Pore Blocking Effect Research Articles

Synthesis of Chiral MOF-74 Frameworks by Post-Synthetic Modification by Using an Amino Acid.

The synthesis of chiral metal–organic frameworks (MOFs) is highly relevant for asymmetric heterogenous catalysis, yet very challenging. Chiral MOFs with MOF‐74 topology were synthesised by using post‐synthetic modification with proline. Vibrational circular dichroism studies demonstrate that proline is the source of chirality. The solvents used in the synthesis play a key role in tuning the loading of proline and its interaction with the MOF‐74 framework. In N,N′‐dimethylformamide, proline coordinates monodentate to the Zn2+ ions within the MOF‐74 framework, whereas it is only weakly bound to the framework when using methanol as solvent. Introducing chirality within the MOF‐74 framework also leads to the formation of defects, with both the organic linker and metal ions missing from the framework. The formation of defects combined with the coordination of DMF and proline within the framework leads to a pore blocking effect. This is confirmed by adsorption studies and testing of the chiral MOFs in the asymmetric aldol reaction between acetone and para‐nitrobenzaldehyde.

Inhibitory role of citric acid in the adsorption of tetracycline onto biochars: Effects of solution pH and Cu2+

Biochar, a cost-effective carbonaceous material, has shown great promise in many applications such as soil remediation and wastewater treatment. Citric acid in soil and water environments may affect interactions between biochar and organic contaminants (e.g., tetracycline). To evaluate the effect of citric acid on the adsorption of tetracycline onto biochars, this study investigated the adsorption behavior of tetracycline onto biochars of two different pyrolysis temperatures (300 and 450 °C, referred to as BC_300 and BC_450) in the present of citric acid, accompanying with the effects of solution pH and Cu2+. The results indicated that citric acid significantly inhibited the adsorption of tetracycline onto both biochars, that was mainly due to the multi-mechanisms including pore blocking effect, surface adsorption sites competition, and steric hindrance induced by citric acid. Moreover, citric acid more significantly suppressed the adsorption of tetracycline onto the two biochars at pH 9.0 than at pH 5.0 and 7.0. Because increasing pH could promote electrostatic repulsion between the negative tetracycline and the negatively charged surface of biochars. Cu2+ had greater enhancing effect on the sorption of tetracycline onto BC_300 than BC_450 via cation-bridging effect. Meanwhile, citric acid inhibited the adsorption of tetracycline onto BC_300 to a larger extent than the adsorption onto BC_450 in the presence of Cu2+. That is possibly due to BC_300 has more surface oxygen-containing functional groups than BC_450. Thus, the effect of coexisting citric acid needs to be taken into account when biochar is increasingly used as an amendment in soil and water systems.

PH-Triggered Drug Release Controlled by Poly(Styrene Sulfonate) Growth Hollow Mesoporous Silica Nanoparticles.

In the current report, hollow mesoporous silica (HMS) nanoparticles were successfully prepared by means of a hard-templating method and further modified with poly(styrene sulfonate) (PSS) via radical polymerization. Structural analysis, surface spectroscopy, and thermogravimetric characterization confirmed a successful surface modification of HMS nanoparticles. A hairy PSS was clearly visualized by high-resolution transmission electron microscopy measurement, and it is grown on the surface of HMS nanoparticles. The Brunauer–Emmett–Teller surface area and average pore size of HMS nanoparticles were reduced after surface modification because of the pore-blocking effect, which indicated that the PSS lies on the surface of nanoparticles. Nevertheless, the PSS acts as a “nano-gate” to control the release of curcumin which is triggered by pH. The drug-release profile of unmodified HMS nanoparticles showed a stormed release in both pH 7.4 and 5.0 of phosphate buffer saline buffer solution. However, a slow release (9.92% of cumulative release) of curcumin was observed at pH 7.4 when the surface of HMS nanoparticles was modified by PSS. The kinetic release study showed that the curcumin release mechanism from PSS@HMS nanoparticles followed the Ritger–Peppas kinetic model, which is the non-Fickian diffusion. Therefore, the PSS-decorated HMS nanoparticles demonstrate potential for pH-triggered drug release transport.

Effect of Hydrophobic Surface Treatment in Lowering Ionic Transport into Concrete

The present study concerns hydrophobic surface treatments with silane‐based liquid and crème on the concrete surface against external ionic transport for the application to concrete pavement coating. To quantify their effectiveness in mitigating the ionic penetration, water absorption and chloride transport were measured. Especially, back‐scattered image analysis and the electrochemical impedance spectroscopy were used to identify the effect of pore‐blocking at the interface of coating agents and the concrete. As a result, the surface treatment with both liquid and crème could significantly reduce the water absorption and chloride ingresses at all depths of measured concrete, due to a modification of the porosity. Moreover, the surface treatment on concrete substrate increased the polarization resistance, thereby enhancing the resistance to ionic transport into the concrete, and the crème type was slightly more effective at the same dosage of treatment.

Adsorption behaviour and mechanism of the PFOS substitute OBS (sodium p-perfluorous nonenoxybenzene sulfonate) on activated carbon.

Perfluorooctane sulfonate (PFOS) was listed as a persistent organic pollutant by the Stockholm Convention. As a typical alternative to PFOS, sodium p-perfluorous nonenoxybenzene sulfonate (OBS) has recently been detected in the aquatic environment which has caused great concern. For the first time, the adsorption behaviour and mechanism of OBS on activated carbon (AC) with different physical and chemical properties were investigated. Decreasing the particle size of AC can accelerate its adsorption for OBS, while AC with too small particle size was not conducive to its adsorption capacity due to the destruction of its pore structure during the mechanical crushing process. Intra-particle diffusion had a lesser effect on the adsorption rate of AC with smaller particle size, higher hydrophilicity and larger pore size. Reactivation of AC by KOH can greatly enlarge their pore size and surface area, greatly increasing their adsorption capacities. The adsorption capacity of two kinds of R-GAC exceeded 0.35 mmol g−1, significantly higher than that of other ACs. However, increasing the hydrophilicity of AC would decrease their adsorption capacities. Further investigation indicated that a larger pore size and smaller particle size can greatly enhance the adsorptive removal of OBS on AC in systems with other coexisting PFASs and organic matter due to the reduction of the pore-blocking effect. The spent AC can be successfully regenerated by methanol, and it can be partly regenerated by hot water and NaOH solution. The percentage of regeneration for the spent AC was 70.4% with 90°C water temperature and up to 95% when 5% NaOH was added into the regeneration solution. These findings are very important for developing efficient adsorbents for the removal of these newly emerging PFASs from wastewater and understanding their interfacial behaviour.

Removal of polycyclic aromatic hydrocarbons by nanofiltration membranes: Rejection and fouling mechanisms

Polycyclic aromatic hydrocarbons (PAHs), as a group of micropollutants with high toxicity, are commonly detected in the environment and difficult to remove. In this work, five commercial polyamide (PA) nanofiltration (NF) membranes were used to treat three PAHs in the synthetic solution or coking wastewater and their removal mechanisms were discussed. By comparing water permeability and PAHs rejections of the NF membranes before and after PAHs adsorption, we found that the PAHs adsorption into the membrane was the dominant rejection mechanism at the initial filtration stage. Due to the limited adsorption capacity and increasing diffusion of PAHs in the membrane, the PAHs rejections would drop rapidly and then reach steady. Size exclusion mechanism was also important to PAHs removal by NF, especially for PAHs with weaker polarity and higher molecular weight. Although the polysulfone intermediate layer could adsorb substantial PAHs resulting in an increase of filtration resistance, the pore blocking and narrowing effects on the PA separation layer were still the main reasons for the permeability loss of NF membranes. However, the glucose rejection did not change obviously after the PAHs adsorption in the membrane. Through analyzing porosity and pore size distribution of the NF membranes before and after PAHs adsorption, we found that for the NF membrane with small pore size and narrow pore size distribution (e.g. NF270), PAHs adsorption produced indiscriminate pore blocking effect, and thus the average pore size and its distribution as well as glucose rejection did not change obviously after fouling formation; while for the NF membrane with large pore size and wide pore size distribution (e.g. NF10), PAHs adsorption occurred more seriously in the larger pores leading to a pore narrowing effect, but the reduced pore size was still too large to affect glucose rejections. The outcomes of this work suggested that the PAHs adsorption in both separation and intermediate layers of NF membranes should be avoided, and the NF membrane with narrow pore size distribution was preferred for PAHs removal.

Pore structure characterization of coconut shell char with narrow microporosity

To get more insight into the pore structure characterization of nanoporous biomass chars, different probe molecules, models, and calibration steps were used and compared. The coconut shell chars (CSCs) were prepared under a steam atmosphere and characterized using N2, Ar, and CO2 adsorption. The results show that coconut shell chars are suitable for further activation, due to the high carbon content and abundant porosity. Ar adsorption with application of Non-Local Density Functional Theory (NLDFT) model can more accurately characterize the pore structure of CSC. When the calibration step is performed before adsorption measurement, the important results of N2 and Ar adsorption, such as pores size distribution (PSD) and isotherm, are affected by pore blocking, leading to the erroneous understanding of CSC in special applications. Vacuum treatment at 273 K for 1 h after He calibration is enough to remove He, which could reduce effect of pore blocking.

Synthesis of porous polymer-based metal–organic frameworks monolithic hybrid composite for hydrogen storage application

Herein, we report a simple method for the preparation of cross-linked polymer of intrinsic microporosity (PIM-1)/Materials Institute Lavoisier chromium (III) terephthalate [MIL-101(Cr)] monoliths which involves direct impregnation of PIM-1 with MIL-101(Cr) powder by physical mixing in tetrachloroethane solvent. This procedure yields monoliths with high metal–organic framework (MOF) loading weight percentages of up to 80 wt% of MIL-101 powder with little loss of composite mechanical strength. From the nitrogen adsorption isotherms, it was observed that the PIM-1/80 wt% MIL-101(Cr) had good retention of MOF filler surface area and accessibility of its micropores with nearly no pore blocking effects. The hydrogen adsorption was also not far from the estimated hydrogen uptake capacity based on the MIL-101 weight percentage estimation. As a consequence of the highly porous nature of the hybrid material, PIM-1/MIL-101(Cr) composite has been considered as a promising material for inclusion in hybrid hydrogen storage cylinders. Moreover, these composites provided better handling compared to the crystalline powder MOFs without compromising the properties of MOF.

Accelerated and natural carbonation of concrete with high volumes of fly ash: chemical, mineralogical and microstructural effects.

Today, a rather poor carbonation resistance is being reported for high-volume fly ash (HVFA) binder systems. This conclusion is usually drawn from accelerated carbonation experiments conducted at CO2 levels that highly exceed the natural atmospheric CO2 concentration of 0.03–0.04%. However, such accelerated test conditions may change the chemistry of the carbonation reaction (and the resulting amount of CH and C–S–H carbonation), the nature of the mineralogical phases formed (stable calcite versus metastable vaterite, aragonite) and the resulting porosity and pore size distribution of the microstructure after carbonation. In this paper, these phenomena were studied on HVFA and fly ash + silica fume (FA + SF) pastes after exposure to 0.03–0.04%, 1% and 10% CO2 using thermogravimetric analysis, quantitative X-ray diffraction and mercury intrusion porosimetry. It was found that none of these techniques unambiguously revealed the reason for significantly underestimating carbonation rates at 1% CO2 from colorimetric carbonation test results obtained after exposure to 10% CO2 that were implemented in a conversion formula that solely accounts for the differences in CO2 concentration. Possibly, excess water production due to carbonation at too high CO2 levels with a pore blocking effect and a diminished solubility for CO2 plays an important role in this.

Preparation of NiO nanoparticles in mesoporous silica via eutectic freezing and freeze-drying of aqueous precursor salts

Abstract Immobilization of small metal oxide particles on a solid support by impregnation with solutions of metal salts is a common route of catalyst preparation. Here we explore a modification of this route, based on eutectic freezing of the aqueous precursor salts in the pores of SBA-15, and removal of water/ice by freeze-drying. The two-solvents method was used to selectively fill the pore space of SBA-15 with precursor salts (nickel acetate or nitrate). A morphological and structural analysis of the nickel oxide formed in the pores after thermal decomposition of the salts was performed and compared to samples obtained via conventional solvent evaporation. Immobilized NiO nanocrystallites prepared via eutectic freezing appeared in two morphologies: (a) rodlike particles of ca 5 nm diameter, i.e., somewhat smaller than the pore diameter of SBA-15 (7 nm); (b) species detectable by powder XRD and energy-dispersive X-ray spectroscopy (EDXS), but not by TEM. Nitrogen adsorption isotherms are sensitive to the distribution of NiO in the pores: Pore blocking effects appear in the desorption branch for samples containing rodlike NiO particles, but not in samples in which no particles are detectable by TEM.

Effect of pitch powder addition on the microstructure and properties of carbon blocks for blast furnace

The phase composition and microstructural evolution of pitch-containing matrix sample with additive of silicon had been compared with pitch-free or resin-containing matrix sample to illustrate the strengthening effect of pitch. Two different pitch powders (CARBORES@P and High temperature pitch) were then incorporated into carbon blocks, respectively and the effect of pitch powder addition on microstructure and properties of carbon blocks fired at 1000 °C and 1400 °C in a coke bed was evaluated systematically. The results showed that compared with amorphous carbonized resin, carbonized pitch was a kind of highly graphitized carbon and could react with silicon and form SiC whiskers at 1400 °C. In carbon blocks, pitch powder accelerated the formation of AlN at 1000 °C and growth of β-SiC whiskers at 1400 °C, respectively, which enhanced the cold compressive strength, thermal conductivity and hot metal erosion resistance of carbon blocks. Moreover, carbon blocks containing CARBORES@P pitch with higher carbon yield exhibited better properties because of formation of more ceramic whiskers. The strengthening mechanism of pitch powder for carbon blocks was attributed to the pore-blocking effect of pitch carbonization and more in-situ formed whiskers derived from the reaction between carbonized pitch with silicon at 1400 °C.

Water-selective adsorption sites on detonation nanodiamonds

Nanodiamond particles form aggregates having porosity in the range of micropores to mesopores with an average pore diameter of 4.5 nm. The measured porosity depends on the removal of pre-occupied water and gases from the nanodiamond aggregates, which is sensitive to thermal treatments. We heated hydrogel nanodiamonds at 423–623 K in vacuo in order to understand the relationship between water adsorptivity and pore structure evaluated from nitrogen and argon adsorption isotherms at 77 K and 87 K, respectively. Temperature-programmed evolved gas analysis showed the evolution of water and CO2 on heating nanodiamonds in vacuo up to 700 K. The surface functional groups of nanodiamonds were not affected by the thermal treatments, as shown by FTIR and XPS analyses. However, the water adsorptivity was enhanced by heating at 623 K due to the removal of the pore blocking effect originated from water molecules selectively adsorbed. Water molecules adsorbed on these selective sites should cause the intensive hygroscopic property of nanodiamonds.

Impact of inherent moisture on the methane adsorption characteristics of coals with various degrees of metamorphism

Gas and water coexist in coal reservoirs. Many scholars have examined the effect of moisture on the gas adsorption property of coal. In this paper, the oxygen-containing functional groups and pore characteristics of five coal samples with different degrees of metamorphism were studied by Fourier transform infrared (FTIR) spectroscopy and CO2 adsorption method, and methane adsorption tests were carried out on coal samples with different inherent moisture contents. The water-holding capacities of different rank coals are related to their oxygen-containing functional groups and micropores characteristics, and the former play a decisive role. This is probably the main reason why low rank coals have stronger water-holding capacity than medium and high rank coals. The Langmuir volume tends to decrease with increasing inherent moisture content for all of the samples, which can be attributed to hydrogen bonding between the coal macromolecules and water molecules. The relationship between the amount of adsorbed methane and the inherent moisture content can be characterized well using the linear and exponential models. And it can be found that the moisture effect coefficient is dependent on the coal rank. Further analysis indicates that the influence of inherent moisture on the methane adsorption capacity is more prominent for low rank coals, which is probably due to its greater hydrophilia and water-holding capacity. Whereas, the reduction in methane adsorption capacity is mainly controlled by the pore-blocking effect of adsorbed water for high rank coals, and the extent of the influence of inherent moisture is a little.

Li-Crown ether complex inclusion in MOF materials for enhanced H2 volumetric storage capacity at room temperature

The organometallic Li-Crown ether species, formed by the complexation of lithium cation with the hydrophobic 18Crown6 ether, has been included in three Metal-Organic-Frameworks (MOF) structures with different pore size: Cr-MIL-101, Fe-MIL100 and Ni-MOF-74. X-ray powder diffraction, thermogravimetric analysis, proton nuclear magnetic resonance, infrared spectroscopy and inductively coupled plasma atomic emission spectroscopy measurements have proved the successful incorporation of the organometallic units to the three MOFs without altering their crystalline structure. Hydrogen adsorption properties of the post-synthesis modified materials have been evaluated in a wide temperature (77–298 K) and pressure (1–170 bar) range conditions. The post-synthetic modification method used based on the MOF impregnation with a Li-Crown ether complex solution produced a partial pore blocking effect on the microporous Ni-MOF-74, reducing its hydrogen adsorption capacity. However, the inclusion of the crown-ether and particularly the Li-Crown ether complex resulted in an increase of the volumetric hydrogen adsorption capacity at room temperature for Cr-MIL101 and Fe-MIL-100, due to the pore volume reduction, higher confinement of H2 molecules in the cavities and the formation of new specific binding sites for H2 molecules. The inclusion of Li-Crown ether complex also enhances the H2 interaction with the mesoporous MOF structures, attributed to the additional electrostatic interactions produced by the presence of Li+ ions complexed to the crown ether molecules. Further work following this strategy to improve hydrogen adsorption capacity of mesoporous MOFs at room temperature should be extended to other MOF materials, checking its influence on their capacity for gas separation purposes.

Effect of inorganic surface treatment on surface hardness and carbonation of cement-based materials

Surface treatment is a simple way to improve quality of surface of cement-based materials and thus increase the resistance of cement-based materials to environmental aggressions. Magnesium fluorosilicate, waterglass, sodium fluorosilicate, and combination of waterglass and sodium fluorosilicate were used as surface treatment agents. Their effects on compressive strength, surface hardness and resistance to carbonation were studied. The experimental results indicated that magnesium fluorosilicate and waterglass decreased the carbonation depth and increased surface hardness of concrete, while their effects were limited on compressive strength. A greater reduction in carbonation was found when sodium fluorosilicate pretreatment was used, because it could not only accelerate the hardness of waterglass but also react with cement. A liner relationship between Autoclam air permeability index and carbonation depth was found in all the treated concrete. Meanwhile, effects of treatments on morphology and microstructure were investigated by scanning electron microscope (SEM). Pore-blocking effects of inorganic surface treatment agents and new reaction products were observed.

Effect of pore geometry on nitrogen sorption isotherms interpretation: A pore network modeling study

Hydrocarbon-bearing tight rocks usually have pores at nanometer scale and permeability below microdarcy range. An effective characterization of the pore structure is essential for understanding hydrocarbon storage and transport behaviors. Nitrogen sorption isotherms measured at 77 K have been widely used for pore size and surface area characterization of nanoporous media. However, most analysis efforts are based on the assumption of slit or cylindrical pore shapes. Unconventional rocks such as shale have complex pore geometries that can have a significant effect on the adsorption curve cumulative behavior. Thus, a proper understanding of the effect of the assumed pore shapes on the interpretation of pore structure from nitrogen sorption isotherms is required to assess the reliability of the analysis results. In this study, we apply the lattice density functional theory initially developed for a single pore to a network of pores with bimodal pore size distribution and three types of pore shapes (i.e. slit, cylindrical and spherical). We simulate the nitrogen adsorption and desorption processes with incorporation of pore blocking effect and tensile strength effect. We optimize the pore size distribution, connectivity, surface area and surface energy for each type of pore shape by matching simulation and experimental sorption curves. We apply the above workflow to the sorption curves collected on Cameo coal and Woodford shale samples. For both samples, a network of spherical pores always results in the largest average pore size, highest surface energy, highest degree of connectivity but smallest surface area, while a network of slit pores shows the opposite. At the same time, all three types of pore shapes demonstrate a good match with experimental sorption curves. In terms of providing the closest match of surface area with BET results, we determine the dominant pore shape of Cameo coal and Woodford shale samples to be slit and cylindrical, respectively. To reduce the uncertainty in the characterization results, we further use a combination of all three types of pore shapes in our pore network model, with fractions of each pore shape determined by SEM image analysis. The final matching results show significant improvement over using only slit pore shape.

Organo-petrographic and pore facets of Permian shale beds of Jharia Basin with implications to shale gas reservoir

The shale deposits of Damodar Valley have received great attention since preliminary studies indicate their potential for shale gas. However, fundamental information allied to shale gas reservoir characteristics are still rare in India, as exploration is in the primary stage. In this study, Barakar shale beds of eastern part of Jharia Basin are evaluated for gas reservoir characteristics. It is evident that Barakar shales are carbonaceous, silty, contains sub-angular flecks of quartz and mica, irregular hair-line fractures and showing lithological variations along the bedding planes, signifying terrestrial-fluviatile deposits under reducing environment. The values of TOC varies from 1.21 wt.% to 17.32 wt.%, indicating good source rock potentiality. The vitrinite, liptinite, inertinite and mineral matter ranging from 0.28 vol.% to 12.98 vol.%, 0.17 vol.% to 3.23 vol.%, 0.23 vol.% to 9.05 vol.%, and 74.74 vol.% to 99.10 vol.%, respectively. The ternary facies plot of maceral composition substantiated that Barakar shales are vitrinite rich and placed in the thermal-dry gas prone region. The low values of the surface area determined following different methods point towards low methane storage capacity, this is because of diagenesis and alterations of potash feldspar responsible for pore blocking effect. The pore size distribution signifying the micro to mesoporous nature, while Type II sorption curve with the H2 type of hysteresis pattern, specifies the heterogeneity in pore structure mainly combined-slit and bottle neck pores.

Effects of humic acid and heavy metals on the sorption of polar and apolar organic pollutants onto biochars

The effects of humic acid (HA) and heavy metals (Cu2+ and Ag+) on the sorption of polar and apolar organic pollutants onto biochars that were produced at temperatures of 200 °C (BC200) and 700 °C (BC700) were studied. Due to the plentiful polar functional groups on BC200, cationic propranolol exhibited higher levels of sorption than naphthalene on BC200 while naphthalene and propranolol showed similar sorption capacities on BC700. HA changed the characteristics of biochars and generally inhibited the sorption of target organic pollutants on biochars; however, enhancement occurred in some cases depending on the pollutants involved and their concentrations, biochars used and the addition sequences and concentrations of HA. On BC200, HA modifications mainly influenced sorption by decreasing its polarity and increasing its aromaticity, while on BC700, the surface area and pore volume greatly decreased due to the pore-blocking effects of HA. Residue dissolved HA in solution may also contribute to sorption inhibition. Complexation between polar functional groups on BC200 and heavy metals slightly enhanced the sorption of neutral naphthalene and significantly enhanced that of anionic 4-nitro-1-naphtol, while limited the sorption of cationic propranolol. Heavy metals together with their associated water molecules decreased the sorption of target chemicals on BC700 via pore-filling or pore-mouth-covering. Inhibition of heavy metals for 4-nitro-1-naphthol was found to be the weakest due to the bridge effects of heavy metals between 4-nitro-1-naphtol and BC700. The higher polarizability of Ag+ led to the increase of its sorption on biochars in the presence of organic aromatic pollutants. The results of the present study shed light on the sorption mechanisms of bi-solute systems and enable us to select suitable biochar sorbents when chemicals co-exist.

Permeability evolution study after breaking of friction reducer in near fracture matrix of tightgas reservoir

Hydraulic fracturing is generally required for tightgas formation with low matrix permeability to achieve economic production rate. Slickwater fracturing is one of most commonly used technology. Friction reducer is the primary component of this fluid. During fracturing, million gallons of friction reducer fluid are pumped downhole to initiate fractures, and lots of fluid would filtrate into formation matrix. Due to the small pore size of tightgas reservoir, breaking of the friction reducer fluid is required to minimize formation damage and improve the conductivity in fracture. However, this performance in tightgas is not clear.In this paper, tightsand samples were treated with a friction reducer and a breaker to simulate the filtration process during hydraulic fracturing. Three breaking scenarios were proposed and studied correspondingly. Over balance breaking resulted in higher permeability regain than balance and under balance breaking, which means less formation damage to the near fracture matrix. The short sample has a full recovery of permeability with over balance breaking and it is higher than that with balance and under balance breaking. With over balance breaking, 0.012wt% breaker recovers 79.5% permeability, and the permeability regain increases with higher breaker concentration. The permeability regain of longer sample is improved, up to 116.3%. With under balance breaking, 0.1vol% friction reducer shows 81.6% permeability regain. Lower concentration friction reducer achieves a higher permeability regain. The reasons can be attributed to pore blocking effect and wettability alteration introduced by the friction reducer and breaker. The emulsion particle size in the friction reducer solution is found to overlap with the pore size distribution of tightgas sandstone. Therefore, it was able to block the matrix pores in tightsand after treated with the friction reducer and breaker. The contact angle on sample surface was changed from 24.3° to 81.1° in average.

Insights into the redistribution of sulfur species during cycling in lithium-sulfur batteries using physisorption methods

Nitrogen physisorption was used to analyze textural transformations in lithium-sulfur cathodes during cycling for two alternate electrolyte systems. Significant impact of the electrolyte type on the accessible cathode porosity in the charged vs. discharged state was detected, providing important insights in the cells conversion mechanism and the role of polysulfide solubility. The main advantage of the method lies in the resolution of pore accessibility and size distributions. Thus, depending on the state of charge (SoC), the C-rate used for cycling as well as electrolyte properties (i.e. polysulfide solvation), significant differences in the redistribution of active sulfur species as well as pore blocking effects can be identified. This methodology might facilitate interpretation and further optimization to achieve long-term stable lithium-sulfur batteries.