Pore Expansion Research Articles

Effect of Ultrasound Pretreatment on the Moisture Migration and Quality of Cantharellus cibarius Following Hot Air Drying.

The effect of different ultrasound pretreatment powers (0-500 W) before hot air drying on the moisture migration and quality of Cantharellus cibarius (C. cibarius) was investigated in this study. The results showed that the ultrasound pretreatment accelerated the drying rate. When the ultrasound power was 400 W, the drying time of C. cibarius was reduced by 18.90% compared with the control group. The low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) results showed that the ultrasound pretreatment increased the water mobility in C. cibarius. The scanning electron microscopy (SEM) results revealed that the ultrasound pretreatment promoted the expansion of intercellular pores. In addition, the rehydration capacity and quality characteristics of the ultrasound-pretreated dried C. cibarius were better than those of the control group. Overall, this study concluded that ultrasound pretreatment is a promising pretreatment method for the hot air drying of C. cibarius products to reduce the total drying time significantly and improve the retention rate of the total phenolics and flavonoids of dried C. cibarius.

Ultrasound-assisted extraction of cranberry seed oil: food waste valorization approach

Cranberry pomace considered as a by-product of fruit industry contains seeds which may be processed to highly nutritive oil. Conventional extraction methods may be, however, harmful to natural environment, thus alternative, ultrasound-assisted extraction method may be useful tool to reduce environmental impact. In the following study, sonication was applied to extract oil from cranberry seeds. The aim of the study was to determine the most efficient conditions of ultrasound-assisted extraction of oil and to investigate sonication influence on the properties of final product. Ultrasound amplitude and extraction time were independent variables; yield and maximum induction time of oils were responses. The most efficient conditions were amplitude of 95% and extraction time of 11.38 min. Model predicted extraction yield of 22.55 ± 0.36% (vs. actual 21.98 ± 0.08%) and induction time of 52.60 ± 0.95 min (vs. actual 61.95 ± 3.06 min). Detailed analyses of oil extracted in the most efficient conditions and the control sample were performed. Kinetic parameters of oil oxidation, fatty acid profile and distribution, melting characteristics studies were carried out. Sonication influenced activation energy of oxidation reaction, contribution of chosen fatty acids (oleic, α-linolenic and eicosenoic fatty acids) and distribution of oleic and α-linolenic fatty acids in sn-2 position of triacylglycerols. Slight changes in melting profile of oils were also recorded. Scanning electron microscopy of cranberry seeds revealed that ultrasound treatment resulted in pore enlargement and fat agglomeration damage. Additional studies of thermal properties of cranberry seeds: differential scanning calorimetry and modulated differential scanning calorimetry were performed, which confirmed that cranberry seeds may be a new source of oil with unique properties.

High-performance flexible pressure sensor based on ordered double-level nanopillar array films: Design, development, and modeling

To improve the sensitivity and broaden the range of flexible pressure sensors, we proposed a high-performance flexible pressure sensor based on ordered double-level nanopillar array films. In this work, polypyrrole/multi-walled carbon nanotube/polyurethane (PPy/MWCNT/PU) conductive films with double-level nanopillar array microstructures were prepared by continuously adjusting the oxidation and pore expansion parameters of a porous anodic alumina template (AAO), where the high pillar height was 1243.0 ± 7.0 nm, and the low pillar height was 868.0 ± 4.70 nm. We studied the influence of the structural characteristics of ordered double-level nanopillar array conductive films and a flexible pressure sensor on the sensing performance using finite element simulations, the establishment of sensing mechanism, and sensor performance measurements. The results showed that the pressure was positively correlated with the change rate of strain and the surface microstructure contact area of the ordered double-level nanopillar array films. The sensor sensitivity reached 208.353 kPa−1, and its range was extended by 267%. In addition, the sensor, which could monitor vocalization, drinking pulse and finger movements, could be used in a wide range of applications, including wearable medical monitoring and smart sign language textiles.

Multi-scale multivariate detection method for the effective impact range of hydraulic fracturing in coal seam

Hydraulic fracturing enhances coal seam permeability and reduces original gas content. Determining the effective range of hydraulic fracturing is essential in evaluating its effectiveness. This paper analyzes physical field changes during hydraulic fracturing and proposes a multi-scale multivariate detection method for determining the effective range of hydraulic fracturing in coal seams based on changes in wave velocity and resistivity due to fracture expansion.The method was validated through field experiments. The result shows that vibration wave computed tomography (VWCT) is a passive, large-scale area detection method. In contrast, the direct current (DC) method is a small-scale, local active detection method. In the hydraulic fracturing process, the microseismic (MS) events increase. After fracturing, the wave velocity of coal seam decreases significantly, indicating the formation of fractures around the fractured holes and a fracture zone. The fracturing expands the pre-existing fractures adjacent to fractured holes, forming a fracture network between them and natural fractures, leading to a decrease in wave velocity around the coal seam. The DC detection results indicate a noticeable development of pores around the fractured holes following hydraulic fracturing. The increased resistance value area is mainly concentrated on both sides of the 9–4 drilling, with an influence range of approximately 30 m, and an increased range of 100–400 Ω·m, indicating a hydraulic fracturing pore expansion range of 30 m in coal seams. Comprehensively, the maximum impact area of fracturing is the area surrounding the fractured holes, and the impact area is not uniform. The DC method test results reflect the extension of fracturing around fractured holes, while the VWCT test results represent the extension of fracturing around fractured holes and the connectivity of primary fractures, both of which include each other.

Skin pore imaging using spectral-domain optical coherence tomography: a case report.

Sebum is an important component of the skin that has attracted attention in many fields, including dermatology and cosmetics. Pore expansion due to sebum on the skin can lead to various problems. Therefore, it is necessary to analyze the morphological characteristics of sebum. In this study, we used optical coherence tomography (OCT) to evaluate facial sebum areas. We obtained the OCT maximum amplitude projection (MAP) image and a cross-sectional image of skin pores in the facial area. Subsequently, we detected the sebum in skin pores using the detection algorithm of the ImageJ software to quantitatively determine the size of randomly selected pores in the proposed MAP images. Additionally, the pore size was analyzed by acquiring images before and after facial sebum extraction. According to our research, facial sebum can be morphologically described using the OCT system. Since OCT imaging enables specific analysis of skin parameters, including pores and sebum, skin analysis employing OCT could be an effective method for further research.

Performance of screw piles in thick collapsible loess

The bearing capacity of the composite foundation would be significantly increased by the squeezing effect of soil displacement screw pile. To investigate the effect of soil displacement screw pile treatment on the large-thickness collapsible loess foundation, full-scale field tests and pore expansion theory were used to compare the physical and mechanical properties of the soil around the pile before and after soil displacement screw pile treatment. It was found that the maximum influence range of a single pile in loess foundation was 3D, and the effective influence range was 2.5D. Compared with natural foundation, the average dry density of soil between two and three piles increased by 23 % and 15 %, and the compression coefficient decreased by 57 % and 38 %, respectively, when the pile spacing was 2.0D and 2.5D. The collapsibility coefficient and self-weight collapsibility of soil between two and three piles were far less than 0.015 when the pile spacing was less than or equal to 2.5D. The soil deformation caused by compaction was mainly plastic deformation. The plastic zone radius calculated by pore expansion theory can be used to estimate the compaction range of soil displacement screw piles in large-thickness loess regions. When the pile spacing was 2D and 2.5D, compared with the natural foundation, the characteristic values of soil bearing capacity between piles increased by 60 % and 30 %, that soil displacement screw pile of plain soil composite foundation increased by 220 % and 200 %, and that of plain concrete soil displacement screw pile increases by 450 % and 400 %, respectively. It shows that a soil displacement screw pile can significantly increase the bearing capacity of a large-thickness collapsible loess foundation. When the area replacement rate was 0.145–0.23, the pile-soil stress ratio of soil displacement screw piles in large-thickness collapsible loess region ranged from 2.6 to 4.7.

Experimental study on the evolution of rock microstructure under dynamic water pressure

The pore structure of rocks has an important influence on their mechanical strength and permeability. In this experiment, the evolution of the internal multiscale structure of rocks under the action of seepage flow is investigated. The results show that progressive damage occurs inside the rock at the early stage of osmotic pressure action, and the expansion and connectivity of pores form a damage mutation at a certain moment, which triggers rock damage destabilization. In addition, a damage evolution equation based on NMR test values is established to obtain the threshold of damage mutation in rocks; It is also found that rock permeability is mainly affected by pore connectivity, and the effect of porosity on rock permeability is relatively small.

Fabrication of hydrophilic porous carbon from polyvinylidene chloride-resin via synergetic activation of ZnO and tetrahydrofuran for aqueous supercapacitors

For high capacitance, aqueous supercapacitors use large-area porous carbon electrode based on the charging principle of ion adsorption. Nonpolar hydrophobic carbon prevents ion adsorption, limiting the exploitation of porous surfaces. A carbon synthesis method was developed from pyrolysis of a polyvinylidene chloride-resin precursor and excess ZnO to derive a highly porous structure with a high surface area. Ion adsorption is limited by the small, newly formed pores. Added tetrahydrofuran expands the reaction region between the precursor and etchant during pyrolysis by dissolving the precursor. Moreover, tetrahydrofuran activates oxygen in the precursor and ZnO during pyrolysis, forming hydrophilic phenol and carboxylic acid. The hydrophilicity and pore expansion induced during pyrolysis convert the extra surface area into active charging sites. Hydrophilic carbon with enlarged pores increases the specific capacitance by 5.7 times to 126 F g−1 (at 5 mV s−1) and the rate capability by 2.7 times to 62% (50 mV s−1 vs. 5 mV s−1) in neutral K2SO4 solution compared to carbon made from polyvinylidene chloride-resin. Notably, the synthesized functional groups yielded a high capacitance of 243 F g−1 based on the faradaic charging in the KOH electrolyte. Hydrophilic carbon originating from polyvinylidene chloride-resin can be a potential electrode with a high capacitance for aqueous supercapacitors.

Generation of Site-Selective Structural Vacancies in a Multinary Metal-Organic Framework for Enhanced Catalysis.

Generating structural vacancies in metal-organic frameworks (MOFs) by partially removing the inorganic and organic units from the scaffolds is an effective strategy to modulate the pore parameters of the extended structures. However, pore enlargement is accomplished at the cost of loss in the number of active sites in typical MOFs, since dissociations of coordination linkages to create vacancies are not site-selective. Here, we performed site-specific vacancy generation in a multinary MOF (FDM-6) by selectively hydrolyzing the weak Zn─carboxylate linkages and keeping the strong Cu─pyrazolate linkages untouched. Surface area and pore size range of the materials could be systematically tuned by adjusting the water content and hydrolysis time. More than 56% of the Zn(II) sites in FDM-6 could be vacant, as evidenced by the atom occupancy analysis using powder X-ray diffraction, while most of the redox-active Cu sites are held in the backbone. The vacancies create highly connected mesopores, thus guaranteeing facile transportation of the guest molecules toward the active sites. Compared with the pristine MOF, FDM-6 with site-selective vacancies shows enhanced catalytic activity in bulky aromatic alcohol oxidation. Overall, the multinary MOF provides a platform in which both pore size enhancement and full retainment of active sites could be delivered in one framework by simple vacancy engineering.

Migration of inert materials during coking of molded coal

Since the maldistribution of substances with poor melting and expansion properties decreases the strength of coke, we investigated whether these substances gather or disperse during coking process. Coal briquettes (before coking) and cokes (after coking) containing a predetermined amount of alumina beads were prepared. These beads constituted 2–15 vol% of the samples. A three-dimensional analytical object was constructed by X-ray CT images of coal briquette or coke with alumina beads, and isolated alumina beads were extracted from analytical objects by image processing. The number of isolated alumina beads increased after coking in any mixing ratios. Therefore, it was shown that the alumina beads dispersed each other during coking. The observed result could be attributed to the expansion of pores near the contact points between agglomerated alumina beads, resulting in the expulsion of the beads. At the lower part of the sample, where the effect of expansion was small, the same ash before and after carbonization can be found. Focusing on the area near the ash, alumina beads with the same distance from the same ash are observed before and after the coking. This indicates that there are alumina beads that have not moved during coking. The reason why the alumina beads did not move may be using low fluidity coal and high-density coal briquette as the raw material of coke. This suggests that the high-density coal briquette may prevent the coke strength from decreasing due to the suppression of insoluble matter agglomeration.

Experimental study on high temperatures performance of rubberized geopolymer mortar

Nowadays, fire accidents occur frequently, and both buildings and structures or traffic roads are threatened by fire to varying degrees, and the mortar structure is often in direct contact with fire. Therefore, it is necessary to study the performance of mortar under high temperature. Geopolymer is a new type of green environmental protection building material with good high temperature resistance. Waste rubber will soften and decompose under high temperature, and the holes formed can release the steam pressure inside the structure, which is helpful to ease the internal cracking of the structure. At present, it has been proved that waste rubber has a beneficial effect on the resistance of mortar to high temperature. The research of waste rubber in Portland cement mortar has made relevant achievements, but the research on the combination of geopolymer rubber is relatively small. Therefore, in view of this lack, this study supplements the material properties of geopolymer mortar under four rubber particle sizes (4, 1.7, 0.83, and 0.27 mm) and five temperatures (25, 200, 400, 600 and 800 °C), namely, surface observations, mass loss, compressive and flexural strengths, ultrasonic pulse velocity (UPV) and microstructure change. The results show that the addition of rubber particles will increase the mass loss of rubberized geopolymer mortar (RGM), but the advantage is that it can reduce the burst risk. The addition of fine particle rubber can improve the ability of RGM to resist cracking and deformation at higher temperatures. The results shows that the UPV can reflect the mass and intensity change of RGM laterally. The microscopic results shows that the main reason for the lower strength is the expansion of microcracks and pores in RGM matrix at high temperature.

Experimental study on the effects of pre-oxidation on the pore structure and fractal characteristics of coal

ABSTRACT To assess the effects of pre-oxidation on pore structures and fractal features of coal samples, pre-oxidized coals at various oxidation temperatures were prepared and compared. Pore structure parameters of coal samples were analyzed qualitatively and quantitatively using electron scanning microscopy (SEM) and N2 adsorption. The pore volume of coal samples increased first and then decreased with the increase of oxidation temperature. Among them, the pre-oxidized coal at 150°C is the highest, which is 27.92% higher than the raw coal. The fractal features of coal samples were calculated by fractal theory. It was found that pre-oxidation makes pore fissures of coal samples develop with obvious pore expansion effect, which is more obvious at the higher pre-oxidation temperature. In addition, fractal dimension D 2 of coal samples was increased by pre-oxidation, indicating that pore structures of pre-oxidized coal are more complex than those of raw coal.

Fracture behavior of a high pressure die casting AlSi10MnMg alloy with varied porosity levels

The fracture behavior of a high pressure die casting AlSi10MnMg alloy with varied porosity levels is investigated by synchrotron radiation X-ray computed tomography. Attention is focused on origin of crack and the evolution of porosity in the process of plastic deformation. Different from in-situ 3D tensile test, load-off specimen after plastic deformation is applied for this experiment and it is closer to the real scene. Results show that multiple defects are proposed in high pressure die casting AlSi10MnMg alloy including shrinkage, gas pore, externally solidified primary iron-rich phase (ESC-IMCI) and heterogeneous layers. In a lower-porosity sample, the surface defects like skin layer are a main crack source and a radial river pattern exhibits in crack surface. No new pores generated in the process of plastic deformation. In a higher-porosity sample, no obvious crack source and radial crack propagation path can be identified while the large crack surface fluctuation and tortuous morphology are obtained. The collapse of pre-existing small-sized pores exert a vital role in connecting large-scale pores. The micro-crack initiation and propagation originate from the expansion, consolidation and collapse of pores, especially the irregular pores.

Impedance Factor of Hydraulic Conductivity for Frozen Soil Based on Ice Segregation Theory and Its Application

AbstractThe necessity and rationality of using an impedance factor in the calculation of hydraulic conductivity of frozen soil has been an ongoing debate. To address this issue, ice segregation theory was used to analyze the physical meaning of the impedance factor. Based on assumptions sourced from segregation theory, experimental evidence regarding the hydraulic conductivity of frozen soil and the Gibbs‐Thompson effect, a relationship between the impedance factor and soil parameters was deduced. The necessity of the impedance factor was discussed under closed unsaturated and open saturated freezing systems. Finally, the derived impedance factor was compared with the current empirical impedance factor. The results showed the following: (a) The impact of the impedance factor on closed unsaturated freezing systems was small. However, an impedance factor was necessary for water migration in freezing systems with a high degree of ice segregation, such as open saturated freezing systems. (b) The derived impedance factor combined with the VG model had good performance for simulating water migration under different freezing conditions. (c) Compared with the empirical impedance factors, the derived impedance factors considered the effect of segregation acceleration caused by the pore expansion, improving the simulation accuracy of water migration at the freezing front. The parameters used to derive the impedance factor were only the initial porosity and the accumulative curve of the particle size grading, which was easily applied and combined with a VG model as a general method for computing the hydraulic conductivity of frozen soil.

Flux enhancement of cellulose nitrate membrane through plasma assisted route for waste and mud water treatment

AbstractFouling of polymeric membranes is a common problem due to its hydrophobic nature. Plasma assisted surface modification of polymeric membranes are immensely popular method in particular for the improvement of antifouling and adhesive properties. The effect of low‐pressure nitrogen plasma on surface morphology, hydrophilicity, structure, permeate flux and ageing effect for the cellulose nitrate polymer membrane are studied in the present work. The cylindrical Langmuir probe and optical emission spectroscopy are used to characterize the plasma. The macro void creation and pore enlargement effects have been observed from scanning electron microscopy images due to the surface etching of the membrane after plasma treatment. The atomic force microscopy analysis shows a prominent enhancement of the surface roughness of the plasma treated membrane. Wettability of membrane is studied as a function of plasma treatment time for treated and untreated membrane. From the contact angle measurement, it is found that the hydrophilicity of the plasma treated membranes increases with plasma treatment time. From gravity filtration process, the enhancement of permeate flux for both waste water and mud water are observed after plasma treatment. The ageing mechanism of the treated membranes is investigated for 30 days for different plasma treatment time. The hydrophobic recovery of plasma treated membranes is significant for initial ageing period of 7 days, after that it has shown almost stable in nature. A theoretical model is developed to study the hydrophilic recovery of plasma treated membranes. It is observed that the experimental results show a very good agreement with the theoretical results.

Discriminatory Gate-Opening Effect in a Flexible Metal-Organic Framework for Inverse CO2 /C2 H2 Separation.

Considering the significant application of acetylene (C2 H2 ) in the manufacturing and petrochemical industries, the selective capture of impurity carbon dioxide (CO2 ) is a crucial task and an enduring challenge. Here, a flexible metal-organic framework (Zn-DPNA) accompanied by a conformation change of the Me2 NH2 + ions in the framework is reported. The solvate-free framework provides a stepped adsorption isotherm and large hysteresis for C2 H2 , but type-I adsorption for CO2 . Owing to their uptakes difference before gate-opening pressure, Zn-DPNA demonstrated favorable inverse CO2 /C2 H2 separation. According to molecular simulation, the higher adsorption enthalpy of CO2 (43.1kJmol-1 ) is due to strong electrostatic interactions with Me2 NH2 + ions, which lock the hydrogen-bond network and narrow pores. Furthermore, the density contours and electrostatic potential verifies the middle of the cage in the large pore favors C2 H2 and repels CO2 , leading to the expansion of the narrow pore and further diffusion of C2 H2 . These results provide a new strategy that optimizes the desired dynamic behavior for one-step purification of C2 H2 .

Fine-tuning mesoporous silica properties by a dual-template ratio as TiO2 support for dye photodegradation booster

Titanium dioxide (TiO2) has been integrated into the surface of mesoporous silica (SMG) synthesized via the hydrothermal approach and a dual template CTAB-Gelatin. XRD, nitrogen adsorption, FTIR, SEM-EDX, and UV–Vis DR spectroscopy were performed to evaluate a 1 wt% TiO2/SMG material. After titania incorporation, the addition of gelatin during the synthesis of SMG increases the pore volume to 0.76 cc/g. The expansion of the silica pores is caused by the development of TiO2 crystal grains on the mesoporous silica-gelatin. An increase in the gelatin-CTAB to mesoporous silica weight ratio modifies the surface area, pore size, and particle size without compromising the meso-structure. In this research, the TiO2/SMG composite demonstrated much greater photodegradability for methylene blue (MB) than the TiO2/mesoporous silica sample without gelatin. The experimental results indicate that the photocatalytic activity of methylene blue from SMG titania/silica samples is reliant on the adsorption ability of the composite and the photocatalytic activity of titania, with optimal activity from samples with the highest surface area and pore volume, which directly increase the Ti: Si ratio and decrease the photodegradability of the composite when the ratio is too high or too low.

Eliminating lattice defects in metal-organic framework molecular-sieving membranes.

Metal-organic framework (MOF) membranes are energy-efficient candidates for molecular separations, but it remains a considerable challenge to eliminate defects at the atomic scale. The enlargement of pores due to defects reduces the molecular-sieving performance in separations and hampers the wider application of MOF membranes, especially for liquid separations, owing to insufficient stability. Here we report the elimination of lattice defects in MOF membranes based on a high-probability theoretical coordination strategy that creates sufficient chemical potential to overcome the steric hindrance that occurs when completely connecting ligands to metal clusters. Lattice defect elimination is observed by real-space high-resolution transmission electron microscopy and studied with a mathematical model and density functional theory calculations. This leads to a family of high-connectivity MOF membranes that possess ångström-sized lattice apertures that realize high and stable separation performance for gases, water desalination and an organic solvent azeotrope. Our strategy could enable a platform for the regulation of nanoconfined molecular transport in MOF pores.

Studying the roles of salt ions in the pore initiation and closure stages in the biomembrane electroporation.

Electroporation shows great potential in biology and biomedical applications. However, there is still a lack of reliable protocol for cell electroporation to achieve a high perforation efficiency due to the unclear influence mechanism of various factors, especially the salt ions in buffer solution. The tiny membrane structure of a cell and the electroporation scale make it difficult to monitor the electroporation process. In this study, we used both molecular dynamics (MD) simulation and experimental methods to explore the influence of salt ions on the electroporation process. Giant unilamellar vesicles (GUVs) were constructed as the model, and sodium chloride (NaCl) was selected as the representative salt ion in this study. The results show that the electroporation process follows lag-burst kinetics, where the lag period first appears after applying the electric field, followed by a rapid pore expansion. For the first time, we find that the salt ion plays opposite roles in different stages of the electroporation process. The accumulation of salt ions near the membrane surface provides an extra potential to promote the pore initiation, while the charge screening effect of the ions within the pore increases the line tension of the pore to induce the instability of the pore and lead to the closure. The GUV electroporation experiments obtain qualitatively consistent results with MD simulations. This work can provide guidance for the selection of parameters for cell electroporation process.

Treatment Protocol on Using Microfocused Ultrasound with Visualization for Skin Quality Improvement: The Korean Experience.

Facial skin quality profoundly influences an individual's perceived appearance and is an important aspect of facial rejuvenation. Facial pore enlargement is one of the most common concerns among Asian individuals that adversely impacts perceived skin surface evenness and affects overall skin quality. One of the major causes of enlarged pores is facial skin laxity. Microfocused ultrasound with visualization (MFU-V; Ultherapy; Merz North America, Inc., Raleigh, N.C.) is indicated for lifting and tightening of the face and neck, and improving the appearance of wrinkles on the décolletage. In addition, it is useful for addressing several aspects of facial rejuvenation, including facial pores, skin laxity, skin unevenness, etc., but there is limited literature on these applications. Thus, we present our proposed MFU-V treatment protocol for achieving a harmonious outcome for attractive skin, along with practical strategies for its application, illustrated in patients presenting with enlarged pores as their main concern. Drawing on our collective experience in using MFU-V for facial rejuvenation and the recently published skin quality framework that advocates addressing interrelated attributes of skin quality for optimal outcomes, we developed a treatment protocol for improving skin quality using MFU-V. This MFU-V treatment protocol reliably improves overall skin quality in patients presenting with enlarged pores, through MFU-V's effects on skin lifting and tightening, and consequent improvement in facial pores and skin texture. This treatment protocol can be readily used as part of a multimodal layering approach to yield successful outcomes in patients with various facial skin concerns.