Decrease In Average Pore Size Research Articles

INFLUENCE OF WIRE FEED RATE OF HIGH-SPEED ELECTRIC ARC METALLISATION ON STRUCTURE AND CORROSION PROPERTIES OF 30HGSA STEEL COATINGS

The study examines the porosity characteristics, corrosion analysis, and microstructure of iron-based coatings sprayed by supersonic arc metallisation in order to understand the regularity of the influence of the parameters by wire feed rate dependence. The performance of iron-based coatings depends on the integrity of the coating structure. Optimisation of arc spraying parameters allows minimising defects (pores, grain boundaries, unmelted particles, oxides and microcracks) that deteriorate coating properties. At high current levels, the microstructure of the coatings becomes more dense and the particle size decreases, also the average pore size decreases. As the wire feed rate increases, the value of current increases, which leads to the release of more heat energy at the arc to melt the wire and consequently favours the formation of dense coatings with low porosity.

High-temperature dynamic failure behavior and compressive mechanical properties of alumina porous ceramic with various pore sizes

The dynamic compressive mechanical properties of alumina porous ceramic with various average pore sizes are tested at strain rates and temperatures ranging from 0.01 s−1 to 2900 s−1 and 20 °C to 850 °C, respectively. The corresponding 3d Voronoi models are employed to simulate the meso‑characteristics of cells and failure characteristics of alumina porous ceramic in multiscale. The failure in macroscale of quasi-static compression is fragmentation, and that of dynamic compression is comminution. But in mesoscale, the failure, both of quasi-static and dynamic compression, is the fracture of cell walls. Its dynamic strength increases with the increase of strain rate, but decreases with the increase of temperature and average pore size. The increase in temperature and average pore size leads to a decrease in its strain rate sensitivity. Its Young's modulus is not sensitive to the strain rate, but increases with the decrease of average pore size, and decrease with the increase of temperature, which is presented as a temperature and average pore size dependent function. The strain rate and temperature effects are also presented by average pore size dependent functions, respectively. A constitutive model is proposed based on them. It shows that the constitutive model fits well with the experimental results.

Preparation and properties of mullite ceramic-based porous aggregates with high closed porosity utilizing low-voltage electroceramics waste

Mullite ceramic-based porous aggregates, known for their high strength and closed porosity, are widely utilized in engineering. This study successfully prepared mullite-ceramic-based porous aggregates from low-voltage electroceramics waste, investigating the impact of pore-forming agents, bauxite chamotte, and sintering temperature on the physical properties and cold compressive strength. Finally, a mechanism of closed and open pores formation was proposed. The results show that when 10 wt% activated carbon was added, enhanced particle dispersion and stability in apparent porosity, bulk density, and diameter shrinkage ratio were observed, with an optimal range of activated carbon addition identified at around 10.0 wt%. Furthermore, increasing bauxite chamotte addition from 5.0 wt% to 15.0 wt% at 1000°C promoted mullite nucleation, facilitating mullite crystal formation and reducing the relative content and viscosity of the liquid phase. This led to increased apparent porosity, reduced closed porosity, and a decrease in average pore size. However, stress concentration around surface pores resulted in reduced cold compressive properties. The sintering temperature was then increased from 900°C to 1200°C using 10.0 wt% activated carbon and 15 wt% bauxite chamotte, leading to changes in crystallinity and porosity. At 1100°C, isolated islands of the liquid phase between grain boundaries resulted in the highest cold compressive strength and bulk density, while further heating to 1200°C led to a reduction in these properties due to excess liquid phase filling grain boundaries. The formation of closed and open pores is primarily influenced by changes in sintering temperature, which affect the quantity, viscosity, and flowability of the aluminum-silicon liquid phase.

Retention of E-selectin functionalized liposome fanny packs on Jurkat cells following invasion through collagen

Circulating immune cells are an appealing candidate to serve as carriers of therapeutic cargo via nanoparticles conjugated to their surface, for several reasons: these cells are highly migratory and can squeeze through small pores of diameter smaller than their resting size; they are easily accessible in the peripheral blood via minimally invasive IV injection of particles, or can be harvested, processed ex vivo, and reintroduced to the body; they are adept at traveling through the circulation with minimal destruction and thus have access to various tissue beds of the body; and immune cells have built-in signal transduction machinery which allows them to actively engage in chemotaxis and home to regions of the tissue containing tumors, invading microorganisms, or injuries in need of wound healing. In this study, we sought to examine and quantify the degree to which nanoscale liposomes, functionalized with E-selectin adhesion receptor, could bind to a model T cell line and remain on the surface of the cells as they migrate through collagen gels of varying density in a transwell cell migration chamber. It is demonstrated that physiological levels of fluid shear stress are necessary to achieve optimal binding of the E-selectin liposomes to the cell surface as expected, and that CD3/CD28 antibody activation of the T cells was not necessary for effective liposome binding. Nanoscale liposomes were successfully conveyed by the migrating cells across a layer of rat tail type 1 collagen gel ranging in composition from 1 to 3 mg/mL. The relative fraction of liposomes carried through the collagen decreased at higher collagen density, likely due to the expected decrease in average pore size, and increased fiber content in the gels. Taken together, these results support the idea that T cells could be an effective cellular carrier of therapeutic molecules either attached to the surface of nanoscale liposomes or encapsulated within their interior.

Intrinsic and extrinsic contributions in the ferroelectric response of chemically synthesized BiFeO3-xPbTiO3 thin films

Multiferroic (BiFeO3)1−x-(PbTiO3)x (1−x)BF−xPT thin films exhibit very high electromechanical properties in the vicinity of the morphotropic phase boundary (MPB), making them important candidates for use in several modern device applications. However, preparing high-quality (1−x)BF−xPT thin films is challenging due to the high conductivity caused by oxygen vacancies produced during the synthesis process. This study aims to understand the effect of size and porosity density on the electrical properties of (1−x)BF−xPT thin films. A series of (1−x)BF−xPT solid solution thin films were fabricated using the spin-coating method on Pt/TiO2/SiO2/Si(100) substrates through chemical solution deposition. X-ray diffraction studies revealed a polycrystalline structure. Surface SEM images showed that the films have a uniform surface with average grain sizes ranging between 50 and 200 nm and an average film thickness of 1.5 μm. A decrease in average pore size and an increase in the number of pores were observed with the increase in PT concentration in the prepared films. Ferroelectric characterization revealed that the films exhibit room-temperature ferroelectric hysteresis loops. Sources of various contributions to polarization were extracted from hysteresis loops, including true ferroelectric switching and space charge contributions. Thin films with 0.30 < x < 0.45 show higher remanent and saturation polarization values, suggesting that these compositions exhibit the MPB. The highest remanent polarization value (PR = 16.68 μC/cm2) was observed for the thin film with x = 0.40. The correlation between the phase, composition, film morphology, and ferroelectric response is described and discussed.

Adsorptive desulfurization properties of refractory sulfur compounds onto Al2O3-Ga2O3 nanomaterials

The impact of the synthesis method on the structural, textural, and surface properties of the Al2O3-Ga2O3 sample was investigated, and the adsorbents were evaluated for their adsorptive desulfurization properties. The incorporation of Ga atoms into the Al2O3 framework (via SGM) resulted in an increase in specific surface area and pore volume, but a decrease in average pore size. XRF analysis confirmed Ga loading, while SEM-EDS and STEM-EDS techniques revealed well-distributed elements with irregular spherical morphologies. XRD diffractograms confirmed the formation of γ-Al2O3, with a slight shift of diffraction peaks due to the presence of Ga (via SGM), suggesting that Ga atoms are part of the structure. The obtained solids exhibit values in the Freundlich equation that indicate a degree of nonlinearity in adsorption for Al2O3, while Al2O3-Ga2O3(SGM) and Al2O3-Ga2O3(IM) suggest a possible chemical process and favorable adsorption. The small KF values demonstrate weak adsorption on the adsorbents, which can be explained by sulfur-to-metal interaction, π-complexation, and non-specific interactions such as Van der Waals forces. The adsorbent showed the greatest affinity for BT and the least for DBT. The selectivity order from strongest to weakest adsorption was BT: Al2O3-Ga2O3(SGM) > Al2O3-Ga2O3(IM) > Al2O3, and DBT: Al2O3-Ga2O3(IM) > Al2O3-Ga2O3(SGM) > Al2O3.

Study on Damage Mechanism of Waterflooding Development in Weizhou 11-4N Low-Permeability Oilfield

Weizhou 11-4N oilfield is a medium-low-porosity and low-permeability reservoir. The oilfield was initially developed by edge and bottom water energy and then transferred to water injection development. Affected by poor physical properties and heterogeneity of the reservoir, the oilfield appeared in the process of water injection development. When the water injection pressure increases, the water injection volume continues to decrease, and it is difficult to meet the injection requirements. On the basis of the analysis of reservoir heterogeneity, void structure, and clay minerals of reservoir, the water injection compatibility experiment, damage evaluation experiment, and nuclear magnetic resonance-velocity sensitivity experiments were carried out to clarify the damage in the process of oilfield water flooding development. Experiments show that the main causes of damage in Weizhou 11-4N oilfield water flooding development process are water quality incompatibility and strong velocity-sensitive damage. The determination of water type shows that the injected water and formation water are MgCl2 water type and NaHCO3 water type, respectively, under the classification of Surin water type, resulting in the formation of scale with calcium carbonate as the main component in the reservoir. Incompatibility of water quality is an important cause of reservoir damage and scaling. In the reservoir-sensitive flow experiment, the experimental core showed strong velocity sensitivity, the average velocity sensitivity damage rate was 466.31%, and the average critical velocity was 2.98 m/d. Nuclear magnetic resonance experiments show that the core has a significant decrease in average pore size after water flooding. The main damage range is the tiny throat of 0-2 μm. In this paper, the main damage interval of velocity-sensitive damage in the Weizhou 11-4N area and the change trend of void structure after velocity-sensitive experiment are clarified by nuclear magnetic resonance and velocity sensitivity experiments. The main cause of block reservoir damage provides the basis for the oilfield to take targeted measures and provides a guarantee for the efficient development of the subsequent oilfield.

Production of Porous Agarose-Based Structures: Freeze-Drying vs. Supercritical CO2 Drying.

In this work, the effect of two processes, i.e., freeze-drying and supercritical CO2 (SC-CO2) drying, on the final morphology of agarose-based porous structures, was investigated. The agarose concentration in water was varied from 1 wt% up to 8 wt%. Agarose cryogels were prepared by freeze-drying using two cooling rates: 2.5 °C/min and 0.1 °C/min. A more uniform macroporous structure and a decrease in average pore size were achieved when a fast cooling rate was adopted. When a slower cooling rate was performed instead, cryogels were characterized by a macroporous and heterogenous structure at all of the values of the biopolymer concentration investigated. SC-CO2 drying led to the production of aerogels characterized by a mesoporous structure, with a specific surface area up to 170 m2/g. Moreover, agarose-based aerogels were solvent-free, and no thermal changes were detected in the samples after processing.

Ambient pressure drug loading on trimethylchlorosilane silylated silica aerogel in aspirin controlled-release system

Trimethylchlorosilane silylated silica aerogel (TS-SA) was loaded with a model drug, aspirin. TS-SA preparation, drug loading, and drying were performed through ambient pressure techniques in a safe and cheap manner. The sample structure, drug loading, and drug dissolution profiles were characterized by N2 adsorption and desorption analysis, FT-IR spectroscopy, UV absorption spectroscopy, FE-EM, EDX, XRD, and DSC. The characterization results indicated drug molecules are successfully loaded on the entire nanostructure of TS-SA. Specific surface area, total pore volume, and average pore size decrease with drug loading in TS-SA structure, as well as XRD and DSC results are indicating the amorphous state of loaded aspirin. Drug adsorption isotherm was measured and fitted well by the Freundlich model. Drug release kinetics from the samples were also evaluated in 0.1 N HCl (pH 1.2) and phosphate buffer (pH 7.4). The zero-order model, the first-order model, and the Higuchi model were employed to study the release kinetics. Better fitting to the Higuchi model showed that Fick's diffusion governs the aspirin release mechanism. The release rate of loaded samples was slower than the pure drug in both HCl and phosphate buffer. As pure aspirin dissolves totally in 0.1 N HCl and phosphate buffer within 40 min and 20 min, respectively, loaded drug dissolve 35% ± 4 and 80% ± 4 in 0.1 N HCl and phosphate buffer within 100 min. The ambient pressure drug loading on TS-SA could have interesting potential applications in controlled release drug delivery systems.

Peculiarities of palladium-containing MFI-type zeolites as catalysts of isomerization of linear alkanes

Platinum group metals are widely used as a hydrogenating-dehydrogenating component of a number of petroleum refining and petrochemical catalysts, in particular for isomerization of linear alkanes. The main direction in improving the preparation of these catalysts is to reduce their cost by optimizing the metal component amount. However, insufficient attention was paid to the method of introduction of an active metal into the carrier; at the same time, this issue is especially important in case of zeolite catalysts, for which ion exchange can be used in addition to traditional impregnation. Therefore, the purpose of this work was to compare the catalytic efficiencies of Pd-containing MFI zeolites in which metal was introduced by two methods: impregnation from a solution of palladium chloride and ion exchange from tetraamminepalladium(II) chloride in the amount of 0.5 wt.% in terms of pure metal. Study of texture characteristics by nitrogen low-temperature adsorption/desorption technique showed that the specific surface area of samples and the total sorption volume remained practically unchanged, regardless of the procedure of metal component introduction. A significant decrease in average pore size was observed only in case of ion-exchange metal introduction; this indicated the localization of palladium mainly in zeolite pores, which was confirmed by transmission electron microscopy. The stage of transformation from ammonium form to hydrogen one strongly affects the activity of samples, this stage should precede the final stage of metal recovery. The highest yield of hexane isomers of about 46.5 wt.% with the selectivity of 88.7% was observed over a catalyst with Pd introduced by ion-exchange method with the smallest palladium particles (3–7 nm).

Improved electrochemical performance of LiMn1.5M0.5O4 (M=Ni, Co, Cu) based cathodes for lithium-ion batteries

LiMn2O4 and LiMn1.5M0.5O4 (M: Ni, Cu, Co) doped particles have been synthetized by sol-gel. Particles between 50 and 200 nm were obtained with the cubic spinel structure of the LiMn2O4. Ni doping shows a more efficient substitution in the octahedral 16d site, replacing the Mn3+ ion, improving the important drawback of poor cycling behavior of LiMn2O4. The average pore size decrease with the addition of the doped elements in the LiMn2O4 structure from 2.9 to 2.6 nm. Thermal analysis shows that the doped particles present higher thermal stability that the undoped ones. Electrochemical behavior of the cathodes prepared with each of the active materials show that the doping influenced the electrochemical performance of the active material. Thus, a specific capacity of 33, 74, 44 and 53 mAh g−1 (at C) and 74, 89, 59 and 69 mAh g−1 (at C/10) were obtained for LiMn2O4, LiMn1.5Ni0.5O4, LiMn1.5Cu0.5O4 and LiMn1.5Co0.5O4 cathodes, respectively. All cathodes present good electrochemical stability with low capacity fade of 0.5 and 3.1% for LiMn1.5Ni0.5O4 and LiMn1.5Cu0.5O4, respectively, after 50 cycles. These results show an improvement of electrochemical performance for LiMn2O4 doped with Ni, Cu and Co, demonstrating their suitability for lithium-ion battery systems.

Chloride-bearing characteristics of alkali-activated slag mixed with seawater: Effect of different salinity levels

This paper presents the microstructural properties of KOH-activated slag pastes produced with natural seawater under different salinity levels. The seawater-mixed samples exhibit higher 91-day strength compared to the control sample produced with deionized water. Their reduced total porosity and decrease in average pore size are closely related to the strength improvement. The dense microstructure is composed of reaction products resulting from the inclusion of seawater; these include Cl-hydrocalumite, Cl-hydrotalcite, AlClO, K2SO4, CaCO3, calcium aluminum iron oxide carbonate hydroxide hydrate, and aluminum chloride hydrate. In addition, CO32− in the CO3-hydrotalcite and CO3-hydrocalumite is replaced by chloride ions, and then a Cl-bearing phase is formed, leading to a higher bound chloride content. Lastly, in the single ocean current investigated in this study, the strength of seawater-mixed samples is weakly vulnerable to salinity variation.

Processing-Structure-Property Correlation Understanding of Microfibrillated Cellulose Based Dimensional Structures for Ferric Ions Removal

In this research article, wood based microfibrillated cellulose (MFC) was studied to gain a better understanding of the process of dependent network formation. Networking potential and obtained properties of the produced dimensional structures could be controlled using opted processing routes. The fabricated dimensional structure, using freeze-drying (FD) is a highly open and porous network (98% porosity) compared to slightly tight, dense and less porous network produced after pressing at 200kN (96% porosity), followed by vacuum-filtered (VF) networks (33% porosity). The porosity (17%) was further decreased when the casting (CS) method was used, further producing a highly dense and compressed network. High water flux (180.8 ± 11 L/m2h) of pressed freeze-dried (PFD) followed by vacuum-filtered (VF) (11.4 ± 1.9 L/m2h) and casting CS (0.7 ± 0.01 L/m2h) were calculated using device. Furthermore, increased water flux (1.4 fold) of Experimental Paper Machine (XPM) based structures was reported in comparison with CS structures. Pore-sized distribution and surface area were measured using Hg porosimetry; they showed an average pore size of 16.5 μm for FD, followed by PFD (8.2 μm) structures. A 27-fold decrease in average pore-size was observed for CS structure in comparison with the FD structures. Highest tensile strength (87 ± 21 MPa) was recorded for CS structures, indicating a more highly compacted network formation compared to VF (82 ± 19 MPa) and PFD (1.6 ± 0.06 MPa). Furthermore, an attempt was made to upscale the VF structures using traditional paper making approach on XMP. Improved tensile strength (73 ± 11 MPa) in machine produced structures is due to alignment of fibers towards machine direction compared to cross directional (43 ± 9 MPa) fractured structures as shown in our Scanning Electron Microscopy (SEM) analysis. Surface functionalization of MFC using enzyme (hexokinase) was performed to increase the adsorption efficiency towards ferric ions removal. All fabricated structures were further evaluated for Fe(iii) removal and it was summarized that charge densities of functional groups, produced ζ-potential and networking potential were dominating influential factors for adsorption fluctuation of ferric ions.

PORE STRUCTURE CHARACTERIZATION FOR A CONTINENTAL LACUSTRINE SHALE PARASEQUENCE BASED ON FRACTAL THEORY

Fractal dimension is an important parameter in the evaluation of tight reservoirs. For an outcrop section of the Nenjiang formation in the Songliao Basin, China, the pore structure and pore fractal characteristics of shale parasequences were investigated using fractal theory. In addition, factors causing pore structure changes were analyzed using the results of low-temperature nitrogen adsorption and scanning electron microscope (SEM) experiments. Conducive to gas migration and secondary pores development such as dissolution, results showed that nanoscale pores dominated by fracture-like morphology and consequent good internal connectivity were observed in each pore size section within the target layer. Each parasequence is characterized by a sequential upward decrease of average pore size and an upward increase of total pore volume, with an increasing number of pores from 2[Formula: see text]nm to 50[Formula: see text]nm. Pores are isolated from each other, with poor connectivity and relatively complex composition of brittle minerals and clay minerals. Main components of the brittle minerals, quartz and feldspar, occur in 20–50% and higher clay mineral content ranging from 50% to 70%. In the parasequence cycle, clay mineral gradually decreases while the brittle mineral content increases. Fractal dimension is negatively correlated with clay mineral content and positively correlated with brittle mineral (quartz and feldspar) content. The fractal dimension calculated by the imaging method and the FHH method shows an upward increasing tendency in each of the parasequence cycles. This is as a result of different phenomena, varied sediment hydrodynamic forces leading to particle size differences and increased brittle minerals resulting in microcracks, therefore, the fractal dimension of the large pores (imaging method) increases upward in the parasequence. Simultaneously, with increased content and accompanied dissolution of brittle minerals causing an increase of small pores from base to top of the parasequence, the fractal dimension of the small pores (FHH method) grows.

Cost‐effective porous ceramic tubes fabricated through a phase inversion/casting process using calcined bauxite

AbstractCost‐effective ceramic tubes based on low‐price commercial calcined bauxite for economical separation were fabricated by a new phase‐inversion casting method. The thermal shrinkage and weight loss during heating of the green tubes were characterized by dilatometric analysis and TG, respectively. Three shrinkage stages appear successively, corresponding to the viscous deformation of polymeric binder at 200‐300°C, significant combustion loss of ~5.2 wt% at 500‐620°C and sintering shrinkage over 800°C, respectively. However, due to high enough viscosity of the casting suspension that can guarantee the green tube against collapse or deformation during the phase inversion/casting process, the sintered tubes display nearly uniform microstructure instead of characteristic asymmetrical structure of the phase inversion process. The influence of sintering temperature on the pore property (including pore size and porosity) and mechanical strength was investigated. As the sintering temperature increases from 1200 to 1400°C, the porosity and average pore size decrease from 46.4% to 37.0% and from 0.98 to 0.81 μm, respectively, and the flexural strength increases from 25.8 to 65.1 MPa. The cost‐effective ceramic tube sintering at the range of 1250‐1400°C can be capable of functioning as a microfiltration membrane or an ultrafiltration membrane support.

Preparation of Compositional Gradient Polymeric Films Based on Gradient Mesh Template.

In this paper, a template-filling method was found to prepare composition gradient gelatin films by incorporating α-[3-(2,3-epoxypropoxy) propyl]-ω-butyl-polydimethylsiloxane (PDMS–E) grafted gelatin (PGG) into a gradient gelatin mesh template. The method can be used to prepare other composition gradient biopolymer films. Gradient mesh template prepared by the methacrylic anhydride cross-linked gelatin under temperature gradient field. The porosity of the template decreased from 89 to 35% which was accompanied by decrease in average pore size from 160 to 50 µm. Colloidal particles about 0.9~10 µm were formed from PGG after adding them to a mixed solvent system of 9:1 (v/v) of ethanol/water, which were filled in the mesh template under vacuum (0.06 MPa). A gradient film was obtained after drying at room temperature for 48 h. The results of scanning electron microscope-energy dispersive X-ray combined with freezing microtome and Fourier transform infrared spectroscopy suggested that the distribution of the Si element along the thickness showed a typical gradient pattern, which led to hydrophilic/hydrophobic continuous changing along the thickness of film. The water vapor permeability, thermal gravimetric analysis, differential scanning calorimetry and dynamic mechanical tensile results show that the gradient films had excellent water vapor permeability and flexibility, and hence could be used as biomimetic materials and leather finishing agents.

Improvement of microcracks resistance of porous aluminium titanate ceramic membrane support using attapulgite clay as additive

Attapulgite (ATP) clay as an important ceramic raw material appears with natural nano-rod like morphology and widely co-exists with other minor minerals. To improve the mechanical performance and to reduce the sintering temperature of aluminium titanate (AT) ceramic membrane support, porous aluminium titanate ceramic has been prepared from Al2O3-TiO2 system mixed with attapulgite clay by solid-phase reaction at relative low temperature 1300°C. The added contents of attapulgite clay were 0%, 10%, 15%, 20%, 25% and 30% in weight percent ratio, respectively. The phase composition, open porosity, strength, sintering behavior and microstructure as well as pore size distribution of porous aluminium titanate ceramic were systematically investigated. The XRD analysis suggests that the enhanced secondary phase mullite was produced when sintering temperature was above 1200°C with added attapulgite clays. The SEM images show that microcracks caused by the grain anisotropy of generated aluminium titanate were increased with the rising of sintering temperature. Both the maximum pore size and average pore size decrease with the increasing sintering temperature as the specimen was reacted with some attapulgite clay. Under the condition of 25wt% attapulgite clay addition and sintering temperature of 1300°C, the obtained porous ceramic membrane support of aluminium titanate has a open porosity of 32.41% and bending strength of 45.48MPa.

Nanoscale Pore Characteristics and Influential Factors of Niutitang Formation Shale Reservoir in Guizhou Province

Nanoscale pore characteristics are crucial in assessing the resource potential of gas shales. Although the Niutitang formation was widely deposited in the upper Yantze Platform, South China and has been recognized as a promising shale gas reservoir, there lacks substantial breakthrough in the exploitation of shale gas from the Niutitang formation. Aiming at better understanding the reservoir properties and corresponding influential factors, 14 core samples from the Lower Cambrian Niutitang formation locating in the central Guizhou province were investigated in the current study to characterize the nanoscale pore system in the shale. Organic geochemical analyses (i.e., total organic carbon content and thermal maturity), X-ray diffraction, low pressure nitrogen adsorption, and field emission scanning electron microscopy were employed to obtain complementary information of the pore system. Measured TOC in this study is generally > 1.50% and averages 3.35%. All of the samples are in the over-maturity stage with R-o ranging from 2.39% to 3.29%. X-ray diffraction shows that quartz, clay minerals and plagioclase are the dominant minerals. Nitrogen adsorption results indicate that all of samples show type IIb nitrogen adsorption isotherms with type H3 hysteresis loops, which imply the coexistence of micropores, mesopores and macropores in the shale. The mesopores account for 60-70% of total pore volume, and are likely contributed by clay minerals and quartz. Organic matter appears to be the major contributor of the micropores and specific surface area, and is closely linked to the rapid decrease of average pore size with increasing burial depth. The field emission scanning electron microscopy reveals abundant organic matter pores in the middle-upper Niutitang formation, but lesser or smaller in the bottom of Niutitang formation. The lower Niutitang formation seems to develop substantial amounts of organic-clay aggregates, which preferentially lie parallel to the shale bedding and contain lots of nanoscale pores. The perpendicular variation of pore structure features is explained with multiple mechanisms, including thermal maturation of organic matter, compaction by strata pressure, dissipation of shale gas, etc. The results of our study have emphasized the interesting and complex features of the nanoscale pore structures in the gas shales, which may facilitate future assessment and exploitation of shale gas resources.

La, Mn and Zn promoted microporous iron catalysts with high productivity and stability for Fischer–Tropsch synthesis

Fischer–Tropsch synthesis is studied over precipitated Fe catalysts promoted with Mn, Zn and La metals. The results showed that there was a large increase in surface area and pore volume, and a sharp decrease in average pore size upon the addition of promoters. Catalyst productivity and rate of syngas converted as well as hydrocarbon yield increased with addition of promoters to Fe structure during precipitation step. Addition of metal promoters led catalyst samples of microporous structures with relatively high surface areas. This effect probably yielded catalysts with enhanced long-term activity and stability. Samples containing 10 % Zn and 5 % Mn exhibited the highest catalytic activity and stability. Increasing the loading of Zn from 5 to 10 wt% led to a noteworthy increase on yield and productivity as well as rate of syngas converted. The highest productivity was obtained for the sample containing 10 % Zn, highest yield was attained over the sample containing 5 % Mn. The results indicate that the selectivity to C12–C18 range was more pronounced for the catalyst promoted with Mn metal whereas α-olefins and higher molecular weight products were increased with the addition of 5 % Zn over Fe based catalysts. The decrease in temperature from 523 to 493 K resulted in an increase in heavy hydrocarbons and a significant decrease in gaseous and light hydrocarbons for Fe4Si5Mn catalyst.

Physical and mass transfer properties of electrospun ɛ-polycaprolactone nanofiber membranes

Determination of material properties and functions is a crucial step toward optimization of fabrication methods as well as the development of electrospun nanofibers for use in, e.g. food engineering applications. This work focused in evaluating physical and mass transfer properties of simple poly ɛ-caprolactone nanofibers (PCL membrane), and poly ɛ-caprolactone nanofibers with encapsulated trypsin (E-PCL membrane), in view of their future use in a catalytic filter reactor.PCL membranes registered high hydrophobicity values, while E-PCL membranes revealed stronger mechanical properties and an increase of mass due to water incorporation. A decrease of average pore size in the range of 30–40% was observed for E-PCL membranes and an average pore diameter of 1/3 of the size was registered when compared to the PCL membrane; this difference was shown to be significant enough to influence the transport of larger molecules (e.g. bovine serum albumin).Release experiments of active compounds (lysozyme, bovine serum albumin and lactoferrin) were successfully described by a model which accounts for both Fick and case II transport – the linear superimposition model. Results show that the transport mechanism is influenced by the type of active compound and by membranes’ physical properties.