Microporous Properties Research Articles

Effect of solution treatment on micropore and mechanical properties of DD6 superalloy

Effect of solution treatment on the micropore and mechanical properties is investigated for the DD6 superalloy. The results show that solution treatment has positive and negative effects on the DD6 superalloy, which can weaken the segregation significantly. After solution treatment, the segregation ratio of the major alloying elements tends to 1. However, the amount of micropores increases with increasing solutionising time and can reach 0.46%, which is one order of magnitude higher than that of the as-cast superalloy. The hardness increases slightly, especially for the superalloy solutionised at 1310°C with a 5% increase in hardness compared to the as-cast superalloy. Hardness, tensile and stress rupture properties of the DD6 superalloy can reach the best after solution treatment at 1310°C and 4 h.

Adsorptive removal of cationic methylene blue and anionic Congo red dyes using wet-torrefied microalgal biochar: Equilibrium, kinetic and mechanism modeling.

This study aims to investigate the adsorption behavior of cationic and anionic dyes of methylene blue (MB) and Congo red (CR) onto wet-torrefied Chlorella sp. microalgal biochar respectively, as an approach to generate a waste-derived and low-cost adsorbent. The wet-torrefied microalgal biochar possessed microporous properties with pore diameter less than 2nm. The optimum adsorbent dosage of wet-torrefied microalgal biochar for MB and CR dyes removal were determined at 1g/L and 2g/L, respectively, with their natural pHs as the optimum adsorption pHs. The determined equilibrium contact times for MB and CR were 120h and 4h, respectively. Based on the equilibrium modeling, the results revealed that Langmuir isotherm showed the best model fit, based on the highest R2 coefficient, for both the adsorption processes of MB and CR using the wet-torrefied microalgal biochar, indicating that the monolayer adsorption was the dominant process. From the modeling, the maximum adsorption capacities for MB and CR were 113.00mg/g and 164.35mg/g, respectively. The kinetic modeling indicated the adsorption rate and mechanism of the dyes adsorption processes, which could be crucial for future modeling and application of wet-torrefied microalgal biochar. From the results, it suggests that the valorization of microalgae by utilizing wet-torrefied microalgal biochar as the effective adsorbent for the removal of toxic dyes with an approach of microalgal biorefinery and value-added application to the environment is feasible.

Study on the novel capacitive moisture sensing behaviour of nickel chromite nanoparticle based thick film

Abstract In this work, the novel and appreciable humidity sensing properties of microporous, spinel nickel chromite thick films are reported for the first time. NiCr2O4 microporous, thick film prepared by tape casting of sol-gel derived nanopowder followed by sintering was sandwiched between two parallel silver electrodes to develop capacitive humidity sensor. Condensation in the surface pores and physisorption on the sensor surface are found to be responsible for the humidity sensing properties. The sensor shows excellent humidity sensing properties in the range of 5 to 95% RH (relative humidity) with a resolution of ∼3 pF/%RH in the lower humidity range (5% - 30% RH) at 1kHz external electric field. The sensor also exhibited excellent repeatability (at least 50 cycles of 5%-95%RH), good stability of at least 6 months, and low hysteresis loss. The thick film sensors were characterized by XRD, FT-IR, FESEM, TEM, EDX, and contact angle measurement.

Pore Morphology, Porosity, and Pore Size Distribution in Kaolinitic Remolded Clays under Triaxial Loading

Abstract This work aims to investigate the micropore properties of saturated kaolin subjected to triaxial loading. Consolidated drained triaxial compression tests were conducted on both normally co...

Fractal Characteristics of Micro- and Mesopores in the Longmaxi Shale

To better understand the variability and heterogeneity of pore size distributions (PSDs) in the Longmaxi Shale, twelve shale samples were collected from the Xiaoxi and Fendong section, Sichuan Province, South China. Multifractal analysis was employed to study PSDs of mesopores (2–50 nm) and micropores (<2 nm) based on low-pressure N2/CO2 adsorption (LP-N2/CO2GA). The results show that the PSDs of mesopores and micropores exhibit a multifractal behavior. The multifractal parameters can be divided into the parameters of heterogeneity (D−10–D10, D0–D10 and D−10–D0) and the parameters of singularity (D1 and H). For both the mesopores and micropores, decreasing the singularity of the pore size distribution contributes to larger heterogeneous parameters. However, micropores and mesopores also vary widely in terms of the pore heterogeneity and its controlling factors. Shale with a higher total organic carbon (TOC) content may have a larger volume of micropores and more heterogeneous mesopores. Rough surface and less concentrated pore size distribution hinder the transport of adsorbent in mesopores. The transport properties of micropores are not affected by the pore fractal dimension.

Comparison of the ionic conductivity properties of microporous and mesoporous MOFs infiltrated with a Na-ion containing IL mixture.

IL@MOF (IL: ionic liquid; MOF: metal-organic framework) materials have been proposed as a candidate for solid-state electrolytes, combining the inherent non-flammability and high thermal and chemical stability of the ionic liquid with the host-guest interactions of the MOF. In this work, we compare the structure and ionic conductivity of a sodium ion containing IL@MOF composite formed from a microcrystalline powder of the zeolitic imidazolate framework (ZIF), ZIF-8 with a hierarchically porous sample of ZIF-8 containing both micro- and mesopores from a sol-gel synthesis. Although the crystallographic structures were shown to be the same by X-ray diffraction, significant differences in particle size, packing and morphology were identified by electron microscopy techniques which highlight the origins of the hierarchical porosity. After incorporation of Na0.1EMIM0.9TFSI (abbreviated to NaIL; EMIM = 1-ethyl-3-methylimidazolium; TFSI = bis(trifluoromethylsulfonyl)imide), the hierarchically porous composite exhibited a 40% greater filling capacity than the purely microporous sample which was confirmed by elemental analysis and digestive proton NMR. Finally, the ionic conductivity properties of the composite materials were probed by electrochemical impedance spectroscopy. The results showed that despite the 40% increased loading of NaIL in the NaIL@ZIF-8micro sample, the ionic conductivities at 25 °C were 8.4 × 10-6 and 1.6 × 10-5 S cm-1 for NaIL@ZIF-8meso and NaIL@ZIF-8micro respectively. These results exemplify the importance of the long range, continuous ion pathways contributed by the microcrystalline pores, as well as the limited contribution from the discontinuous mesopores to the overall ionic conductivity.

Microporosity Clustering Assessment in Calcium Phosphate Bioceramic Particles.

There has been an increase in the application of different biomaterials to repair hard tissues. Within these biomaterials, calcium phosphate (CaP) bioceramics are suitable candidates, since they can be biocompatible, biodegradable, osteoinductive, and osteoconductive. Moreover, during sintering, bioceramic materials are prone to form micropores and undergo changes in their surface topographical features, which influence cellular physiology and bone ingrowth. In this study, five geometrical properties from the surface of CaP bioceramic particles and their micropores were analyzed by data mining techniques, driven by the research question: what are the geometrical properties of individual micropores in a CaP bioceramic, and how do they relate to each other? The analysis not only shows that it is feasible to determine the existence of micropore clusters, but also to quantify their geometrical properties. As a result, these CaP bioceramic particles present three groups of micropore clusters distinctive by their geometrical properties. Consequently, this new methodological clustering assessment can be applied to advance the knowledge about CaP bioceramics and their role in bone tissue engineering.

UV-induced room temperature synthesis of microporous ladder polymers with efficient photosensitization

Microporous ladder polymers (MLPs) represent a beneficial combination of porosities and processability for advanced separation and catalysis. Yet MLPs synthesis is halted by tedious condensation reactions, excessive catalysts and limited choices of monomers. The work reports the first example of room temperature synthesis of MLPs (PAnTB) through photopolymerization of contorted bisanthracene monomers under 365 nm light irradiation, being catalyst-free and atom-economy. PAnTB highlight intrinsically microporous properties (specific surface area: 554 m2 g−1) and efficient photosensitization for the generation of singlet oxygen. This work opens the door to light-induced synthesis of MLPs with enriched monomer structures and functionalities, such as the metal-free degradation of organic contaminants using PAnTB alone under visible-light.

Effects of the Chemical Structure, Surface, and Micropore Properties of Activated and Oxidized Black Carbon on the Sorption and Desorption of Phenanthrene.

The effects of the chemical structure, surface properties, and micropore of modified black carbon samples (BCs) on the sorption mechanism of hydrophobic organic contaminants (HOCs) are discussed. Activated and oxidized BCs were produced from a shale kerogen at 250-500 °C by chemical activation regents (KOH and ZnCl2) and then by oxidative regents (H2O2 and NaClO). The surface properties (water contact angel, Boehm titration, and cation exchange capacity, CEC), structural properties (advanced solid-state 13C NMR), micropore properties (CO2 adsorption), mesopore properties (N2 adsorption), and sorption and desorption properties of phenanthrene were obtained. The results showed that ZnCl2-activated BCs had higher basic surface groups, CEC values, aromatic carbon contents, micropore volumes, and adsorption volumes but exhibited lower acidic surface groups than the KOH-activated BCs did. Micropore modeling and sorption irreversibility indicated that the micropore filling was the main sorption mechanism of phenanthrene. In addition, ZnCl2 activated and NaClO oxidized BCs showed a nice regression equation between adsorption volumes and micropore volumes (CO2- V0) as follows: Q0' = 0.495 V0 + 6.28( R2 = 0.98, p < 0.001). Moreover, the contents of nonprotonated aromatic carbon, micropore volumes, and micropore sizes are the critical factors to micropore filling mechanism of phenanthrene on BCs. The size of fused aromatic rings was estimated from the recoupled 1H-13C dipolar dephasing, and the BC structural models at temperatures ranging from 300 to 500 were proposed. This finding improves our understanding of the sorption mechanism of HOCs from the perspectives of chemical structure and micropore properties.

The carbon dioxide, methane and nitrogen high-pressure sorption properties of South African bituminous coals

In this paper, we report the CO2, CH4 and N2 sorption isotherms of four dry South African bituminous coals at pressures up to 16 MPa at 55 °C. The sorption capacities of the samples with respect to the adsorbate gases decreased in the order: CO2 > CH4 ≈ N2 by weight, and CO2 > CH4 > N2 by volume. A new model, based on a hybrid Dubinin-Radushkevich and Henry law approach (DR-HH) provided substantially better fits to the sorption isotherm data than the previously used modified DR (M-DR) model. Obtained uncertainty metrics show that the DR-HH model generally returned lower error sum of squares (ESS) and root mean square (RMS) residuals, and higher quality of fit (QOF) compared to the M-DR model. The net heat of sorption, βEs, of the samples for the three adsorbate gases were generally low (8.5–12.8 kJ/mol), but comparable to previous determinations of other coals, indicating that physisorption was the dominating sorption mechanism. The sorption capacities of the samples were found to be rank-dependent as they decreased with increasing vitrinite reflectance and elemental carbon content. The micropore properties of the samples as measured by both CO2 low-pressure gas adsorption (LPGA) and small angle X-ray scattering (SAXS), impacted the sorption properties of the sample more than both the mesopore and macropore properties determined from N2 LPGA, SAXS, and mercury intrusion porosimetry. The sorption capacities of the samples were found to increase with increasing lithotypes abundance, suggesting that lithotype bandings enhances either the fluid transport processes or the micropore properties of the coal matrix. In addition, it has been demonstrated that critical properties of the adsorbate gases influenced their sorption properties.

The effect of Ag+ cations on the micropore properties of clinoptilolite and related adsorption separation of CH4 and N2 gases

In this study, we report on the effects of Ag+ cations exchange within clinoptilolite zeolite in relation to both the physicochemical and the gas adsorption characteristics. Clinoptilolites cation-exchanged with AgNO3 to varying degrees were investigated and the influence of naturally occurring cations (Mg2+, Ca2+, K+) distributed within the material is discussed. The morphology and elemental composition of the untreated clinoptilolite and the Ag+ cation exchanged variants were characterized by XRD, EDS, FTIR, and N2 sorption experiments performed at 77 K. From the pore property analysis, we show that a slight reduction in the micropore distribution occurs for the highly exchanged Ag+ clinoptilolite compared to the untreated clinoptilolite, indicating a likely decrease in the average effective micropore size. Equilibrium adsorption isotherms of CH4 and N2 were measured at 303 K. The adsorption uptake rate of both gases was also studied and it slowed by the addition of Ag+ cations. The modified samples showed decreasing adsorption capacity for the larger CH4 gas molecule, whereas adsorption of the smaller N2 gas was less affected. This effect was most pronounced for the highly exchanged Ag+ clinoptilolite samples (AgNO3 exchange solution above 0.2M) whereby more N2 was adsorbed than CH4. At 1 atm and 303 K, the N2/CH4 equilibrium selectivity values of highly exchanged Ag+ clinoptilolite ranged from 2.8 to 7.6, which are higher than many clinoptilolite types.

A microporous Tb-MOF luminescent sensor based on a flexible tricarboxylate for highly sensitive detection of acetone and Fe3+ ions in aqueous and isopropanol

One novel microporous terbium (III) framework, [Tb(DBB)(H2O)2](1), has been prepared from 4-(3,5-dicarboxylatobenzyloxy) benzoic acid (DBB) with terbium salt under hydrothermal condition. Structural analysis shows complex 1 possesses three-dimensional frameworks based on 2D double sheets linking by DBB ligands into porous channels. The gas adsorption experiments of N2 and CO2 show that complex 1 possesses microporous properties. Fluorescence analyses exhibit the characteristic luminescence of Tb3+ ion both in solid state and in aqueous. In particular, the Tb-MOF can detect acetone for its luminescence entirely quenching in acetone. Furthermore, the ionic detection experiments indicate complex 1 could be a good sensor for highly and sensitively sensing Fe3+ ion in aqueous and isopropanol, and the detection limit could reach at 10−9 M in aqueous.

Ultrafine CuO nanoparticles decorated activated tube-like carbon as advanced anode for lithium-ion batteries

Recently, copper oxide (CuO) as promising anode material for lithium-ion batteries (LIBs) has received much interest. Hybridizing CuO with carbon is considered as a valid way to improve the conductivity and alleviate the volume effect of CuO, but how to achieve more optimized utilization rate of CuO-based anodes still remains a big challenge for us. In this work, activated tube-like carbon (ATC) is firstly prepared by pre-carbonization followed by alkali etching process using palm tree bark hair as initial carbon source, then the ATC is used as carbon matrix to load CuO by a modified phase-transfer approach. As a result, ultrafine CuO nanoparticles decorated ATC (ATC/CuO) can be obtained. For comparison, we also synthesize tube-like carbon (TC) by a direct pyrolysis process, and obtain TC/CuO hybrid by similar loading method. The morphology, structure, composition and surface property of the two carbon matrixes and the corresponding C/CuO hybrids are all systematically investigated. The results show that ATC/CuO hybrid possesses rich COCu bond and unique ultrafine CuO structure, which is attributed to the co-effect of abundant oxygen-containing groups, large specific surface area and special microporous property of ATC matrix. Consequently, the ATC/CuO electrode exhibited much enhanced cycling stability and rate capability when compared to sole CuO and TC/CuO electrodes. Obviously, our work provides a good guidance on the design and development of advanced carbon/metal oxide-based anodes for LIBs.

Adsorption and removal of phenoxy acetic herbicides from water by using commercial activated carbons: experimental and computational studies

In this study, commercial activated carbons (GAB and CBP) were successfully used for the removal of two phenoxy acetic class-herbicides, 4-chloro-2-methyl phenoxy acetic acid and 2.4-dichlorophenoxy acetic acid (MCPA and 2.4-D) from aqueous solution. The adsorbent materials were characterized, and their equilibrium adsorption capacity was evaluated. The results suggest that the microporous properties of GAB activated carbon enhanced the adsorption capacity, in comparison to CBP carbon. Thus, the increasing in the ionic strength favored the adsorption removal of both pesticides, indicating that electrostatic interactions between the pollutant and the adsorbate surface are governing the adsorption mechanism, but increasing pH values decreased adsorption capacity. Experimental data for equilibrium was analyzed by two models: Langmuir and Freundlich. Finally, computational simulation studies were used to explore both the geometry and energy of the pesticides adsorption.

Self-assembly of metal\u2013organic polyhedra into supramolecular polymers with intrinsic microporosity

Designed porosity in coordination materials often relies on highly ordered crystalline networks, which provide stability upon solvent removal. However, the requirement for crystallinity often impedes control of higher degrees of morphological versatility, or materials processing. Herein, we describe a supramolecular approach to the synthesis of amorphous polymer materials with controlled microporosity. The strategy entails the use of robust metal–organic polyhedra (MOPs) as porous monomers in the supramolecular polymerization reaction. Detailed analysis of the reaction mechanism of the MOPs with imidazole-based linkers revealed the polymerization to consist of three separate stages: nucleation, elongation, and cross-linking. By controlling the self-assembly pathways, we successfully tuned the resulting macroscopic form of the polymers, from spherical colloidal particles to colloidal gels with hierarchical porosity. The resulting materials display distinct microporous properties arising from the internal cavity of the MOPs. This synthetic approach could lead to the fabrication of soft, flexible materials with permanent porosity.

Effects of Cerium, Iron and Copper Incorporation on the Structural Properties and Activities of Ti-Pillared Bentonites

Ti-pillared bentonite (Ti-PB) using bentonite from the Middle Anatolia region (Hançılı) was synthesized. Iron or copper was impregnated to Ti-PB from the solution and subsequent cerium incorporation was done by wet impregnation. The hydrothermal syntheses were carried out with a Cu/(Cu+Ti) ratios of 0.1 and 0.2. The anatase phase of titanium dioxide was found for all of the samples. The Ti-PB calcined at 500 °C gave a basal spacing value of 4.41 nm, a specific BET surface area of 348 m2 g-1, and a micropore volume of 0.093 cm3g-1. While the post incorporation of copper and iron caused decrease in the micropore properties, the hydrothermally synthesized copper titanium samples reflected the similar behavior with Ti-PB. Energy dispersive X-ray spectroscopy (EDS) analyses indicated that TiO2 content of all PBs was near 40 wt % and metal incorporation to Ti-PB was succesfully performed by the impregnation method. Ti-PB exhibited both the Lewis and Brønsted acidities. The copper impregnation resulted in an increase in the Lewis acidity. The hydrotermally synthesised copper containing sample and cerium-iron and cerium-copper impregnated samples yielded an increase in the Brønsted acidity. Approximately 90 % phenol conversion at 30 °C in an hour was achived with the cerium and iron containing sample and the completion of photocatalytic oxidation was reached at 2 hours. An increase of temperature rised the conversion of phenol, and the iron containing sample resulted in approximately 100 % conversion at an hour at 50 °C. Hydroquinone, benzoquinone and catechol and formic, malic, fumaric acids were observed as the reaction intermediates. The leaching of metals was observed at low values and the stability of iron was found six times higher than the copper.

Identification of the Basic Sites on Nitrogen-Substituted Microporous and Mesoporous Silicate Frameworks Using CO2 as a Probe Molecule.

Carbon dioxide was shown to identify surface basic properties of nitrogen-substituted microporous and mesoporous silicas, in addition to conventional basic oxides, by a detailed study using isotherm and heat of adsorption measurements as well as by infrared spectroscopy. A hydrogen-bonded weak interaction was primarily observed between CO2 and silanol (Si-OH) and silamine (Si-NH-Si) groups. The heat of adsorption of CO2 demonstrated that the latter adspecies were formed preferentially over the former, although a much higher amount of linear CO2 adspecies were found on SBA-15 mesoporous silica because of the presence of a large quantity of silanol groups on its surface. Carbamate-type chemisorbed adspecies were not detected on silamino sites, whereas carbonate-type adspecies were formed on alkali ion-exchanged zeolites and also residual sodium ions on the surface of silicalite-1. CO2 was shown to be a successful probe molecule for identifying weakly interactive hydrogen-bonding sites, and it has potential as a surface probe for strongly interactive nucleophilic sites derived from alkaline ions or a methylated silamino group, Si-N(CH3)-Si.

Porosimetric features of calcium sulfoaluminate and Portland cement pastes: testing protocols and data analysis

Investigating pore structure of calcium sulfoaluminate cement paste is significantly important to understand the hydration process of cement, to develop the models that describe the cement paste microstructure, and eventually to improve the properties of the cement paste such as shrinkage compensation and self-stressing. The history, manufacture, and hydration of calcium sulfoaluminate cement are investigated. Two most common experimental protocols, nitrogen sorption and mercury intrusion porosimetry, are systematically summarized with required theories for analysis of porosimetric features of the cement pastes. Both calcium sulfoaluminate and portland cement pastes were tested with a water-to-cement ratio of 0.4, 0.5, and 0.6 using the two test methods. Since the measurement range of pore diameter by the nitrogen sorption porosimetry is relatively narrow (about 0.3–300 nm), the microporous properties of cement paste can be well determined. The mercury intrusion porosimetry is useful to evaluate the porosimetric features of cement pastes including bulk durability due to the wide measurement range of pore diameter (approximately 3 nm–200 μm).

Macropore- and Micropore-Dominated Carbon Derived from Poly(vinyl alcohol) and Polyvinylpyrrolidone for Supercapacitor and Capacitive Deionization

We developed a kind of macropore- and micropore-dominated carbon (HPAC) derived from poly(vinyl alcohol) and polyvinylpyrrolidone for electric double-layer capacitive (EDLC) applications, e.g., supercapacitors and capacitive deionization (CDI). By comparing the EDLC performance of HPAC with those of ordered mesoporous carbon (OMC) and commercial activated carbon (AC), we evaluated the pore size effects. Cyclic voltammetry (CV) was employed for static and flowing CDI processes to identify the disparities between supercapacitors and CDI. HPAC exhibits a specific capacitance of 309 F g–1 at a specific current of 0.5 A g–1 (6 M KOH) in a three-electrode half-cell and has a salt removal capacity of 16.3 mg g–1 (1.2 V, 500 mg L–1 NaCl), which is better than those of AC and OMC. Cycling tests of HPAC in supercapacitors and CDI show excellent stability. The properties of HPAC, fine, hydrophilic, macroporous, and microporous, endow HPAC with the promising possibility of use in supercapacitors and capacitive deioni...

Micro-Scale Analysis of Liquid Water Breakthrough inside Gas Diffusion Layer for PEMFC Using X-ray Computed Tomography and Lattice Boltzmann Method

The main objective of this work is to predict the breakthrough pressure of liquid water transport through the gas diffusion layer (GDL) and/or micro porous layer (MPL) used in polymer electrolyte membrane fuel cells. The integration of structural GDL and MPL with Lattice Boltzmann Method is primary focused. The numerical predictions are also compared with experimental data. The interaction between liquid phase and different surface treatments of solid structures controls the evolution of liquid water and the change of capillary pressure. The geometries of GDLs and MPLs were obtained by three dimensional reconstructed micro-structure images from both nanometer and micrometer-scaled high spatial resolution X-ray computed tomography (CT). The predictions of water breakthrough pressure agree with the data observed in the experiment. They also reveal that the breakthrough pressure and liquid water evolution inside the GDL samples are different when the wetting properties of GDL and/or MPL are changed. The detailed microporous property can be obtained using high spatial resolution image from nanometer-scaled X-ray CT, a.k.a. Nano X-ray CT. Meanwhile, images from micrometer-scaled X-ray CT, a.k.a. Micro X-ray CT, give proper field of view to cover complete vision of porous materials, including cracks in the MPL.