle of hydrocarbon pool mechanism was investigated. The differences in reaction barriers can be explained by the cage size, pore topology, and environment of framework protons of materials. Product selectivity was controlled by using cavity-type zeolite, the steric constraint of the cavity for the formation of critical intermediates, and acidic strength. The results show that ethylene selectivity increases as the cavity size decreases, and the elliptical pore size of the structures decreases, thereby decreasing the acidity of the zeolite structure, leading to an increase in propylene selectivity. SAPO-18 exhibits the longest reaction lifetime and has the highest amount of carbonaceous material after reaction completion. SAPO-17 with small pore and cavity size is selective to ethylene, although it shows a rapid catalyst deactivation rate.

A GENERALIZED FRACTAL-BASED APPROACH FOR STRESS-DEPENDENT PERMEABILITY OF POROUS ROCKS

The pore geometry of porous rocks is fundamental for accurate description of stress dependence of effective permeability, which is an important parameter of mass transfer in porous rocks. An important physical assumption that porous rocks contain numerous elliptical or spherical pores has been shown to be successfully applied to many aspects of hydromechanical coupling properties of porous rocks. To investigate the detailed description of pore structures on the degree of effect on the coupled hydromechanical process, in this work, a generalized stress-dependent model for permeability of porous rocks has been proposed based on fractal geometry theory and mechanics of porous rock. The proposed model is expressed as a nonlinear function of pore structure parameters, such as aspect ratio ([Formula: see text]), the fractal dimensions ([Formula: see text] and [Formula: see text]) for tortuosity, the initial fractal dimension ([Formula: see text]), and initial porosity ([Formula: see text]) as well as matrix elastic constants ([Formula: see text] and [Formula: see text]) of porous rocks without any empirical parameter. The validity of the proposed models is verified by the good agreements between available experimental data and theoretical predictions of stress-dependent permeabilities of porous rocks. Detailed discussions of the essential effects of pore structures parameters and material elastic constants of porous rocks on the dimensionless stress-dependent permeabilities are performed. It is found that the stress parameters ([Formula: see text] and [Formula: see text]) have remarkable effects on the dimensionless stress-dependent permeabilities compared with other parameters ([Formula: see text] and [Formula: see text]). The proposed model may contribute to a better quantitative understanding of the coupled hydromechanical properties of porous rocks.

Effect of biochar and hydrochar of pistachio residues on physical quality indicators of a sandy loam soil

The carbonization of agricultural residues into carbon-rich biochars can be considered as one of the practical methods in sustainable management. The objectives of this study were to: (i) investigate and compare the chemical, physical and micromorphological properties of biochar and hydrochar produced from pistachio (Pistacia vera) residues, and (ii) compare the effects of these chars on the physical quality of a sandy loam soil (classified as Typic Haplocalcids) in pistachio orchards. The physical and chemical characteristics of the biochar and hydrochar were determined. Scanning electron microscopy images showed that hydrochar had a spherical pore structure while the biochar had elliptical pores. The chars were different in terms of functional groups, ratio of elemental composition, and electrical conductivity. Both chars were added at the rates of 0, 1 and 2%w/w to the soil and incubated for nine months under wet and dry cycles. Then, soil physical indicators including bulk density (ρb), dry and wet aggregate stability, water retention curve, saturated water content (θs), field capacity (θFC) and plant available water (PAW) were determined. The results showed that the hydrochar and biochar application had no significant effect on the ρb and dry aggregate stability. However, the percentage of water-stable aggregates larger than 0.25 mm increased at the rate of 1%w/w of chars in comparison with the control. The θs, θFC and PAW increased at both rates of chars when compared with the control. The residual water content (θr) increased at the rate of 1%w/w of chars compared to the untreated soil. It can be concluded that chars of pistachio residues can affect soil physical quality indicators and pore size distribution by the means of different mechanisms like the effect of morphological characteristics of chars, forming complexes between the soil particles, and creating hydrophobic coatings on the soil particles and aggregates.

Harnessing local flow in buckling pores for low-frequency attenuation

While attenuation at low frequencies remains highly desirable for industrial applications such as multistory buildings or spacecraft propellant tanks, fluid-filled rocks can achieve this goal naturally by so-called local flow in their heterogeneous pore structure. The present work aims at combining this natural phenomenon with controlled instabilities in light-weight structures. Buckling of their pores is harnessed to break local geometric symmetry and maximize the local-flow effect. A prototype structure with elliptical pores is analyzed numerically. It does not show local flow or attenuation for the starting geometry, but reversibly switches into an attenuating structure by imposing a critical buckling strain. The simulations reach inverse quality factors larger than 0.3 around 5Hz for material properties of air-filled silicone rubber. A key to high attenuation is a tradeoff between the unstable structure and the pore fluid. If the solid is too soft, the fluid-filled pores are not compressed and buckling is not triggered. If the solid is too stiff, most energy is stored elastically and not dissipated by fluid flow. The proposed, fluid-filled structure allows for a scalable, light-weight material exhibiting significant low-frequency attenuation.

A new multi-scale pore transport capacity model considering elliptical shape and retention effect of unequal-thickness water films

Most of current permeability evaluation models for shale gas reservoirs ignore the influence of imbibition during fracturing, moreover, several of the considerations are different from real conditions, for example, shale pore shape is circular and water film is with equal thickness, which is convenient for calculation but adverse to evaluation accuracy. In the study, shale pore shapes are closer to ellipse by statistically analyzing the scanning electron microscopy results, the thickness of water film is not equal on elliptical pore surface but related to the curvature. Based on these new insights, a quantitative model for determining the unequal thickness of water film was established, and then a new multi-scale elliptical pore permeability model, considering non-equal-thickness water film, wall roughness, stress sensibility, and retention effect, was established based on the multi-scale flow weighting theory. The prediction results of this permeability model are similar to the test results, and are more accurate than that of the previous models. Finally, factors analysis showed that the effect of roughness on permeability was small, but the negative impact of water film and stress sensitivity on permeability was significant.

Antiviral/antibacterial and mechanical properties of HAp/TiO2 porous composite

This study aims at observing damage behavior of porous components under compression using multi modal measurement combining Acoustic Emission (AE) and IR.uniform porous structures were fabricated using a 3D printer in order to observe the damage process during the compressive loading. Then, the influence of the crack-connecting behavior among pores on mechanical properties was investigated experimentally. By using AE and IR method, high agreement between the onset of AE signal and temperature change at the surface of the porous material was revealed. The crack initiation location of porous materials with spherical and elliptical pores is found to be near the estimated location of the sudden AE emission source.

Cumulative deformation prediction and microstructure change of coarse-grained soil under cyclic loading

This research aims to reveal the macroscopic cumulative deformation development pattern and internal structural change characteristics of coarse-grained soils under moving vehicle loads. Dynamic triaxial tests are used to investigate the development of cumulative deformation of coarse-grained soils under various deviatoric stresses, moisture contents, and loading frequencies. Based on the results of indoor tests, a comprehensive prediction model for the cumulative deformation of coarse-grained soils was established. The cumulative deformation increases with the increasing deviatoric stress, moisture content, and loading frequency. As the deviatoric stress grows, the cumulative deformation rate increases correspondingly. The cumulative deformation prediction model for coarse-grained soils proposed in this study has high accuracy. Cyclic loading reduces the number of large pores, increases the number of smaller pores, and increases the proportion of micropores with increasing deviatoric stress and moisture content. The effect of loading frequency on the deformation of coarse-grained soils is relatively small but still not negligible. Cyclic dynamic loading can transform the long pores in coarse-grained soil subgrade filler into elliptical and circular pores. The increase in moisture content can increase the proportion of long pores in coarse-grained soil filler. This research can deliver a valuable reference for analyzing the cumulative deformation of coarse-grained soils subjected to cyclic loading.

Enhanced pollutant photodegradation over nanoporous titanium-vanadium oxides with improved interfacial interactions

This study addressed the separation problem of colloidal catalytic powder from its solution and pore blockage of traditional metallic oxides by fabricating nanoporous composites of titanium (Ti)-vanadium (V) oxide via magnetron sputtering, electrochemical anodization, and annealing processes. The effect of V-deposited loading on the composite semiconductors was investigated by varying V sputtering power (20–250 W) to correlate their physicochemical properties to the photodegradation performance of methylene blue. The obtained semiconductors revealed circular and elliptical pores (14–23 nm) and formed different metallic and metallic oxide crystalline phases. Within the nanoporous composite layer, V ions substituted Ti4+, leading to Ti3+ formation accompanied by decreased band gap values and higher visible-light absorption. Thus, the band gap of TiO2 was 3.15 eV, while that of Ti-V oxide with the maximum V content (at 250 W) was 2.47 eV. The interfacial separators between clusters in the mentioned composite created traps disrupting the charge carrier movements between crystallites, thereby decreasing the photoactivity. In contrast, the composite prepared with the minimum V content showed approximately 90% degradation efficiency under solar-simulated irradiation resulting from the homogeneous V dispersion and the lower recombination possibility, owing to its p-n heterojunction constituent. The nanoporous photocatalyst layers with their novel synthesis approach and outstanding performance can be applied in other environmental remediation applications.

Pure Silica with Ordered Silanols for Propylene/Propane Adsorptive Separation Unraveled by Three-Dimensional Electron Diffraction.

Adsorptive separation of propylene (C3H6) from propane (C3H8), which could deal with energy-intensive cryogenic distillation technologies, remains challenging due to their similar physiochemical properties. Herein, we present a pure silica zeolite with ordered silanols (OSs), whose crystallographic structure was unraveled by the advanced three-dimensional electron diffraction (3D ED), displaying the highly efficient separation of propylene from propane under ambient conditions. The 3D ED technique enables us to investigate its 8-ring pore opening transformation from the round one to the elliptical one during the removal of organic structure-directing agents. Such unique elliptical 8-ring pore openings can exclude larger-size propane and only adsorb propylene. Its C3H6/C3H8 separation performance is also confirmed by column breakthrough experiments, showing a high dynamic adsorption capacity of 53.36 cm3 g-1 for C3H6 but negligible C3H8 under ambient conditions. The dynamic capacity for C3H6 is superior to that of the well-known pure silica DDR-type zeolite (31.07 cm3 g-1). The density functional theory calculation demonstrates that the adsorbed propylene is distributed in the heart-shaped cavity and has a weak interaction with the OSs.

Variations in the Indonesian Sauromatum horsfieldii Miq. (Araceae) Based on Characteristics of Morphology, Anatomy and Cytology

Sauromatum horfieldii Miq. (Araceae) is distributed from India, China to South East Asia. In Indonesia, the species only occurs in Sumatera, Jawa, and Bali. This study investigated the morphological, anatomical, and cytological diversity of three populations of the species, one from each of these Indonesian islands. The results showed that there was variation in morphology of the petiole, number of leaflets and leaf margin. The stomatal complex consisted of elliptical pores with reniform guard cells and two or three subsidiary cells. The Indonesian plants of S. horsfieldii possessed two stomatal types, namely anomocytic and anisocytic, both with abaxial distribution (hypostomatic). Measurements on each population showed average stomatal indices (SI) of 10.01, 10.02 and 14.55, average stomatal lengths of 34.6, 33.8 and 29.50 μm, and average stomatal widths of 20.8, 21.1 and 16.50 μm for Sumatera, Jawa, and Bali, respectively. The epidermal cells are mostly irregular and somewhat undulate. The chromosome number for all the accessions was 2n = 26.