Pore Size Of Channels Research Articles

Results of capillary studies digital processing and interpretation with the aim of a pore channel size distribution function constructing

Pore channels distribution in reservoir by size largely determines such filtration parameters as absolute and phase permeability, as well as the residual oil saturation of the productive reservoir. This paper presents a technique for capillary research data digital processing in order to obtain a function graph of reservoir pore channels by size distribution. In this case, a generalized mathematical model of capillary pressure curves is used. The generalized model makes it possible to increase the accuracy of capillary curves approximation in the medium and small pore channels area. In this regard, the proposed digital processing technique makes it possible to increase the accuracy and efficiency of constructing the pore channel size distribution function. Keywords: pore channels; distribution density; permeability; oil saturation; digital processing technique.

PdIr nanoparticles on NH2-functionalized dendritic mesoporous silica nanospheres for efficient dehydrogenation of formic acid

Developing highly efficient solid catalysts for formic acid (HCOOH, FA) dehydrogenation is essential to utilize FA as a hydrogen (H2) carrier. In this work, ultrafine bimetallic PdIr nanoparticles (NPs) supported on the amine-functionalized dendritic mesoporous silica nanospheres (PdIr/DMSNs-NH2) have been successfully synthesized by the simple surface functionalization and co-reduction method. The optimized Pd4Ir1/DMSNs-NH2 (Pd/Ir molar ratio = 4:1) catalyst displayed the remarkable catalytic performance with 100 % H2 selectivity of the FA dehydrogenation, and the initial turnover frequency (TOF) could achieve 1333 h−1 with the additive of sodium formate (SF) at 298 K, which is comparable to the most effective mesoporous silica supported Pd-containing solid catalysts. The activation energy (Ea) for the FA dehydrogenation of Pd4Ir1/DMSNs-NH2 catalyst in the FA-SF mixture is 39.7 KJ/mol, lower than most reported catalysts. Furthermore, the optimized catalyst maintained 100 % H2 selectivity even after five runs, only with a negligible decrease in the activity, displaying the excellent stability of the catalyst. The superior catalytic performance could be attributed to the synergistic effect of open dendritic pore channel, high dispersion and ultrafine size of PdIr NPs as the active sites on DMSNs-NH2, and regulated electronic effects of Pd and Ir. More importantly, introducing –NH2 groups to the DMSNs could facilitate the O–H bond dissociation of FA and improve the FA dehydrogenation activity under mild conditions. This work will significantly promote FA as a hydrogen carrier on fuel cells.

Microstructure and permeability of porous YSZ ceramics with aligned and gradient pore channels fabricated by freeze casting

Porous yttria-stabilized zirconia (YSZ) ceramics with aligned and gradient pore channels were fabricated by the unidirectional freezing of aqueous suspensions with distinct solid loadings under different sintering temperatures. The results indicate that the microstructure and response properties could be tailored by adjusting the solid loading and sintering temperature. The pore channel size increased with the increase of solid loading or the decrease of sintering temperature, regardless of microstructure changes in an individual sample. With increasing the solid loading and sintering temperature, the compressive strength (7.18–30.76 MPa) increased owing to the lower porosity of individual samples. The fabricated samples had increasing Darcian and non-Darcian constants along the freezing direction due to the enhanced pore size and open porosity. The Darcian and non-Darcian constants in this paper were in the range of 7.06 × 10−13 to 5.92 × 10−12 m2 and 1.66 × 10−7 to 8.83 × 10−7 m, respectively. These results are of practical value for the fabrication and optimization of porous ceramics in the applications of filters and membrane supports.

Construction of novel super microporous silica adsorbents using pluronic triblock copolymer as template towards desulfurization from fuel

As an efficient fuel purification technique, adsorption desulphurization has attracted wide attention. Silicon oxide has been verified as a promising candidate for adsorption desulfurization reagent due to the advantages of stable structure, inexpensiveness and accessibility. However, its adsorption desulfurization performance is always weakened by the limited pore channel size leading to pore diffusion resistance over the traditional microporous silicon oxide, and it suffers from the poor shape selectivity of mesoporous silicon oxide as well. In this work, we successfully prepared a novel super microporous silica material (SMS) with a unique bimodal micro-mesoporous pore size distribution mainly around 1.2 nm, 1.6 nm and 1.8 ∼ 3.5 nm, using a pluronic triblock copolymer with approximately an average molecular weight of 3858 as template by hydrothermal synthesis. The SMS possessed the characteristics of Ia3d cubic phase and super microporous as well as mesoporous silica structure, according to the X-ray diffraction characterization as well as nitrogen adsorption isotherms. The SMS could effectively reduce the diffusion resistance and exhibit improved shape selectivity compared to microporous or mesoporous silicon oxide, respectively, by virtue of its bimodal micro-mesoporous pore size distribution. Under an optimized crystallization temperature of 100 °C for 24 h, the as-synthesized SMS displayed a notable desulfurization performance with a breakthrough capacity of 0.122 mmol S/g benzothiophene, which was significantly superior to that of traditional mesoporous silica KIT-6 (0.04 mmol S/g). Furthermore, the desulfurization performance of SMS adsorbent was not significantly reduced after three cycles of regeneration. The SMS exhibited high desulfurization capacity, easy regeneration and satisfactory regeneration performance, and it could be applied in adsorptive desulfurization technology.

Study of the structure and development of oil deposits in carbonate reservoirs using field data and X-ray microtomography

At present, a large number of scientific works devoted to the study of the features of the geological structure and the development of oil deposits in complex carbonate reservoirs are based on the use of any one research method. This article shows the advantages of the integrated use of modern methods of core research, including X-ray microtomography and electron microscopy, as well as data from hydrodynamic and field studies of wells. The advantage of the approach used is the ability to study the deposit at three levels: core-well-development object, it is reasonable to transfer micro-survey data to the regularities of the implementation of technological processes of oil production. The objects of research in this article are the Famennian oil deposits of two neighboring fields, which, at first glance, are analogues in terms of the similarity of the enlarged geological and physical characteristics. Comprehensive studies of core samples from these deposits made it possible to establish differences both in the mineral composition of rocks and in the structure of their void space, especially in the size and distribution of pore channels. So, with approximately equal porosity for one of the deposits, the presence of two types of voids and a twofold prevalence of the size of the largest of them were established. According to the complex of laboratory methods for studying the core, the reservoir is classified as a porous type (no cracks were found). The performed interpretation of the hydrodynamic studies confirmed this fact, made it possible to establish the presence of a dependence of the reservoir permeability on the formation pressure (deformation of the void space of the reservoir), and also to build the corresponding individual dependence for each well. Comparison of the equations approximating the dependence data showed a more pronounced deformation of the reservoir, which is characterized by the presence of large pores and caverns. That is, a complex of laboratory and hydrodynamic studies made it possible to establish the probability of deformation of the void space of a carbonate reservoir even in the absence of cracks in it. In turn, the reservoir deformation is singled out as the most probable cause explaining the different rates of decline in well flow rates of the fields under consideration.

Metal–Organic Frameworks Nanoarchitectures Boost Catalytic Activity for the Construction of Sensitive Immunosensor

AbstractBenefiting from the distinct structural features, metal‐organic frameworks (MOFs) open new significant opportunities for biomacromolecule encapsulation to design biofunctional composites, whereas their biological activity and utilization efficiency remain challenging for the construction of advanced immunosensor. Herein, biomacromolecules are spatially encapsulated integration on the cavity of peptide‐mediated MOFs with controllable nanoarchitectures, which amplifies the immunosensor signals via boosting bioactivity and utilization efficiency. Notably, the morphological evolution of MOFs composite including dodecahedrons, nanostars and flower‐shaped nanostructures is achieved by introducing peptide surface modifier to trigger the coordination defects procedure. Nanostars are evidenced with the enhanced catalytic activity of biomacromolecules, which amplifies the recognition signal via regulating the pore channel and particle size of biomacromolecules@MOFs composite, shortening the diffusion path of substrate molecules and promoting the interfacial contact. As proof‐of‐principle, imidacloprid is chosen as a model target to demonstrate the superiority of biomacromolecules@MOFs‐based immunosensor. Combining the enhanced activity of biomacromolecules with size tunability of biomacromolecules@MOFs composite, 160‐fold improvement in the sensitivity is obtained in comparison with the conventional enzyme‐based immunoassay, paving the way for the employment of controllable nanostructures for high‐sensitive biosensors.

Formation of Nanowires of Various Types in the Process of Galvanic Deposition of Iron Group Metals into the Pores of a Track Membrane.

The processes of formation of one-dimensional nanostructures by the method of matrix synthesis was studied in this work. Nanowires (NWs) from magnetic metals of iron-group and copper (3-d metals) were synthesized in the pores of matrix-track membranes by galvanic deposition. NWs with both homogeneous elemental distribution (alloys) and with periodically alternating parts with different composition (layers) were obtained in matrices with different pore diameters and under different parameters of the galvanic process. The transport of ions, which determined the growth of wires, in pores of different sizes was analyzed. The influence of the size of pore channels on the features of NWs growth, the correlation between the elemental composition of the NWs and the growth electrolyte, as well as the influence of the growth conditions (voltage and pore diameter) were investigated. Approaches to formation of thin layers in layered NWs were studied. This included the choice of methods for controlling the pulse duration, slowing down the growth rate by the dilution of the solution, the use of additives and the work with reference electrode. The study of NWs was carried out using visualization and analysis of their structure using transmission and scanning electron microscopy, electron diffraction, energy dispersive analysis, and elemental mapping. For the studied types of samples, a relationship was established between the growth conditions and the structure. This data raises the possibility of varying the magnetic properties of NWs.

Filtering pore chanels distribution density in Western Siberia

It is well known that information on filter channels distribution density can be obtained based on the data of core samples capillary studies in laboratory conditions. The curve of the fractional participation of pore channels in filtration, as a rule, is obtained by numerical processing of the capillary studies results. In this study, using a generalized mathematical model of capillary curves, an analytical solution is obtained for filtration channels distribution density by size in the conditions of Western Siberia reservoirs. The work shows that the main share in the filtration is taken by pore channels, the sizes of which are close to the maximum value. The density function of the filtering channels is mainly determined by the maximum radius and heterogeneity of the pore channel size distribution. Keywords: capillary pressure curve; generalized model; distribution density; filtering channels.

Research of the process of obtaining capillary-porous materials from metal powders for heat pipes

Heat pipes are designed to effective removing heat from heating elements and reducing the temperature of various devices. Heat pipes with capillary porous structures are designed to operate under conditions of unfavorable gravity forces. Their main advantages are their high heat transfer capacity, as well as the ability to retain the coolant in a capillary-porous structure under dynamic power loads. The purpose of this work is to study the process of obtaining capillary-porous materials from metal powders for heat pipes with increased efficiency of using the vibration molding method. The article substantiates the relevance of creating heat pipes from metal powders. The information about the influence of the contact angle, surface tension and capillary pressure on the heat transfer capacity of a heat pipe is provided. It is shown that for the efficient operation of the heat pipe it is necessary to create such a capillary structure of the porous material, which could simultaneously provide a high speed of movement of the coolant and its rise to a given height. The above requirements can be satisfied by creating a capillary structure using powder metallurgy methods by optimizing the distribution of pore sizes. In this case, the most promising method seems to be the method of molding when applying a vibration to a mold with a powder. It is possible to obtain the required pore distribution in this way by choosing the correct particle size, shape and vibration parameters. This makes it possible to ensure the packing of particles in size, which affects their packing density, pore size, tortuosity and length of pore channels. The distribution of the maximum pore sizes over the thickness of the samples obtained from powders of various granulometric composition with the use of vibration has been investigated. As a result, a process was developed for obtaining capillary structures by the method of vibration molding of metal powders, depending on the size of the powder particles, the amplitude and frequency of vibration. It is shown that this method can provide a given pore distribution of the capillary structure for heat pipes, which makes it possible to increase their heat transfer capacity.

Preparation of AlN micro-honeycombs with high permeability via freeze-casting

Highly permeable AlN micro-honeycomb (AlN-H) ceramics with unidirectional macropore channels and porous struts were fabricated via tertiary butyl alcohol (TBA)-based freeze-casting. The effect of the AlN solid loading of the freezing slurries on the microstructure, open porosity, N2 gas permeability, and compressive strength of the as-prepared AlN-Hs were systematically investigated. The results showed that the honeycomb structure and open porosity of the AlN-Hs can be adjusted by altering solid loading. With the increase in solid loading from 10 vol% to 30 vol%, the approximate pore channel size of the AlN-Hs decreased from 50.1 μm to 15.6 μm, strut thickness increased from 8.2 μm to 16.6 μm approximately, and the corresponding open porosity decreased from 87.6–56.6%. The as-fabricated AlN-H with an open porosity of 64.9% possessed high N2 gas permeability and essential compressive strength and can be used as a catalyst support or filter in industries.

Laser surface modification of porous yttria stabilized zirconia against CMAS degradation

Here, we present a new combined freeze-casting and laser processing method for the design of yttria-stabilized zirconia (YSZ) based thermal-barrier coatings. YSZ ceramics with unidirectionally-aligned pore channels were created using the freeze-casting method. After sintering, top view and cross-sectional scanning electron microscopy (SEM) revealed the structural features of the preform, which exhibits a 74 ± 2% volume fraction of porosity and an average pore channel size of 30 ± 3 μm. The measured thermal conductivity of this porous structure was 0.27 ± 0.02 W/(m K), which is eight times lower than that of reported values for dense YSZ. Though high porosity is beneficial both from a structural and thermal response perspective, the open porosity could potentially be an issue from an application stand-point when evaluating the resistance of materials to calcium–magnesium–aluminum–silicon oxide (CMAS) attack. CMAS attack, which can originate from deposits of molten sand, ash, and dust, is one of the major causes of thermal barrier coating failure. Therefore, the surface of the porous samples was modified using a laser process to create a barrier to CMAS infiltration. SEM micrographs aided in determining the optimum laser parameters required to fully seal the surface using a laser treatment. The performance of the original porous and surface-modified YSZ was compared by conducting CMAS infiltration studies. Laser modification was shown to be a viable technique to significantly reduce CMAS infiltration in porous thermal barrier coatings.

Hydrogenation of Alkylanthraquinone Over Pore-Expanded and Channel-Shortened Pd/SBA-15

SBA-15 silica was synthesized by adding normal paraffin and alkyl benzene as swelling agents and using a low-temperature gelation procedure. Pd was then impregnated on SBA-15, yielding a catalyst. Characterizations of the catalyst by X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, transmission electron micrographs, X-ray photoelectron spectroscopy, in situ FTIR, and a hydrogenation test of 2-ethyl-anthraquinone reveal that the addition of C6‒C9 normal paraffin and 1,3,5-triisopropylbenzene could enlarge the pore diameter without a significant loss of ordered structure. Moreover, the length of SBA-15 pore channels decreased significantly. However, the sizes of Pd particles increase as the pore diameter is enlarged. The largest pore size (13.6 nm) and short length of pore channels (ca. 0.35 μm) are achieved by adding n-hexane. As a result, this catalyst exhibits the highest hydrogenation activity with an approximately 100% improvement, compared with a conventionally synthesized catalyst in the absence of a swelling agent.

Preparation of cellulosic air filters with controllable pore structures via organic solvent-based freeze casting: The key role of fiber dispersion and pore size

Green and biodegradable cellulose filters with controlled designer pore structures were prepared using organic solvent-based freeze casting. In this paper, the relationship between the different freeze media, including ethanol, isopropanol, and tertiary-butyl alcohol, and the microstructure of the porous filters was investigated. The results of the pore size distribution indicated that the pore channel size decreased remarkably when organic solvents were used as the freezing media. Moreover, the filters showed high filtration efficiencies, up to 99.70% and 99.66% for 0.5 µm and 0.3 µm particles, respectively, under a pressure drop of 180 Pa and at 32 L·min-1 flow rate. The fabrication of cellulosic filters would not only make it a promising candidate for capturing fine particulate matter, but also provide a versatile approach to regulate and design a porous structure for materials applied in various fields.

Characterization of Microscopic Pore Structures of Rock Salt through Mercury Injection and Nitrogen Absorption Tests

Microscopic pore structure of rock salt plays a dominant role in its permeability. In this paper, microscopic pore structure of a set of rock salt samples collected from Yunying salt mine of Hubei province in China is investigated by high pressure mercury injection, rate-controlled mercury penetration, and nitrogen absorption tests. The pore size distribution is further evaluated based on fractal analysis. The results show that pore size of rock salt varies from 0.01 to 300 μm with major concentration of pore size smaller than 1.00 μm. The pore’s radiuses are mainly distributed within a range between 15 and 50 nm. The research further reveals that the pore channel size of rock salt is randomly distributed, but the distribution of pore throat radius fits very well with fractal law. By analysis of permeability, it is found that the maximum and medium radius of the pore throat have significant impacts on permeability. Porosity is not apparently related to the permeability of rock salt. The higher the fractal dimension is, the higher the impacts on permeability of the small throat are detected and the lower the influence on permeability of the big throat is exhibited. It indicates that the small throat determines majorly the permeability of rock salt. The findings obtained from this study provide an insight into understanding the characteristics of microscopic pore structure of rock salt.

Self-Assembly Synthesis of Large-Pore Fe/N-Codoped Ordered Mesoporous Carbon for Supercapacitor Electrode Materials

A slightly optimized method of evaporation induced self-assembly (EISA) has been used to synthesize large-pore Fe/N-codoped ordered mesoporous carbon directly by using phenolic resin as the carbon source and commercial triblock copolymer F127 as the soft template, as well as pyrrole and urea as the nitrogen source. The large-pore mesostructure was obtained by introducing FeCl3 for inducing pyrrole polymerization under acidic conditions during the self-assembly process. Meanwhile, the pore size can be adjusted through altering the molar ratio of FeCl3 to pyrrole monomer. The prepared materials have a particularly tortuous pore channel and large-pore size distributions (4 nm to18 nm), high specific surface area (288 to 496 m2·g−1) and pore volume (0.40 to 0.62 cm3·g−1). Electrochemical tests demonstrate that all samples possess excellent performance of electric double-layer capacitors and rate capability. Notably, the sample S0.5 with a pore size of 11 nm can obtain a specific capacitance of 257 F·g−1 at a current density of 1 A·g−1 and the capacitance retention of 92% after 1000 cycles at 10 A·g−1. It can be concluded that these advantages have promise to provide the new thought for large-pore mesoporous carbon materials in the application of supercapacitor electrode materials.

Shape selectivity of beta and MCM-49 zeolites in liquid-phase alkylation of benzene with ethylene

NH3, pyridine and 2,4,6-trimethyl-pyridine were selected as the base probes to characterize the different pore acidity of H-beta and H-MCM-49 zeolites, revealing the essence in their catalytic performance from the view of shape selectivity in different pore systems. Based on the size of base probes, reactants, product, transition states and pore channels, the difference in catalytic performance over H-beta and H-MCM-49 was investigated. Easy diffusion of reactants into and long diffusion distance for ethylbenzene escaping out of confined space within beta are the main reason for superior activity and poorer ethylbenzene (EB) selectivity. As for H-MCM-49, acid sites located in 10 MR channels contributed little to the formation of EB due to transition state selectivity; Acid sites located in 12 MR cups on the outer surface with little restriction on the diffusion of reactant/product toward/from the active centers were the major active centers for EB formation, which could be detected by 2,4,6-trimethyl-pyridine; There was diffusion limitation on reactant/product in 12 MR supercages through 10 MR windows to influence activity/selectivity. The enhancement in activity and selectivity in liquid-phase alkylation of benzene with ethylene over MWW zeolites should be mainly focused on transforming confined 12 MR supercages into 12 MR cups with improved openness.

Fabrication of lamellar porous alumina with axisymmetric structure by directional solidification with applied electric and magnetic fields

A novel directional solidification method was used to fabricate lamellar porous alumina with an axisymmetrical structure by combining multiple cold sources, electrostatic field, and magnetic field during the freezing of aqueous alumina slurries. Multiple cold sources with mutually perpendicular directions formed by the bottom and parallel sides of rectangular copper molds induced a specific growth direction for ice crystals. The pore channels of porous ceramic are arranged parallel to the direction of electric field lines, and the axisymmetrical structure was obtained after applying the electrostatic field. The applied magnetic field can reduce pore channel size; however, the field has no effect on pore channel direction and distribution, and leads to cracking in the central region of porous ceramics. The compressive strength along the electrostatic field direction is higher than that achieved by conventional freeze casting.

Combustion synthesis of porous oxynitride materials under conditions of forced filtration of reacting gas

Combustion synthesis is a promising technique for producing the oxynitride ceramics, which represent a new class of materials with high resistance to high temperatures and to intensive wear. The different experimental ways of control of combustion parameters were considered, such as sample porosity, porosity structure of samples, different experimental configurations (coflowing and opposite flow systems), and pressure. Kinetic features of nitrogenation of reacting samples (aluminium, silicon oxide and sialon powders) were analyzed at different conditions. Forced nitrogen filtration through porous sample substantially improved the process of combustion synthesis (yield with higher nitrogen content, porous structure). The application of coflowing configuration intensifies the combustion synthesis and provides the re-heating process by convective heat transfer from combustion products to the initial mixture. It was demonstrated that this process leads to super-adiabatic temperature rise in the combustion zone. Coflowing configuration allow one to synthesize porous sialon with the conversion ratio up to 0.995 with combustion rate 0.8mm/s and maximum combustion temperature about 1900°C. The parameters of porous samples were varied in a wide range: sample porosity: 40–75%, the average sizes of the skeleton elements – from 240μm to 3.5mm; average pore-channel size 10–390µm; percentage of closed porosity 16–30%.

Colloido-chemical characteristics of nanoporous glasses with different compositions in solutions of simple and organic electrolytes. 1. Structural and transport characteristics of membranes

The regularities of variations in the structural (bulk porosity, structural resistance coefficient, and average pore radius) and transport (specific electrical conductivity and ion transport numbers) characteristics of nanoporous glass membranes with different compositions have been studied as depending on their preparation conditions and the type of electrolyte (sodium, potassium, ammonium, tetramethylammonium, and tetraethylammonium chlorides). An additional alkaline treatment of the porous glasses, which increases the average pore radius and modifies the morphology of pore channels, leads to variations in the electrotransport characteristics of the glasses. In solutions containing inorganic counterions, the dependences of the transport characteristics of the porous glasses on the solution concentration and pore size have a classic character. The high specificity of tetraalkylammonium ions in relation to the surface gives rise to a region of negative values of the specific surface conductivity and complex dependences of efficiency coefficients and transport numbers on electrolyte concentration and pore channel size. The duration of the thermal treatment of initial sodium-borosilicate glass containing small amounts of phosphorus oxide and fluoride ions, as well as the conditions of its leaching, has almost no effect on the properties of the membranes in tetraethylammonium chloride solutions.

Methods for a permanent binding of functionalized micro-particle on polyester fabric for the improvement of the barrier effect

Polyethylene terephthalate multifilament fabrics used as filtration and operating room textiles possess through-thickness pore channels at the yarn intersections (meso-pores). These pore channels pose a risk for the penetration of contaminated fluids and particles. The size of pore channels may be reduced by high-density weaving. However, this leads to reduced drapability and thus to degraded application properties of the fabric. To satisfy the requirements without impeding the physiological properties of the textile, fluid- and particle-tight fabrics are developed. This was realized by partial immobilization of functionalized micro particles into the meso-pores. A reduction of the pore size without complete pore-closure is achieved by establishing a net-like particle structure in the meso-pores. To match the requirements of intensive use, permanent particle-bonding to the fiber surface is necessary. This can be achieved by suitable polyethylene terephthalate fabric surface-modification, dependent on the particle functionalization. The investigations have shown that functionalized particles establish a very good inter particle bonding as well as to the fiber surface. An increased permanent bonding can be realized by a modification of the fabric surface which is tuned to the functionalization of the particle.