Connected Pore Structure Research Articles

Quantitative analysis of pore-size influence on granite residual soil permeability using CT scanning

In the field of soil hydrology, pore structure is a key factor affecting soil permeability. This paper uses micro-CT scanning technology to visualize and quantitatively analyze the impact of different pore sizes on the permeability of granite residual soil through scanning, image processing, pore removal, and permeability simulation. The results show that granite residual soil samples have a well-developed connected pore structure, with connected pore diameters ranging from 25-400 μm, while isolated pores are mostly smaller than 50 μm. Medium-sized pores bridge small and large pores, forming an important component of pore connectivity. Pore size significantly affects permeability; the removal of medium-sized pores greatly reduces the connectivity, fractal dimension, and permeability of the remaining pores, indicating that pores in the 100–300 μm range contribute the most to permeability. In contrast, pores smaller than 50 μm and larger than 300 μm have a minimal impact on overall permeability. Effective porosity and fractal dimension are crucial parameters affecting permeability, with a significant linear correlation between the two. This study supply crucial data that delineates the relationship between the structure of soil pores and their permeability, which is invaluable for developing improvement strategies aimed at reducing soil permeability.

Influence of pore structures on friction and wear properties of iron-based oil-containing composites under dry and self-lubricated sliding conditions

This study successfully prepares iron-based oil-containing materials with connected porous structures using TiH2 and nylon 66 short fibers as pore-forming agents. The dehydrogenation of TiH2 can produce large pore cavities and the nylon 66 short fiber with a highly regular shape has a unique advantage in pore channel production. Compared to the iron-based specimen without the pore-forming agent, the oil content of the iron-based specimen with the two pore-forming agents increases by 33.86 %. The tribologica23ee3l properties of the iron-based oil-containing materials under dry and self-lubricated sliding conditions are evaluated using the MM-200 ring-block sliding tribometer and the HDM-20 end-face friction and wear tester, respectively. Special emphasis is given to the effect of pore structures on wear patterns. The results showed that the material's surface is subjected to significant shear failure under dry sliding conditions, leading to the closure of pores due to plastic deformation during the initial sliding. The connected pore structure is a non-dense region, allowing shear damage to occur in the deeper subsurface of the matrix and increasing the material's wear rate. Under self-lubricated conditions, the connected pore structure facilitates the rapid release of lubricating oil, improves the initial lubrication state, and delays pore closure. As compared with dry friction, the wear rate can be reduced by two orders of magnitude under self-lubricating conditions. At a sliding speed of 0.46 m/s, an appropriate load (about 900 N) can enhance the material's ability to continuously and rapidly supply oil.

Preparation of barium alumino-silicate based ceramsite from bauxite, coal gangue and barite: Physical properties, microstructure, and γ-ray shielding behavior

Improving the strength of radiation shielding concrete and the safety of corresponding structures is crucial. However, radiation shielding ultra-high performance concrete (RS-UHPC) often faces the issues of high volume shrinkage and easy cracking. Using barium alumino-silicate-based ceramic as aggregate in concrete is a promising solution for its internal curing effect and excellent radiopacity. In this study, a barium alumino-silicate-based ceramsite (BASC) was developed using bauxite, coal gangue, and barite. The effects of boric anhydride (2 %, 5 %, 8 %), barite powder dosages (20 %, 40 %, 60 %, 80 %), and sintering temperature (1260°C, 1280°C, 1300°C, 1320°C) on the apparent density, compressive strength, and water absorption of the ceramsite were investigated. The microstructure and reaction mechanism of the BASC were analyzed using TG-DSC, XRD, SEM-EDS, and low-field NMR techniques. The results showed that the addition of barite increases the apparent density of ceramsite but decreases its strength. The ceramsite with 60 % barite calcined at 1320°C has a density of 3120 kg/m3, water adsorption of 11.19 %, and a cylinder compressive strength of 11.2 MPa. The prepared BASC ceramsite exhibits a highly connected pore structure and good water retention capacity at this temperature. The ceramsite has many closely packed celsian and corundum crystallites, which give it good mechanical strength. Finally, the gamma-ray attenuation and autogenous shrinkage of UHPC prepared with this ceramsite was tested. The linear attenuation coefficient of the BASC-UHPC is 0.176 cm−1, comparable to UHPC prepared with lead glass. The BASC replacement for quartz sand reduces the 28d autogenous shrinkage of UHPC by 55.0 %. The research results can guide the application of BAS-based ceramsite in radiation-shielding ultra-high performance concrete.

Quantitative characterization of 3D pore structures and percolation characteristics in bioturbated reservoir media based on X-ray micro-CT: a case study of the Neogene Sanya Formation in the Qiongdongnan Basin, Northern South China Sea

Organisms alter the primary texture of sediments, leading to alteration in petrophysical properties mediated by a textural and mineralogical contrast between burrow-fill and sediment host, which affects reservoir properties and fluid flow characteristics. In this article, in order to understand the microscopic pore structure and flow state of fluids in microscopic pores of bioturbated reservoirs, Ophiomorpha-bearing bioturbated reservoirs in the Neogene Sanya Formation of the Qiongdongnan Basin in the northern South China Sea were selected to research. Micro-CT was applied to scan selected core plugs, and a 3D pore structure model was established. The geometric characteristics of the microscopic pore structure were quantitatively and visually characterized by a modified maximal ball algorithm, and connectivity analysis of the pore structure was carried out. Numerical simulations of the percolation characteristics of the analyzed bioturbated reservoir samples were performed using digital core software (Avizo) and multi-physics field simulation software (Comsol). The results show that: (1) 3D pore structures reveal that pore volume, pore area, pore equivalent radius, throat area, throat equivalent radius and throat length have a large distribution range; among them, the pore volume has the largest distribution range, which can vary by six orders of magnitude, indicating that the pore size distribution of the bioturbated reservoir is uneven and has strong heterogeneous characteristics; (2) the connected pore structure is very complex, and as the equivalent radius of connected pore increases, the coordination number also gradually increases, the better the connectivity. Numerical percolation simulation results also suggested that larger connected pore space plays a key role in the effective permeability of the reservoir. This study has important implications for analyzing the modification effect of bioturbation on oil and gas reservoirs, and enhancing production and recovery in the study area.

Comprehensive Analysis of Connectivity and Permeability of a Pore-Fracture Structure in Low Permeability Seam of Huainan-Huaibei Coalfield.

The connectivity and permeability of the coal seam pore structures control the occurrence and migration of coalbed methane. Coal samples were used from Huainan-Huaibei to reconstruct three-dimensional models of the pores and an equivalent pore network model, Statistical pore structure characteristic parameters. The pore structure of the coal reservoir was analyzed from the direction of multidimensional and multiangle. It shows that based on quantitative analysis, the representative Elementary volume of 500 × 500 × 500 was the most suitable experimental volume. The Y-axis direction of the Renlou sample had poor pore connectivity compared to that of other samples. Large volume connected pores dominated their pore systems. In terms of coal sample pore connectivity, the coal samples from the Liuzhuang and Qidong regions had pore connectivity better than those from the other regions. The pore connectivity of the Liuzhuang coal samples was the best. In terms of coal permeability, the Liuzhuang sample had better permeability than the other three samples, and the permeability was the best in the Y-axis direction. For all the combinations of the different types of throats, the shorter the throat, the greater the equivalent radius and the better the permeability. Conversely, the worse the permeability. During gas injection production, the closer the gas injection area was to the gas injection well, the poorer the connectivity and the lower the permeability over time. Near the production area, where the CO2 did not reach the production area, the fracture porosity and effective connected porosity of the coal reservoir increased over time. When CO2 reached the production area, the change in its connected pore structure was consistent with the change in the connected pores in the gas injection area. With this study, the coal seam pore structure on a microscale was characterized. A comprehensive analysis of the coal reservoir pore connectivity and permeability was completed. The study results are significant for the exploration and development of coalbed methane in the Huainan-Huaibei coalfield.

Cell-free chitosan/silk fibroin/bioactive glass scaffolds with radial pore for in situ inductive regeneration of critical-size bone defects

Tissue-engineered is an effective method for repairing critical-size bone defects. The application of bioactive scaffold provides artificial matrix and suitable microenvironment for cell recruitment and extracellular matrix deposition, which can effectively accelerate the process of tissue regeneration. Among various scaffold properties, appropriate pore structure and distribution have been proven to play a crucial role in inducing cell infiltration differentiation and in-situ tissue regeneration. In this study, a chitosan (CS) /silk fibroin (SF) /bioactive glass (BG) composite scaffold with distinctive radially oriented pore structure was constructed. The composite scaffolds had stable physical and chemical properties, a unique pore structure of radial arrangement from the center to the periphery and excellent mechanical properties. In vitro biological studies indicated that the CS/SF/BG scaffold could promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and the expression of related genes due to the wide range of connected pore structures and released active elements. Furthermore, in vivo study showed CS/SF/BG scaffold with radial pores was more conducive to the repair of skull defects in rats with accelerated healing speed during the bone tissue remodeling process. These results demonstrated the developed CS/SF/BG scaffold would be a promising therapeutic strategy for the repair of bone defects regeneration.

Comparing petrophysical properties and pore network characteristics of carbonate reservoir rocks using micro X-ray tomography imaging and microfacies analyses

Carbonate rocks have complex pore structures as a result of sedimentological and diagenetic processes. We investigated the pore network of four carbonate rock samples originating from an oil well in Hungary. Two samples were from the productive part of the Sarmatian limestone, and the other two were from the dry interval. We employed X-ray computed tomography (micro-XCT) in combination with lab measurements and microfacies analysis. To achieve accurate X-ray image segmentation we investigated and compared several segmentation techniques, including entropy and clustering. We then employed the Naïve Bayes classifier and tenfold cross-validation to assess the accuracy of our results. Our study achieved high accuracy with the type-2 fuzzy entropy technique on various metrics, including precision and recall. The comparison between the measured helium porosity and image-derived porosity showed a close match. Micro-XCT measurements revealed connected pore structure in the productive interval, compared to isolated pores in the dry interval. Microfacies analyses indicated that both the rocks of the productive and dry intervals were deposited in a marine environment, but different diagenetic processes altered the sediment into productive and dry rocks, respectively. The diagenesis of the productive rocks occurred in a meteoric phreatic environment, where secondary pores were created (porosity enhancement). In contrast, the dry rocks underwent meteoric vadose and marine diagenesis, where all previously created pores were filled with cement (porosity destruction). Our study highlights the importance of accurately characterizing the pore network of carbonate rocks, which can aid in understanding reservoir properties and predicting fluid flow behavior.

Hard-templated macroporous alumina with thick mesoporous walls: The key factors of pore formation

This paper focuses on the key factors contributing to pore formation in hard-templated macroporous alumina. Special attention is paid to the formation of a connected pore structure. Two series of samples were prepared, each with different content of the polymeric template. The pore structure of alumina was designed using polystyrene and acrylic copolymers as hard templates. Alumina differed in crystallite morphology (round-like and rod-like) and pore structure (bottleneck-like and slit-like). The templates differed in particle size (100 and 250 nm) and physical state (powder and suspension). All the samples were characterized by N2 adsorption, Hg porosimetry, XRD, and SEM. The data obtained indicate that a hard template made of polymeric particles has the following functions: fixing the pore size and shape, sintering small pores of the material, and creating additional channels to connect macropores. Regardless of the type of polymeric template and Al2O3 precursor, a connected pore system can be formed by adding more than 20 wt% of the template.

Synthesis and properties of foam glass-ceramics from granite tailings by using SiC and MnO2 as the mixed foaming agent

Foam glass-ceramics were successfully prepared with the powder sintering method using granite tailings as the main raw material, and silicon carbide (SiC), and manganese dioxide (MnO2) as the mixed foaming agent. The effects of the mixed foaming agent and sintering temperature on the crystalline phase, pore-wall structure, and the properties of the prepared foam glass-ceramics were systematically studied. Moreover, the foaming mechanism of the foam glass-ceramics prepared by using the mixed foaming agent was revealed. The results showed that, with a decrease of SiC content, the thermal conductivity and compressive strength decreased, and with an increase of MnO2 content, a special connected pore structure formed in the pore wall of the sample. The optimum mass ratio of MnO2: SiC in the mixed foaming agent was 1: x (x = 3‒7). Foam glass-ceramics with good thermal insulation performance, a bulk density of 0.35–0.50 g/cm3, a porosity of 85.05–88.12%, a thermal conductivity of 0.037–0.046 W/(m·K), and high compressive strength (0.46–3.11 MPa) were obtained at the sintering temperature of 880 °C.

Pore Structure and Permeability Characterization of Tight Sandstone Reservoirs: From a Multiscale Perspective

Due to the influence of a sedimentary environment, sandstone characteristics, diagenesis, and geological structure, the complexity and heterogeneity of the pore structure in tight sandstone reservoirs act as key barriers for accurate characterization of the influence of different pore microparameters on reservoir physical properties. This paper obtained different scale microscopic pore–throat parameters through mercury intrusion porosimetry (MIP) and digital core reconstruction models. According to the connectivity of different scale pores, connected pore structure parameters, and pore fractal dimension, the pore structure characteristics of tight sandstone reservoirs were evaluated. Subsequently, through partial correlation analysis, the contribution rate of different scale connected pore parameters to permeability and porosity was clarified. Then, a multiparameter fitting equation for the absolute permeability and porosity of the rock was obtained through multiple regression analysis. The analysis results show that (1) the connected pores of tight sandstone reservoirs are mainly mesopores, with the pore radius distribution between 1 and 3 μm, and throat radius distribution between 0 and 2 μm. (2) The complexity of the pore structure in tight sandstone reservoirs is most strongly correlated with the fractal dimension of the pore structure at the mesoporous scale. (3) The pore radius and throat length at the mesoporous scale have the strongest correlation with the absolute permeability of the rock, and the pore radius at the mesoporous scale has the strongest correlation with the porosity of the rock. (4) The multiparameter fitting equation established by multiple regression analysis quantitatively and qualitatively analyzed the impact of microscopic parameters of the pore–throat structure at different scales on reservoir properties, achieving the purpose of predicting the absolute permeability and porosity of the tight sandstone reservoir. It provides guidance for the study of the pore structure and permeability characteristics of tight sandstones.

Preparation of a novel high-performance lignin-based anionic adsorption resin for efficient removal of Cr(VI) in aqueous solutions

To remove Cr(VI) in water, a novel lignin-based anionic adsorption resin epichlorohydrin cross-linking lignin grafted by diethylenetriamine (E-DAL) was prepared by the direct cross-linking and curing of alkali lignin grafted by diethylenetriamine in aqueous solutions. Under the determined optimum synthesis conditions, E-DAL with higher nitrogen (7.46%) and lignin (32.78%) contents was obtained. Structural and physicochemical measurement results showed E-DAL was a macroporous resin, having a regular connected pore structure with porosity of 67.48% and pore size of 615.6 nm, also strong hydrophilicity, excellent acid-alkaline resistance and thermal stability. Adsorption experiment results indicated the adsorption isotherm of E-DAL to Cr(VI) was well-described by Langmuir model. E-DAL showed a higher adsorption capacity to Cr(VI), and the fitted maximum adsorption capacity reached up to 775.2 mg/g. Pseudo-second-order model could fit this adsorption process well, suggesting its chemisorption characteristics. The calculated thermodynamic parameters indicated a spontaneous and endothermic adsorption of E-DAL to Cr(VI). Dynamic column adsorption results showed E-DAL could completely remove Cr(VI) in wastewater. This whole preparation process only used a very small amount of cheaper amination agent and was relatively low-cost. This work provided efficient technical supports for the structural design of high-performance lignin-based anionic adsorption materials in water treatment field.

A novel method combining VAT photopolymerization and casting for the fabrication of biodegradable Zn–1Mg scaffolds with triply periodic minimal surface

Zinc alloy porous scaffolds are expected to be the next generation of degradable orthopedic implants attributed to their suitable degradation rate. However, a few studies have thoroughly investigated its applicable preparation method and functionality as an orthopedic implant. This study fabricated Zn–1Mg porous scaffolds with triply periodic minimal surface (TPMS) structure by a novel method combining VAT photopolymerization and casting. As-built porous scaffolds displayed fully connected pore structures with controllable topology. The manufacturability, mechanical properties, corrosion behaviors, biocompatibility, and antimicrobial performance of the bioscaffolds with pore sizes of 650 μm, 800 μm, and 1040 μm were investigated, and then compared and discussed with each other. In simulations, the mechanical behaviors of porous scaffolds exhibited the same tendency as the experiments. In addition, the mechanical properties of porous scaffolds as a function of degradation time were studied through a 90-day immersion experiment, which can provide a new option for analyzing the mechanical properties of porous scaffolds implanted in vivo. The G06 scaffold with lower pore size presented better mechanical properties before and after degradation compared with G10. The G06 scaffold with the pore size of 650 μm revealed good biocompatibility and antibacterial properties, which makes it possible to be one of the candidates for orthopedic implants.

Ablation behavior of PEO coatings on niobium alloy

To improve the ablation resistance of niobium alloy, plasma electrolytic oxidation (PEO) was introduced to fabricate coatings with different pore structures on niobium alloy by adjusting the applied voltage. The pore volume and shape were investigated by X-ray computed tomography, and the ablation behavior of PEO coatings was also thoroughly discussed. It was found that the ablation behavior of PEO coatings could be divided into the crack propagation stage and the coating peeling stage, which are related to the specific pore structure and ablative oxidation. The stress concentration in the pore tip increased by 60.61% as the pore shape transforms from isolated pores to connected pores, accelerating crack initiation and propagation. Subsequently, oxygen erodes the substrate through connected pores and cracks, which is accelerated by high overall porosity (23.4%) and severe crack propagation, followed by ablative oxidation of the substrate leading to the eventual peeling of the PEO coating. After 15 min of ablation, no coating peeling occurred for the isolated pore structure, while the coating peeling area of the connected pore structure reached 82.1%. Thus, the isolated pores could transfer stress and inhibit further diffusion of oxygen into the coating, improving the ablation resistance of PEO coatings. It is expected that this research would provide feasible ideas for the design and fabrication of ablation-resistant coatings on niobium alloy.

Study on Strength and Microstructure of Red Clay Reinforced by F1 Ionic Soil Stabilizer

High-liquid limit red clay has poor engineering characteristics, namely poor water stability, low strength, and large expansion and contraction deformation. The clay may be reinforced with an F1 ionic soil stabilizer. The engineering characteristics of this reinforced clay were studied, specifically concerning its basic physical parameters, shear strength parameters, and micropore structure. The F1 ionic soil stabilizer significantly improved the water sensitivity, compaction characteristics, and shear strength of red clay. We determined that the optimal F1 ionic soil stabilizer mix was 0.5 L/m3, resulting in a reinforced clay with plastic limit increased by 45.74%, optimal moisture content increased by 12.12%, maximum dry density increased by 5.8%, liquid limit reduced by 8.4%, plasticity index reduced by 43.8%, infiltration coefficient reduced by 41.8%, cohesion increased 1.64-fold, and internal friction angle increased 1.30-fold. Freeze-thaw cycles reduced the shear strength parameters of the reinforced red clay, although even after 15 cycles, it still had 18.4% higher cohesion and 57.1% higher internal friction angle than undisturbed red clay. The F1 ionic soil stabilizer significantly reduced the pore size and area of red clay, the complex connected pore structure is adjusted to a more regular structure. The reinforced clay had 56.64% lower pore area ratio, 32.27% lower average Feret diameter, and 2.43% lower fractal dimension.

Separator Dependency on Cycling Stability of Lithium Metal Batteries Under Practical Conditions

Development of practical lithium (Li) metal batteries (LMBs) remains challenging despite promises of Li metal anodes (LMAs), owing to Li dendrite formation and highly reactive surface nature. Polyolefin separators used in LMBs may undergo severe mechanical and chemical deterioration when contacting with LMAs. To identify the best polyolefin separator for LMBs, this study investigated the separator‐deterministic cycling stability of LMBs under practical conditions, and redefined the key influencing factors, including pore structure, mechanical stability, and chemical affinity, using 12 different commercial separators, including polyethylene (PE), polypropylene (PP), and coated separators. At extreme compression triggered by LMA swelling, isotropic stress release by balancing the machine direction and transverse direction tensile strengths was found to be crucial for mitigating cell short‐circuiting. Instead of PP separators, a PE separator that possesses a high elastic modulus and a highly connected pore structure can uniformly regulate LMA swelling. The ceramic coating reinforced short‐circuiting resistance, while the cycling efficiency degraded rapidly owing to the detrimental interactions between ceramics and LMAs. This study identified the design principle of separators for practical LMBs with respect to mechanical stability and chemical affinity toward LMAs by elucidating the impacts of separator modification on the cycling performance.

A novel preparation of high permeation SiC supports for NaA zeolite membrane by in situ reaction bonding

The performance of zeolite membrane supports directly determines the synthesis performance and industrial application of zeolite membranes. In this study, a novel and high permeation SiC supports for NaA zeolite membrane were prepared by carrying out in situ reaction bonding at high temperature in the air atmosphere to coat the SiC particles with aluminum sol. The effects of process parameters on the formation of porous structure of SiC supports were systematically investigated, and the underlying mechanism was explored. During the sintering process, high-temperature Al2O3 from aluminum sol reacted with SiO2 generated by oxidation of the surface of SiC particles to form mullite, which exhibited excellent chemical stability and improved the mechanical properties and chemical stability of the supports. The porous SiC supports for zeolite membrane displayed obvious three-dimensional connected pore structure, with smooth inner surface of the pores and obvious connection neck between the particles. The porous SiC supports for zeolite membrane showed good in situ mullite bonding between the particles, and high permeability. It has a porosity of 36.3%, an average pore size of 1.42 µm and a bending strength of 32.4 MPa. All these figures indicate good comprehensive properties that are consistent with the rigorous requirements of zeolite membrane synthesis and industrial application.

Optimized pore structure and high permeability of metakaolin/fly-ash-based geopolymer foams from Al– and H2O2–sodium oleate foaming systems

Geopolymer foams have been widely studied as adsorbents owing to their high specific surface areas, high heavy metal immobilization efficiencies, low cost, environmental friendliness, and resource-recycling benefits. In this study, geopolymer foams with different pore structures were prepared from Al– and H2O2–sodium oleate foaming systems, and their chemical properties, pore structures, and permeabilities were characterized. The effects of the foaming agent type and surfactant content on the crystal structure and chemical bonding of the materials were analyzed by X-ray diffraction analysis and Fourier-transform infrared spectroscopy, and the pore morphology and structural characteristics were characterized by morphological observations, three-dimensional (3D) reconstruction, and compression tests. Numerical simulations were also carried out to study the structural characteristics of the 3D-reconstructed pores. Furthermore, variations in the permeability coefficient and flow characteristics were tested and analyzed by experiments and simulations. The pores in the geopolymer from the H2O2–sodium oleate foaming system tended to be more connected, whereas those in the Al–sodium oleate geopolymers were more complete and closed. The highly connected pore structure facilitates the even diffusion of the solution and effectively increases the amount of adsorption sites. These properties are significant for adjusting the adsorption capacity of geopolymer foams as adsorption monoliths.

In vitro and in vivo study of magnesium containing bioactive glass nanoparticles modified gelatin scaffolds for bone repair

Magnesium containing bioactive glass nanoparticles modified gelatin scaffolds (MBGNs/Gel scaffolds) have shown recently the potential for bone regeneration due to its good biocompatibility, bioresorbability and bioactivity. Nevertheless, its use is limited by its complicated manufacturing process and a relatively expensive price. In this study, MBGNs were prepared by sol–gel process. The MBGNs/Gel was synthesized by a simple immersion method. SEM, transmission electron microscopy and dynamic light scattering analysis showed that the particles had spherical morphology with mean particle size of 100 nm. The MBGNs/Gel scaffolds were observed by SEM. The scaffolds showed connected pore structure with pore size ranging from 100 to 300 μm. SEM images with high magnification showed the existence of MBGNs on the surface of micro-pores. The ion release results revealed the release of Mg, Ca and Si elements from the MBGNs. MTT assay and cytotoxicity studies indicated that, the scaffolds provide a suitable ion related micro-environment for cell attachment and spreading. The Reverse Transcription-Polymerase Chain Reaction (RT-PCR) results showed the scaffolds could promote the osteogenesis of MC3T3-E1. The in vivo study also showed higher amount of new bone and trabecular bone which indicated excellent bone induction and conduction property of modified scaffolds. So, the developed MBGNs/Gel scaffolds are a potential candidate for bone regeneration applications.

Liquid-Assisted Electrospinning Three-Dimensional Polyacrylonitrile Nanofiber Crosslinked with Chitosan

Electrospinning has become a popular nanotechnology for the fabrication of tissue engineering scaffolds, which can precisely regulate fiber diameter and microstructure. Herein, we have prepared a three-dimensional polyacrylonitrile (PAN) nanofiber by liquid-assisted electrospinning. The spacing between PAN nanofibers can reach to 15-20 μm, as the uniform internally connected pore structure can be formed, through the regulation of parameters. Furthermore, the chitosan attached to the as-prepared nanofibers gives the material antibacterial effect and increases its biocompatibility. Meanwhile, the special structure of chitosan also provides the possibility for further loading drugs in dressings in the future. This newly developed nanocomposite seems to be highly suitable for wound healing due to its unique properties of biodegradability, biocompatibility, and antimicrobial effectiveness.

Evolving thermal conductivity upon formation and decomposition of hydrate in natural marine sediments

An insufficient heat supply has been recognized to majorly hinder the hydrate decomposition which is endothermic and thereby requires large amount of heat to sustain. Consequently, the thermal properties of the sediments play a vital role in the heat transfer process internally. Yet their evolution during hydrate formation and decomposition is complicated which couples phase transition, multiphase flow and component migration; relating knowledge still remain limited. Here, we report on a point-heat-source based measurement of local thermal conductivity of natural fine-grained sediments containing hydrates. The results show a significant effect of compaction on the effective thermal conductivity arising from the compressibility of the silty sediments. The evolution of components and their morphological behavior were found to majorly contribute to the variations of the thermal conductivity during hydrate formation, decomposition and reformation. A local icing and reformation of hydrate could also result in an enhancement of thermal conductivity benefiting from the better connected pore structure. Classic effective medium models were evaluated using our measured data; a hybrid fitting model by combining the self-consistent models was proposed, and the feasibility of the fitting model was verified using the data from the natural reservoir. The results of this study could provide insights into the effect of evolving hydrate phase on the resulting effective thermal conductivity of natural sediments; the findings would be helpful in a potential enhancement of the heat transfer process during gas production from hydrate reservoir to achieve an improved gas productivity.