Pore Diameter Distribution Research Articles

Amino acids functionalized graphene oxide for enhanced hydrophilicity and antifouling property of poly(vinylidene fluoride) membranes

Herein, functionalized graphene oxide (GO) was prepared by the covalent functionalization with amino acids (lysine, glycine, glutamic acid and tyrosine) in this study. Zeta potential results demonstrated that covalent functionalization of GO with amino acids was favourable for their homogeneous dispersion in water and organic solvents. Based on the higher absolute value of zeta potential and the better dipersion stability of GO-lysine, the PVDF/GO-lysine hybrid membranes were then prepared via the phase inversion induced by immersion precipitation technique. SEM images showed a better pore diameter and porosity distribution on the PVDF/GO-lysine membrane surface. The zeta potential absolute value of the PVDF/GO-lysine membrane surface was higher than that of the virgin PVDF membrane. Furthermore, the PVDF/GO-lysine membranes surface exhibited good hydrophilicity. The water flux of PVDF/GO-lysine membranes can reach two times of that of the virgin PVDF membrane. And the BSA adsorbed amount on PVDF/GO-lysine surface was decreased to 0.82 mg/cm2 for PVDF/GO-lysine-8% membrane. Filtration experiment results indicated that the fouling resistance was significantly improved for the PVDF/GO-lysine membranes. As a result, lysine functionalized GO will provide a promising method to fabricate graphene oxide based hybrid membranes with effective antifouling property and hydrophilicity.

A new graphene/geopolymer nanocomposite for degradation of dye wastewater

ABSTRACTA novel graphene/geopolymer nanocomposite was firstly synthesized by using two-dimension graphene (GR) and alkali-activated granulated blast furnace slag-based geopolymer (ASG), and used to degrade simulation dye effluents. Diffuse reflectance UV–Vis spectrum indicated that the maximum absorption wavelength of the nanocomposite (GR/ASG) is red-shift to the visible region. The pore diameter distribution results of the GR/ASG1 sample showed that at least 89.59% of pore volume centralized on the region of 2–50 nm. The photocatalytic degradation efficiencies of samples for methyl violet dye is in the order of GR/ASG1 > GR/ASG2 > ASG under the irradiation of UV. The GR/ASG1 photocatalyst exhibited the highest degradation efficiency and approached to 91.16% for 110 min. The photocatalytic degradation reaction belongs to the second-order reaction kinetics.

Experimental studies on an indigenous coconut shell based activated carbon suitable for natural gas storage

Experimental studies are carried out to characterize an indigenous, coconut shell based, activated carbon suitable for storage of natural gas. Properties such as BET surface area, micropore volume, average pore diameter and pore size distribution are obtained by using suitable instruments and techniques. An experimental setup is developed to estimate the equilibrium methane adsorption capacity and adsorption/desorption kinetics. The experimental isothermal uptake data is used to fit four different isotherm models. Using the constants obtained for the D–A isotherm model the variation of heat of adsorption and adsorbed phase specific heat with equilibrium pressure and temperature are obtained. Similarly Henry’s Law coefficients, important at low pressure and low uptake regime are also obtained. Finally using the kinetic data and a linear driving force model, constants in the kinetic equation are obtained. Results show that the indigenous material used in this study offers reasonably high natural gas storage capacity and fast kinetics and is suitable for adsorbed natural gas (ANG) applications. It is expected that this study will be useful in the design and development of ANG systems based on this indigenous material.

Influence of composition on the mesoporous structure of the silica gel prepared by sol–gel method

The effect of composition on of the mesoporous structure of the silica gels prepared by sol–gel technique has been investigated. Two types of alkoxides were used simultaneously: tetraethoxysilane was used as the base alkoxide, the 3-glycidyloxypropyltrimethoxysilane, vinyltriethoxysilane, methyltrimethoxysilane, N-(3-(trimethoxysilyl)propyl)-ethylenediamine, octyltriethoxysilane were selected as the second silicate source. Experimental data were analyzed using n-way analyze of variance (linear model). The results showed that the structure and amount of the second alkoxide in the sol composition have strong influence on the pore characteristics of material. Specifically, longer and more branched chain of the second alkoxide results in larger specific surface area and wider pore diameter distribution. The chains of the second alkoxide behave as a template during gelation step, and they are fully removed from silica gel matrix during the calcination step. The samples with the highest specific surface area and total pore volume were obtained based on the mixture of octyltriethoxysilane with tetraethoxysilane.

Influence of the Method of Aqueous Synthesis and the Nature of the Silicon Precursor on the Physicochemical Properties of Porous Alumina

AbstractThe aqueous sol‐gel synthesis of γ‐Al2O3 modified with different silicon precursors {trimethoxysilane, triethoxysilane and N‐[3‐(trimethoxysilyl)propyl]ethylene diamine} has been investigated. Two parameters have been studied: the silicon addition step and the type of silicon alkoxide. A first observation was that adding a silicon alkoxide either before or just after the precipitation step influences both the crystallinity and structure, whereas adding the alkoxide after a long agitation time only slightly modifies the support properties. It was also highlighted that due to their higher reactivity, silicon precursors with methoxy groups interact more strongly with the bulk alumina than the silicon precursors with ethoxy groups. This difference of Si location in the alumina structure permitted not only their resistance toward phase transition to be increased at high temperature, but also to stabilize them more efficiently against sintering under normal and steam conditions. Among the different silicon alkoxides tested, samples prepared with N‐[3‐(trimethoxysilyl)propyl]ethylene diamine showed very unusual properties. The alumina supports modified with this precursor showed grain‐shaped nanocrystallites, whereas all other samples were platelet‐like. As a result, this sample presented a very narrow pore diameter distribution of around 5 nm and a remarkably high specific surface area (530 m2/g).

Effects of Precipitation and Drying Processes on the Synthesis of Silica Materials with a Large-Pore-Volume and Narrow-Pore-Diameter Distribution

In this paper, a novel process using the combination of a microreactor and a stirred-tank reactor for the controlled preparation of silica materials with a large-pore-volume and narrow-pore-diameter distribution was presented. At the precipitation stage, the gelation time was controlled to within 50 ms by improving the mixing performance in the microreactor. After further mixing and acidizing in a stirred-tank reactor, silica with a pore volume of 1.96 mL/g and a specific surface area of 476.1 m2/g was prepared. The primary particle size was 10 nm, and the variance of the logarithmic pore diameter was approximately 0.20, which indicated that the pore-diameter distribution was narrow and uniform particles were in favor of accumulating uniform pores. At the drying stage, with the addition of poly(vinyl alcohol) to a silica slurry, the process conditions were optimized, and silica with a larger pore volume of 2.13 mL/g was prepared.

Hierarchical porous carbon nanofibers as binder-free electrode for high-performance supercapacitor

1D hierarchical porous carbon nanofibers (HPCNFs) are prepared via electrospinning ternary PAN/N, N’-dimethylformamide (DMF)/tetrahydrofurar (THF) and using commercially available nano-CaCO3 as template. In the process of carbonization, nano-CaCO3 template decomposes and releases CO2 to form micropores and mesopores. Macropores are generated by removing the CaO nanoparticles using acid subsequently. The hierarchical pores are fairly well distributed because the nano-CaCO3 particles are highly dispersed in the fiber due to the better wettability in binary solvent. The obtained HPCNFs attain high specific surface area without physical and chemical activation. The HPCNF mats, possessing free-standing architecture, are used as binder-free electrodes for supercapacitor. Because of high specific surface area, rational pore diameter distribution and binder-free characterization of electrodes, the HPCNFs display a high capacitance of 251Fg−1at a current density of 0.5Ag−1 as well as excellent rate capability and outstanding cycling stability (over 88% capacitance retention after 5000 cycles at the current density of 1Ag−1). These results demonstrate that the binary solvent method is effective to achieve high-performance electrode materials and it has a promising prospect on applications of energy storages.

The closed pores of tectonically deformed coal studied by small-angle X-ray scattering and liquid nitrogen adsorption

To study the variation in the characteristics of closed pores in coal under tectonic deformation, three coal samples are selected that differ only slightly in metamorphic degree but differ sharply in deformation degree, with vitrinite reflectance range from 0.88% to 0.96% and deformation degrees corresponding to weak brittle, strong brittle and strong ductile deformations. The experimental methods used are small-angle X-ray scattering and liquid nitrogen adsorption, and the pore diameters obtained by combining the two methods are within the mesopore (2–50 nm) size range. The deformation of coal narrows the distribution of pore diameters. Changes in pore shape are described according to fractal theory: the pore fractal dimension is larger in coal with a greater pore size, and tectonic movement promotes irregularity and fracturing of the original pores. The specific surface area of pores is calculated in this paper. We conclude that the proportion of closed pore specific surface area reaches the peak with the increase of the deformation degree, and then falls gradually. Pore diameters greater than 3.2 nm and less than 3.2 nm correspond to the two parts in the liquid nitrogen adsorption data, with the fractal dimension of the former being larger than that of the latter. The results also show that the closed pore volume increases but the proportion of the total pore decreases with increasing deformation degrees.

毛管径分布を考慮したループヒートパイプの熱輸送特性

毛管径分布を考慮したループヒートパイプの熱輸送特性

压汞法与气体吸附法联用分析沈352井致密储层岩石孔隙结构

油气储层孔隙直径分布研究的主要技术手段有压汞法、气体吸附法等。压汞法常用于测试连通的中孔和大孔的孔隙结构。氮气吸附法侧重于表征微孔和中孔的孔隙结构。仅靠一种方法不能给出孔结构的所有信息。因此，压汞法和气体吸附法相结合分析全孔隙结构特征尤为重要。本文将两种测试方法联用，分析沈352井致密储层岩石(油页岩、泥质泥晶云岩、云质泥岩)全孔隙结构的孔径分布特征，认为：油页岩中孔隙直径小于100 nm的占70%左右；孔隙直径呈现“三个峰”，第一个主峰为5~30 nm，次峰30~200 nm，第三个峰1000~3000 nm。泥质泥晶云岩中孔隙直径小于100 nm的占75%左右；孔隙直径略现“二个峰”，第一个主峰为2~30 nm，次峰50~100 nm。含云泥岩或云质泥岩中孔隙直径小于100 nm的占90%以上；孔隙直径以小于15 nm为主。 Mercury injection and gas absorption analytical methods are the main technical means of pore diameter distribution diagram of Petroleum Reservoir. Mercury injection method constantly is used for determination of connected middle pore and macropore, and gas absorption method is used for determination of Microporous and middle pore. Based on combination of mercury injection and gas absorption analytical methods, the complete pore diameter distribution diagram of tight reservoir rock can be obtained. By the use of the combination of two methods in tight reservoir rock of the well of shen352, the author makes a conclusion: Pore diameter which is less than 100 nm of oil shale is about 70%; it has “three peaks” at 5 - 30 nm, 30 - 200 nm and 1000 - 3000 nm. Pore diameter which is less than 100 nm of pelitic micrite dolomite is about 75%; it slightly presents “two peaks” at 2 - 30 nm, 50 - 100 nm. Pore diameter which is less than 100 nm of dolomitic mudstone is more than 90%; the main range of pore diameter of this rock is less than 15 nm.

Syntheses, characterization and adsorption properties for Pb2+ of silica-gel functionalized by dendrimer-like polyamidoamine and 5-sulfosalicylic acid

Silica-gel adsorbents PAMAM-n.0SSASG (n=1–4) with dendrimer-like polyamidoamine (PAMAM) and 5-sulfosalicylic acid as functional groups were prepared and characterized with FTIR, SEM, TG, elemental analysis and porous structure analysis. Micro-column enrichment and measurement of Pb2+ with graphite furnace atomic absorption spectroscopy (GFAAS) was studied with PAMAM-n.0SSASG (n=1–4) as adsorbent. It was emphasized to investigate the relationship between dynamic adsorption/desorption rates, adsorption capacities, and grafting percentage of PAMAM onto silica-gel surface. Experiments showed that the generation increase of grafted PAMAM changed the pore diameter distribution of adsorbent and obviously improved adsorption/desorption property for Pb2+. Adsorption capacity of PAMAM-n.0SSASG (n=1–4) was 14.04, 17.43, 20.07 and 25.05mgg−1 for Pb2+ respectively. An enrichment factor of 200 was obtained with PAMAM-4.0SSASG as adsorbent and with 2000mL Pb2+ solution (1.0ngmL−1). The priority of adsorption property of PAMAM-4.0SSASG was explained by steric hindrance effect of PAMAM on adsorption/desorption, and selective adsorption of 5-sulfosalicylic acid with Pb2+. With PAMAM-4.0SSASG as adsorbent, GFAAS method for analysis of Pb2+ combined with micro-column enrichment was proposed and applied to the determination of Pb2+ of standard reference sample and sea water sample.

Direct Synthesis of Methanol by Partial Oxidation of Methane with Oxygen over Cobalt Modified Mesoporous H-ZSM-5 Catalyst

Partial oxidation of methane over mesoporous catalyst cobalt modified H-ZSM-5 has been carried out. Mesoporous Na-ZSM-5 (Si/Al = 35.4) was successfully synthesized using double template method which has high surface area (450 m2/g) and average pore diameter distribution of 1.9 nm. The as-synthesized Na-ZSM-5 was converted to H-ZSM-5 through multi-exchange treatment with ammonium ion solution, causing decreased crystallinity and surface area, but increased porous diameter, due to dealumination during treatment process. Moreover, H-ZSM-5 was loaded with cobalt (Co = 2.5% w) by the incipient impregnation method and calcined at 550 °C. Partial oxidation of methane was performed in the batch reactor with 0.75 bar methane and 2 bar of nitrogen (with impurities of 0.5% oxygen) as the input at various reaction time (30, 60 and 120 min). The reaction results show that cobalt species in catalyst has an important role, because H-ZSM-5 cannot produce methanol in partial oxidation of methane. The presence of molecular oxygen increased the percentage of methanol yield. The reaction is time-dependent with the highest methanol yield (79%) was acquired using Co/H-ZSM-5 catalyst for 60 min.

Uniform Surface Modification of 3D Bioglass(®)-Based Scaffolds with Mesoporous Silica Particles (MCM-41) for Enhancing Drug Delivery Capability.

The design and characterization of a new family of multifunctional scaffolds based on bioactive glass (BG) of 45S5 composition for bone tissue engineering and drug delivery applications are presented. These BG-based scaffolds are developed via a replication method of polyurethane packaging foam. In order to increase the therapeutic functionality, the scaffolds were coated with mesoporous silica particles (MCM-41), which act as an in situ drug delivery system. These sub-micron spheres are characterized by large surface area and pore volume with a narrow pore diameter distribution. The solution used for the synthesis of the silica mesoporous particles was designed to obtain a high-ordered mesoporous structure and spherical shape – both are key factors for achieving the desired controlled drug release. The MCM-41 particles were synthesized directly inside the BG-based scaffolds, and the drug-release capability of this combined system was evaluated. Moreover, the effect of MCM-41 particle coating on the bioactivity of the BG-based scaffolds was assessed. The results indicate that it is possible to obtain a multifunctional scaffold system characterized by high and interconnected porosity, high bioactivity, and sustained drug delivery capability.

Chemical synthesis and characterization of Nb–ZrO2

The effects of doping of ZrO with pentavalent ions have been insufficiently studied, given that some results indicate that doping does not suppress the monoclinic-tetragonal transformation of the material. To assess the influence of Nb and the calcination conditions on the morphology of ZrO2 in this study, ZrO2:Nb was prepared with dopant concentrations of 2.5mol%, 5.0mol% and 7.5mol%, and was microwave and conventionally calcined at temperatures of 500–1000°C. The XRD results revealed the presence of the orthorhombic, tetragonal and monoclinic phases of ZrO2 and the orthorhombic phase of Nb2Zr6O17. The Rietveld refinement indicated a volumetric fraction of more than 96% of the orthorhombic phase. Raman vibrational modes indicate the presence of tetragonal phase in all the samples and coexistence with other phases at higher temperatures. SEM micrographs of niobium-doped zirconia powders indicated the growth of particles with sizes varying from 1μm to 20μm, in response to increasing heat treatment temperatures and Nb content. The nitrogen adsorption–desorption isotherms of the sample revealed the presence of IV and V type isotherms characteristic of mesoporous materials. The average pore diameter distribution vs. incremental pore volume confirmed the existence of mesopores, whose average diameter was influenced by both dopant and temperature.

Nb–Al diffusion reaction in high Nb containing TiAl porous alloys

High Nb containing TiAl porous alloys were synthesised by powder metallurgy (PM). In order to reveal reaction mechanism of Nb in preparation of the porous alloys, Nb–Al diffusion reaction was investigated using diffusion couples at relatively low temperatures of 600–800°C. The porous Nb–Al diffusion layer was identified as NbAl3 phase and the thickness of diffusion layer indicated that the Nb–Al diffusion mainly occurred at 800°C. In addition, the pore diameter distribution indicated that Nb–Al diffusion also contributed to the increase in pore diameter. According to these results, the diffusion reaction model was established for high Nb containing TiAl porous alloys.

Oxide ceramics with unidirectional pore channels by electrophoretic deposition

Disc-shaped alumina, alumina-toughened zirconia, and mullite green bodies, few millimetres in thickness, with parallel aligned pore channels were produced by an electrophoretic deposition method that takes advantage of the gas generation by electrolysis in aqueous suspensions. Appropriate amounts of an anionic polyelectrolyte, chosen on the basis of zeta potential measurements, and ammonia solution were used as additives. Adding ammonia promoted the gas evolution at a given polyelectrolyte amount. The electrolyte content influenced the porosity values and the diameters of the pore channels. Volume fractions of the pore channels in the sintered bodies up to 40% were determined by computed tomography in combination with 3D image analysis. The maxima of the pore diameter distributions of the sintered samples were in the range between 200 and 300μm.

Impact of Nano-Pore Structure in Harden Non-Sintering Cement.

This study investigates the nano pore structure of non-sintering cement (NSC) matrix. The result of pore structure properties showed no considerable difference in the total pore volume, but presented a large distinction in distribution of pore diameter by cement mixing ratio. The pore-diameter of NSC paste shows that occupation ratio of pore diameter below 10 nm was larger and was smaller than ordinary Portland cement (OPC) and blast-furnace slag cement (BSC) at pore diameter of over 10 nm. The reasons are due to the hydrate such as C-S-H gel and ettringite which formed dense nano pore structure of NSC matrix.

Experimental study of sealing performance:2. Effects of particle size distribution on threshold pressure of sintered compacts

AbstractIn connection with an assessment of the sealing performance of a caprock such as mudstone for geologic CO2 sequestration, we prepared sintered compacts comprising two different‐sized silica beads with various particle size ratios and mixing ratios. Then we examined the correlation between permeability k and threshold pressure Pcth of the samples. Specifically, Pcth was measured in supercritical CO2‐water system under conditions of 1000 m depth (10 MPa and 40°C). A series of studies was conducted to identify factors affecting data variability on the Pcth‐k correlation chart and to ascertain the variation ranges of both parameters. This paper corresponds to a second step of work, following previous measurements obtained from monodisperse samples. The sample's k showed good correlation with both the mixing ratio and mean area diameter, whereas Pcth with great variation was correlated with neither parameter. In this context, results suggest that Pcth, which was controlled by local structures within samples, could not be predicted simply from the pore diameter distribution. Regarding the Pcth‐k correlation, monodisperse samples are scattered around the closest‐packing line. In contrast, bidisperse samples are shown mainly below the closest‐packing line. Moreover, the slope of a fitting line on the Pcth‐k double logarithmic chart was lowered from −0.62 for monodisperse particles to −0.43 for bidisperse particles. Nevertheless, the low slope on mudstone cannot be explained solely by the effect of the particle size distribution. Therefore, the contribution of the particle configuration is expected to be greater as a factor affecting the internal structure of mudstone.

Porous YbB6 Ceramics Prepared by In Situ Reaction between Yb2O3 and B4C Combined with Partial Sintering

Porous YbB6 ceramic, a member of the ultrahigh‐temperature (UHT) family, is successfully prepared from Yb2O3 and B4C powders by in situ synthesis combined with partial sintering method. Due to the fact that pores can be produced using the gases such as B2O3 and CO generated in reaction between Yb2O3 and B4C, phase‐pure porous YbB6 ceramics are obtained after sintering the Yb2O3/B4C green bodies at 1750°C for 2 h in a flowing argon atmosphere under ambient pressure without addition of pore‐forming agent. Using this new and simple method, the porosity and volume shrinkage of porous YbB6 ceramics are controllable by changing the green density. The prepared porous YbB6 ceramic has homogeneous pore structure with very narrow pore diameter distribution. Furthermore, the porous YbB6 possesses high compressive strength of ~21.34 MPa when the porosity is ~58.7% and the density is ~2.27 g/cm3. The combination of these favorable properties renders porous YbB6 ceramic being a light‐weight structural and functional component for UHT applications.

Characteristics of silty laminae in Zhangjiatan Shale of southeastern Ordos Basin, China: Implications for shale gas formation

Shale oil and gas have been discovered in the lacustrine organic-rich Zhangjiatan Shale of the Upper Triassic Yanchang Formation, Ordos Basin, China. Core observations indicate abundant silty laminae in the producing shales. This study documents the stratigraphic distribution of silty laminae and their relationship with interlaminated clay laminae. The type, structure, and characteristics of pores and mineral composition of silty laminae were observed and analyzed through thin section and scanning electron microscopy, X-ray diffraction, low-pressure ![Formula][1] and ![Formula][2] adsorption, mercury porosimetry, and helium pycnometry. Results from silty laminae are compared with those of clayey laminae. The frequency and thickness of silty laminae vary over a wide range. The thickness ranges from 0.2 to 4 mm and is 1.5 mm on average; the frequency ranges from 4 to 32 laminae/m and is 23 laminae/m on average. The thickness percentage of silty laminae in the measured segments ranges from 6% to 17%. Silty laminae consist of quartz, feldspar, mixed-layer montmorillonite, and chlorite. In comparison to clayey laminae, non-clay detrital grains are larger, quartz and feldspar are more common, and clay minerals are less abundant. Pores in silty laminae are primary interparticle, dissolutional, intercrystalline, and microfracture types. Mesopores (2–50 nm in diameter) and macropores (50 nm–1 μm) are common, whereas, micropores ![Formula][3] are rare; the distribution of pore diameters is multimodal. However, microscopic pores with a diameter commonly smaller than 100 nm are common in clayey laminae. Thus, pore volume and surface area of micropores in silty laminae are less than those in the adjacent clayey laminae, and vice versa for meso- and macropores. The porosity of shales increases with the proportion of silty laminae in the shales. The silty laminae provide the storage space and flow conduit for oil and gas, and they play a significant role in the migration, accumulation, occurrence, and amount of gas in the shales. [1]: /embed/mml-math-1.gif [2]: /embed/mml-math-2.gif [3]: /embed/mml-math-3.gif