Correlation between Pitch Impregnation Pressure and Pore Sizes of Graphite Block

This study aimed to investigate the effect of impregnation pressure on the decrease in porosity of impregnated bulk graphite. The correlation between pitch impregnation behavior and the pore sizes of the bulk graphite block was studied to determine the optimal impregnation pressure. The densities and porosities of the bulk graphite before and after pitch impregnation under various pressures between 10 and 50 bar were evaluated based on the Archimedes method and a mercury porosimeter. The density increased rates increased by 1.93–2.44%, whereas the impregnation rate calculated from the rate of open porosity decreased by 15.15–24.48%. The density increase rate and impregnation rate were significantly high when the impregnation pressures were 40 and 50 bar. Compared with impregnation pressures of 10, 20, and 30 bar, the minimum impregnatable pore sizes with impregnation pressures of 40 and 50 bar were 30–39 and 24–31 nm, respectively. The mercury intrusion porosimeter analysis results demonstrated that the pressure-sensitive pore sizes of the graphite blocks were in the range of 100–4500 nm. Furthermore, the ink-bottle-type pores in this range contributed predominantly to the effect of impregnation under pressure, given that the pitch-impregnated-into-ink-bottle-type pores were difficult to elute during carbonization.

Macroporous methacrylated hyaluronic acid hydrogel with different pore sizes for in vitro and in vivo evaluation of vascularization

Vascularization of thick hydrogel scaffolds is still a big challenge, because the submicron- or nano-sized pores seriously restrict endothelial cells adhesion, proliferation and migration. Therefore, porous hydrogels have been fabricated as a kind of promising hydrous scaffolds for enhancing vascularization during tissue repairing. In order to investigate the effects of pore size on vascularization, macroporous methacrylated hyaluronic acid (HAMA) hydrogels with different pore sizes were fabricated by a gelatin microspheres (GMS) template method. After leaching out GMS templates, uniform and highly interconnected macropores were formed in hydrogels, which provided an ideal physical microenvironment to induce human umbilical vein endothelial cells (HUVECs) migration and tissue vascularization. In vitro results revealed that macroporous hydrogels facilitated cells proliferation and migration compared with non-macroporous hydrogels. Hydrogels with middle pore size of 200-250 μm (HAMA250 hydrogels) supported the best cell proliferation and furthest 3D migration of HUVECs. The influences of pore sizes on vascularization were then evaluated with subcutaneous embedding. In vivo results illustrated that HAMA250 hydrogels exhibited optimum vascularization behavior. Highest number of newly formed blood vessels and expression of CD31 could be found in HAMA250 hydrogels rather than in other hydrogels. In summary, our results concluded that the best pore size for endothelial cells migration and tissue vascularization was 200-250 μm. This research provides a new insight into the engineering vascularized tissues and may find utility in designing regenerative biomaterial scaffolds

Monitoring of the Variation in Pore Sizes of Woven Geotextiles with Uniaxial Tensile Strain

Characteristic pore-opening size O95 or O90 has been widely used in the filter design of woven geotextiles. These manufactured products have different pore size proportions of large pore diameters, medium pore diameters, and small pore diameters, respectively. Therefore, uncertainties still exist regarding the prediction of geotextile pore diameter variations under the uniaxial tensile strain. This paper investigates the variations in five characteristic pore-opening sizes O95, O80, O50, O30, and O10, with uniaxial tensile strain by using the image analysis method. The large pore diameters, medium pore diameters, and small pore diameters show different variation behaviors as the uniaxial tensile strain increases. Fifteen specific pores are selected and then their pore diameter variations are monitored under each tensile strain of 1%. The colorful pore size distribution diagram is a visual way to identify the variation of pores arranged in the tension direction (warp direction) and the direction perpendicular to tensile loads (weft direction). The various pore diameters are proved to agree well with the bell-shaped Gaussian distribution. The results exhibit an accurate prediction of the variation in large pore sizes, medium pore sizes, and small pore sizes, respectively, for all tested woven geotextiles with uniaxial tensile strain.

Statistical Analysis of Synthesis Parameters to Fabricate PVDF/PVP/TiO2 Membranes via Phase-Inversion with Enhanced Filtration Performance and Photocatalytic Properties

Non-solvent induced phase-inversion is one of the most used methods to fabricate membranes. However, there are only a few studies supported by statistical analysis on how the different fabrication conditions affect the formation and performance of membranes. In this paper, a central composite design was employed to analyze how different fabrication conditions affect the pure water flux, pore size, and photocatalytic activity of polyvinylidene fluoride (PVDF) membranes. Polyvinylpyrrolidone (PVP) was used to form pores, and titanium dioxide (TiO2) to ensure the photocatalytic activity of the membranes. The studied bath temperatures (15 to 25 °C) and evaporation times (0 to 60 s) did not significantly affect the pore size and pure water flux of the membranes. The concentration of PVDF (12.5 to 17.5%) affected the viscosity, formation capability, and pore sizes. PVDF at high concentrations resulted in membranes with small pore sizes. PVP affected the pore size and should be used to a limited extent to avoid possible hole formation. TiO2 contents were responsible for the decolorization of a methyl orange solution (10−5 M) up to 90% over the period studied (30 h). A higher content of TiO2 did not increase the decolorization rate. Acidic conditions increased the photocatalytic activity of the TiO2-membranes.

Development of a Mesoporous Silica-Supported Layered Double Hydroxide Catalyst for the Reduction of Oxygenated Compounds in E. grandis Fast Pyrolysis Oils

Biomass fast pyrolysis oil is a potential renewable alternative to fossil fuels, but its viability is constrained by its corrosiveness, low higher heating value and instability, caused by high oxygenate concentrations. A few studies have outlined layered double hydroxides (LDHs) as possible catalysts for the improvement of biomass pyrolysis oil characteristics. In this study, the goal was to reduce the concentration of oxygen-rich compounds in E. grandis fast pyrolysis oils using CaAl- and MgAl- LDHs. The LDHs were supported by mesoporous silica, synthesised at different pHs to obtain different pore sizes (3.3 to 4.8 nm) and surface areas (up to 600 m2/g). The effects of the support pore sizes and use of LDHs were investigated. GC/MS results revealed that MgAl-LDH significantly reduced the concentrations of ketones and oxygenated aromatics in the electrostatic precipitator oils and increased the concentration of aliphatics. CaAl-LDH had the opposite effect. There was little effect on the oxygenate concentrations of the heat exchanger oils, suggesting that there was a greater extent of conversion of the lighter oil compounds. Bomb calorimetry also showed a marked increase in higher heating values (16.2 to 22.5 MJ/kg) in the electrostatic precipitator oils when using MgAl-LDH. It was also found that the mesoporous silica support synthesised at a pH of 7 was the most effective, likely due to the intermediate average pore width (4 nm).

Microstructure evolution of young sea ice from a Svalbard fjord using micro-CT analysis

We analysed the three-dimensional microstructure of sea ice by means of X-ray-micro computed tomography. Microscopic (brine- and air- pore sizes, numbers and connectivity) and macroscopic (salinity, density, porosity) properties of young Arctic sea ice were analysed. The analysis is based on ice cores obtained during spring 2016. Centrifuging of brine prior to CT imaging has allowed us to derive confident relationships between the open, vertically connected and total porosity of young sea ice at relatively high temperatures. We analysed the dependence of the microscopic properties on vertical position and total brine porosity. Most bulk properties (salinity, density) and pore space properties (pore sizes and their distribution) show a strong dependence on total brine porosity, but did not change significantly over the course of the field work. However, significant changes were observed for pore numbers (decreasing over time) and pore connectivity (increasing over time). CT-based salinity determinations are subject to larger than standard uncertainties (from conductivity), while the CT method yields important information about the salinity contributions from closed and open pores. We also performed a comparison of CT-based air porosity with calculations based on density from hydrostatic weighing. The consistency is encouraging and gives confidence to our CT-based results.

Confinement in Extruded Nanocomposites Based on PCL and Mesoporous Silicas: Effect of Pore Sizes and Their Influence in Ultimate Mechanical Response

In this study, nanocomposites based on polycaprolactone (PCL) and two types of mesoporous silicas, MCM-41 and SBA-15, were attained by melt extrusion. The effect of the silica incorporated within the PCL matrix was observed, firstly, in the morphological characteristics and degradation behavior of the resultant composites. DSC experiments provided information on the existence of confinement in the PCL–SBA-15 materials through the appearance of an additional small endotherm, located at about 25–50 °C, and attributed to the melting of constrained crystallites. Displacement to a slightly lower temperature of this endothermic event was observed in the first heating run of PCL–MCM-41 composites, attributed to the inferior pore size in the MCM-41 particles. Thus, this indicates variations in the inclusion of PCL chains within these two mesostructures with different pore sizes. Real-time variable-temperature small-angle X-ray scattering (SAXS) experiments with synchrotron radiation were crucial to confirm the presence of PCL within MCM-41 and SBA-15 pores. Accurate information was also deduced from these measurements regarding the influence of these two mesoporous MCM-41 and SBA-15 silicas on PCL long spacing. The differences found in these morphological and structural features were responsible for the ultimate mechanical response exhibited by the two sets of PCL nanocomposites, with a considerably higher increase of mechanical parameters in the SBA-15 family.

Integration of NMR Factor Analysis, Multifunction LWD Measurements, and T2 Modeling Improve Fluid Identification in Complex Carbonate Reservoirs

Carbonate environments are complex by nature and the characterization, based on their petrophysical properties, has always been challenging due to the pore heterogeneity. In this paper, we present the integration of factor analysis applied to while-drilling Nuclear Magnetic Resonance (NMR) data, full-suite data from a multifunction logging-while-drilling (LWD) tool, and modeling of the NMR T2 transverse relaxation time to improve the fluid typing interpretation in complex carbonate reservoirs. The interpretation results are essential for perforation and completion decisions in a high-angle development well. The carbonate reservoirs in this case study are within the Kujung formation in the East Java Basin. Kujung I is a massive carbonate reservoir with abundant secondary porosity, while Kujung II and III consist of interbedded thin carbonate reservoirs and shale layers. High uncertainty in identifying the fluid type existed in the Kujung II and III formations due to the presence of multiple fluids in the reservoir, the effect of low water salinity, as well as pore heterogeneity and diagenesis. Due to the high-angle well profile, LWD tool conveyance became the primary method for data acquisition. NMR while drilling and multifunction LWD tools were run on the same drilling bottomhole assembly (BHA) to provide complete formation evaluation and fluid identification. The NMR factor analysis technique was used to decompose the T2 distribution into its porofluid constituents. Thorough T2 peaks modeling was performed to interpret the fluid signatures from the factor analysis results. Borehole images, caliper, triple-combo, density-magnetic resonance gas corrected porosity (DMRP), as well as time-lapse data were evaluated to identify the presence of secondary porosity and narrow down the T2 fluid signatures interpretation. Each of the porofluid signatures were identified and validated in the Kujung I formation with its proven gas and thick water zone. These signatures were then used as references to interpret the fluid types in the Kujung II and III formations. Gas was identified by a low-amplitude peak in the shorter T2 range between 400 ms to 1 s. Oil or synthetic oil-based mud (SOBM) filtrate was indicated by a high-amplitude peak in the longer T2 range (>1.5 s). The water signatures are very much dependent on the underlying pore sizes. Larger pore sizes will generate longer T2 values, which could fall into the same T2 range as hydrocarbon. For that reason, it is important to combine the NMR porofluid signatures interpretation with other LWD data to restrict the fluid type possibilities. This integrated methodology has successfully improved the fluid type interpretation in the Kujung II and III thin carbonate reservoir targets and was confirmed by the actual production results from the same well. This case study presents excellent integration of LWD NMR with other LWD data to reduce fluid type uncertainties in complex carbonate reservoirs, which were unresolved by conventional interpretation methods. Based on this success, a similar integrated NMR factor analysis method can be applied to future development wells in the same field.