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Biomaterials capable of continuously inactivating pathogens are essential for suppressing transmission of infectious diseases, such as epidemic cerebrospinal meningitis and pulmonary tuberculosis. Here, capillary condensation of air moisture within nano‐confined spaces between superhydrophilic rigid nanorods is shown and target microbiology spontaneously stretch and inactivate aerosolized microorganisms. Specifically, the negative Gaussian curvature‐shaped water condensate causes fluidic straining, comprising surface tension and Laplace pressure, strong enough to deform and eliminate the selected bacteria. Plate counting quantifies the sharply reduced contact‐killing period for superhydrophilic and bare nanorods (6 vs 100 min for E. coli, 20 vs 120 min for S. aureus) under relative humidity of 70%. Theoretical calculations and experimental studies indicate increased mechanical straining and mechano‐bactericidal by improving air moisture content. To further illustrate utility, long‐term antibacterial medical masks are fabricated by integrating such nanorods onto commercial fabrics. Collectively, these findings highlight the immense potential of capillary condensation‐induced fluidic straining as an eco‐friendly, broad‐spectrum, and highly efficient antibacterial strategy. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) serves as extensively researched adsorbents, with numerous established methods for their preparation. This study originated from the hypothesis that compressing a hydrocarbon substance to create a densely compacted pellet, known as pelletizing, would enhance the development of porous features of the resulting AC. The anticipated enhancement is attributed to the rise in spatial proximity amidst HEC polymer chains within the bulk of the pellet, which facilitates aromatization both in extent and functionality. 2-Hydroxyethyl cellulose (HEC) pellets were prepared by adjusting the duration of load holding, aiming to increase the packing density of HEC polymer chains via creeping. The BET analysis of the resulting AC samples demonstrates the efficacy of compression on HEC pellets in enhancing their porous properties. The FE-SEM study revealed diverse AC surface morphologies that are associated with a set of specific pelletizing conditions. The 13C NMR spectroscopy for carbon skeletons, FT-IR spectroscopy for organic functionality, and XPS spectroscopy for surface composition collectively report the leverage of compression treatment before pyrolyzing HEC pellets. Furthermore, the assessment of hydrogen sulfide adsorption by the resulting AC samples revealed distinctive breakthrough curves, providing validation for the proposed compression effect. [ABSTRACT FROM AUTHOR]

Hydrogen is an active substitute for current commercial fuels as a green energy source. However, the progress toward hydrogen economy is stalled due to a lack of efficient and economical storage systems usually restrained by the material used. Some specific issues still need to improve in recent practical hydrogen storage methods: low surface area, limited capacity to attract gas adsorbate, high-temperature medium for hydrogen desorption, and extreme reactivity towards Oxygen and air. The paper presents a study on the surface modification of silicon nanostructures (SiNSs) synthesized by chemical etching, followed by structure optimization to enhance the hydrogen storage capacity. The standard anodization method prepares porous silicon (PS) while metal-assisted chemical etching fabricates Si and Porous Si nanowires (PSiNWs) on Si and PS substrates. Morphological features like surface area and porous nature were evaluated using SEM, AFM, and BET to interpret the gas-surface interaction. The modified surface area and average roughness of SiNSs increase maximum to 437 m2 g−1 and 501 nm, respectively. The PS shows the highest gas-surface interaction (up to 86.6%) and surface energy due to uniform pore distributions and high surface area. The NMR and FTIR investigate the hydrogen termination on the surface, whereas TG-DSC indicates the desorption of surface hydrides at ∼290 °C. A rank matrix is constructed considering various adsorption-desorption and fabrication parameters to select optimized SiNS, whereas PS is selected as a suitable candidate for hydrogen storage. • Electrochemical anodization and metal-assisted chemical etching fabricate porous silicon and porous Si nanowires. • The gas physisorption improves in nanopores due to the overlap of attractive fields from adjacent pore walls. • High resistivity substrate Si nanostructures exhibit uniform and homogeneous pore size distribution. • Continuous water rinsing on the hydrogenated surface of Si nanostructures causes hydrogen desorption from the surface. • Porous silicon stands prominently and has a high potential for hydrogen storage based on the rank matrix. [ABSTRACT FROM AUTHOR]

Abstract—The study investigated the physicochemical and adsorption characteristics of a micro-mesoporous carbon adsorbent obtained from wood waste by a thermochemical method with respect to the processes of the accumulation of liquefied natural gas vapors in long-term storage systems. X-ray diffraction analysis of the adsorbent showed that, as a result of synthesis of the adsorbent, its structure was an amorphous carbon phase, without signs of graphite-like phases characteristic of coal obtained from other types of raw materials. In turn, the developed porous structure of the adsorbent is represented by both micro- and mesopores, with a wide size distribution: the total pore volume was about 1.7 cm3/g. The sorption characteristics of the adsorbent at temperatures of 111.7–160 K and pressures up to 0.6 MPa were calculated based on the linearity of experimental isotherms at T from 303 to 333 K and the contribution from adsorption on the surface of mesopores in the monolayer and the capillary condensation effect (CCE). Based on sorption data, it is shown that the presence of mesopores has a predominant effect on the adsorption accumulation efficiency due to the contribution of CCE, providing an active capacity of cryogenic sorption accumulators at a level of 450 m3(NTP)/m3. [ABSTRACT FROM AUTHOR]

Nanomaterial-based humidity sensors hold great promise for water vapor detection because of their high sensitivity and fast response/recovery. However, the condensation of water in nanomaterial films remains unclear from a physicochemical perspective. Herein, the condensation of water vapor in silica nanoparticle films was physicochemically analyzed to bridge the abovementioned gap. The morphology of surface-adsorbed water molecules was characterized using infrared absorption spectroscopy and soft X-ray absorption spectroscopy, and the effect of RH on the amount of adsorbed water was observed using a quartz crystal microbalance. The adsorbed water was found to exist in liquid- and ice-like states, which contributed to high and low conductivity, respectively. The large change in film impedance above 80% RH was ascribed to the condensation of water between the nanoparticles. Moreover, RH alteration resulted in a colorimetric change in the film's interference fringe. The obtained insights were used to construct a portable device with response and recovery times suitable for the real-time monitoring of water vapor. Thus, this study clarifies the structure of water adsorbed on nanomaterial surfaces and, hence, the action mechanism of the corresponding nanoparticle-based sensors, inspiring further research on the application of various nanomaterials to vapor sensing. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) serves as extensively researched adsorbents, with numerous established methods for their preparation. This study originated from the hypothesis that compressing a hydrocarbon substance to create a densely compacted pellet, known as pelletizing, would enhance the development of porous features of the resulting AC. The anticipated enhancement is attributed to the rise in spatial proximity amidst HEC polymer chains within the bulk of the pellet, which facilitates aromatization both in extent and functionality. 2-Hydroxyethyl cellulose (HEC) pellets were prepared by adjusting the duration of load holding, aiming to increase the packing density of HEC polymer chains via creeping. The BET analysis of the resulting AC samples demonstrates the efficacy of compression on HEC pellets in enhancing their porous properties. The FE-SEM study revealed diverse AC surface morphologies that are associated with a set of specific pelletizing conditions. The 13C NMR spectroscopy for carbon skeletons, FT-IR spectroscopy for organic functionality, and XPS spectroscopy for surface composition collectively report the leverage of compression treatment before pyrolyzing HEC pellets. Furthermore, the assessment of hydrogen sulfide adsorption by the resulting AC samples revealed distinctive breakthrough curves, providing validation for the proposed compression effect.

There is a large amount of water in coal pores in the form of adsorption, which is referred to as adsorbed water. The adsorbed water can negatively affect gas adsorption and migration, thus affecting coalbed methane production and the geological storage of carbon dioxide in coal. Much research has been done to investigate the properties of adsorbed water using powder samples. However, it is still unclear how particle size influences water adsorption in coal. In this study, water adsorption experiments were carried out to examine the water adsorption characteristics of coal with different particle sizes. The modified Dent model and a kinetics model were utilized to interpret water adsorption in coal with varying maturity levels. It was found that smaller particle size leads to higher micropore volume and micropore surface area of samples, which could be the reason that smaller particles have higher water adsorption rates and water adsorption amounts. Besides, it was also found that the change in particle size has a weaker impact on the overall water adsorption amount of high-rank coal compared to that of low-rank coal. Therefore, water adsorption properties measured by particles may not be applicable to real coal blocks, especially for low-maturity coals. However, it was found that the change in particle size eventually leads to the same difference in the flow rate of different samples. This study deepens the understanding of water adsorption mechanism in coal with typical particle sizes. [ABSTRACT FROM AUTHOR]

To demonstrate a facile method to control capillary condensation via the design of confined geometric structures, we use a particle self-assembly technique to fabricate porous materials with well-defined pore sizes. Four groups of silica particles were synthesized using the modified Stober method, and these groups of particles were then arranged in closely packed structures. Quantitative predictions of capillary condensation were made based on the Kelvin equation and an approximation of the geometric structures of our closely packed samples. Experimental observations revealed that water uptake at 100% relative humidity reached 40%–50% relative to particle mass across sizes, closely aligning with theoretical predictions for small-particle systems, even though the geometry of some of the confined spaces corresponds to distances smaller than 10 nm. Despite deviation from theoretical predictions that are observed in larger particle systems, and which can be attributed primarily to practical limitations of attainable ordered structures at these scales, this fabrication method shows great potential for the creation of devices that allow facile control of capillary condensation in relevant applications such as vapor capture and humidity control.

We present a pore-scale simulation of the capillary condensation of water in the cathode catalyst layer (CCL) of proton exchange membrane fuel cells by the lattice Boltzmann method. Based on the reconstructed CCL, the capillary condensation process in CCL is simulated under different humidity conditions, and the effects of porosity and especially wettability on the liquid water distribution in CCL are studied. The influence of liquid water on the void pore size distribution and pore connectivity in CCL is evaluated, and the results show that the hydrophilic CCL is more prone to be flooded. Subsequently, the effective transport coefficients of oxygen and proton in partially saturated CCL are investigated. The results reveal that the hydrophobic CCL is beneficial for reducing the gas transport tortuosity but simultaneously causes a higher Knudsen diffusion resistance. By comprehensively considering the changes in tortuosity and Knudsen resistance caused by liquid water, a more practical correlation of effective diffusivity for the partially saturated CCL is proposed. Moreover, this work proves the vital role of liquid water in the proton conduction in CCL. The simulated effective proton conductivity in CCL is more agree with the measurements if the contribution of liquid water to proton transport is considered. [Display omitted] • Capillary condensation in the CCL is simulated at the pore scale. • A correlation of effective diffusivity to porosity and saturation is proposed. • Liquid water significantly increases the effective proton conductivity in the CCL. [ABSTRACT FROM AUTHOR]

Nanomaterial-based humidity sensors hold great promise for water vapor detection because of their high sensitivity and fast response/recovery. However, the condensation of water in nanomaterial films remains unclear from a physicochemical perspective. Herein, the condensation of water vapor in silica nanoparticle films was physicochemically analyzed to bridge the abovementioned gap. The morphology of surface-adsorbed water molecules was characterized using infrared absorption spectroscopy and soft X-ray absorption spectroscopy, and the effect of RH on the amount of adsorbed water was observed using a quartz crystal microbalance. The adsorbed water was found to exist in liquid- and ice-like states, which contributed to high and low conductivity, respectively. The large change in film impedance above 80% RH was ascribed to the condensation of water between the nanoparticles. Moreover, RH alteration resulted in a colorimetric change in the film’s interference fringe. The obtained insights were used to construct a portable device with response and recovery times suitable for the real-time monitoring of water vapor. Thus, this study clarifies the structure of water adsorbed on nanomaterial surfaces and, hence, the action mechanism of the corresponding nanoparticle-based sensors, inspiring further research on the application of various nanomaterials to vapor sensing.

We use results from grand canonical molecular dynamics (GCMD) to test the predictions from dynamic mean field theory (DMFT) for the pore filling and capillary condensation mechanisms of a fluid confined in slit shaped mesopores. The theory predicts that capillary condensation occurs by a nucleation process in which a liquid bridge forms between the two walls, and the pore is filled via the growth of this bridge. For longer pores, multiple bridging is seen. These mechanisms are confirmed by the molecular dynamics simulations. The primary difference between the theory and simulations lies in the role of fluctuations. DMFT predicts a single nucleation time and location, while in GCMD (and in nature) a distribution of nucleation times and locations is seen. [ABSTRACT FROM AUTHOR]

This paper investigates a novel fiber-based filter media wherein a NaCl filtrate is collected and reservoired not only onto the surfaces of the fibers and within their inter-fiber voidage but also within the internal porosity of high pore volume nanoporous fibers or vapor grown carbon nanofibers (VGCF) floc used to fabricate the media. This transport process is shown to occur through a NaCl dissolution into the water-filled nanopores of the fiber and a subsequent intra-fiber wicking phenomenon. The study further elucidates two distinct NaCl accommodation mechanisms which are uniquely available to filter media containing nanoporous intrafiber porosity: (1) wicking and capillary condensation of liquid NaCl aerosols directly into the intrafiber pores at high RH, and (2) dissolution of otherwise solid NaCl aerosols deposited onto fiber surfaces (at low RH) into the interior nanopores of the fiber because these pores (when hydrophilic) are saturated with water (even at low RH). To investigate these two mechanistic regimes, various media were fabricated possessing multiscale porosity in the form of: (i) embedded flocs of VGCFs (4.108 cm 3 gm -1 pore volume), (ii) hydrophilic and high pore volume activated carbon fibers (ACFs, 0.950 cm 3 gm -1 ) and (iii) solid graphite fibers. These media were then comparatively evaluated toward NaCl aerosol filtration at different relative humidities. Pressure drop measurements versus filtrate accumulation and SEM-EDAX VGCF demonstrated the location and transport of NaCl into the intrafiber voidage. Media containing both VGCF floc and ACF accumulated 1200% more NaCl at low RH (and a specified pressure drop) than similar media prepared from non-porous graphite fibers, with an additional 315% increase from low to high RH. A Gibbs free energy driving force model is provided to illustrate the driving forces favoring water condensation into the nanopores and solid NaCl aerosol dissolution into the water phase. Filtration efficiency and quality factor assessments for the various media are also systematically evaluated to demonstrate the observed mechanistics., (Creative Commons Attribution license.)

Humidity sensing has a wide application and receives intense attention from a broad spectrum of research areas. In this work, we demonstrated a robust humidity sensing strategy by loading photoacid HPTS (8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt) into nanopores of hollow mesoporous organosilica (HMO) capsules. Taking advantage of the capillary condensation of nanopores, water vapor is enriched, which triggers the fluorescent color change of HPTS through intermolecular excited-state proton transfer (ESPT) for humidity sensing. The ESPT induced fluorescent color change behavior of HPTS loaded in nanopores was comprehensively investigated by using both steady and picosecond time-resolved fluorescence spectroscopy. The fabricated humidity sensors exhibit rapid response and recovery, qualified reversibility, and selectivity, which enable continuous monitoring of human respiration. Notably, the sensing performance, i.e., sensitivity and response range, can be effectively tuned by fabricating HMO capsules with properly sized nanopores, which provides an opportunity to design unique nanostructures of the humidity sensor for specific applications. [ABSTRACT FROM AUTHOR]

This study provides evidence and mechanistic interpretations for the significant consequences of intrapore non‐polar liquids on acetone aldol condensation turnover rates, selectivity to primary dimer products, and catalyst stability for reactions at Lewis acid‐base site pairs on TiO2 surfaces. These non‐polar liquids confer such benefits through the preferential stabilization of transition states (TS) for adsorption ("entry") and desorption ("exit") steps, which place their respective reactants or products within a solvating outer sphere environment. The extent to which non‐polar fluids (n‐heptane) form an intrapore liquid phase within TiO2 voids was obtained from N2 uptakes using established formalisms that consider the different molal volume, surface tension, and volatility between N2 and n‐heptane. Acetone condensation rates are limited by C−H activation, an "entry" step that forms bound prop‐1‐en‐2‐olates via a TS stabilized by intrapore liquids, leading to higher aldol condensation turnover rates as n‐heptane pressure increases and active TiO2 surfaces become increasingly immersed within a non‐polar liquid phase. These liquids solvate the late TS structures that mediate the desorption of primary C6 condensation products even more effectively than those involved in prop‐1‐en‐2‐olate formation or in nucleophilic attack events that later form C−C bonds. Such preferential solvation favors desorption over C−C coupling events, thus disfavoring the formation of larger oligomers that become stranded at active sites, thus leading to much slower deactivation. Moreover, solvation by non‐polar liquids also leads to C6 alkanones as the sole products formed in a single surface sojourn. These effects of a non‐polar dense phase circumvent the inherent stability, reactivity, and selectivity hurdles that have precluded practical aldol condensation catalysis on Lewis acid‐base pairs at oxide surfaces; these consequences are demonstrated here for TiO2 catalysts, acetone aldol condensation reactions, and n‐heptane as the non‐polar liquid but through strategies, concepts, and mechanistic features that extend to other systems. More generally, these observations and their mechanistic origins demonstrate how a contacting liquid preferentially solvates TS structures for elementary steps that involve either reactants arriving from or products entering into an outer sphere environment that contains a dense non‐polar phase. [ABSTRACT FROM AUTHOR]

Water retention curve (WRC) is an important tool to study the hydraulic and mechanical properties of unsaturated soils, such as permeability, strength and deformation properties. Most of the existing WRC models fail to reflect the water retention mechanisms of unsaturated soils or they are complex in form, and these models are hard to give good performance on modelling the bimodal and multimodal WRCs. In this study, based on analyzing the water retention mechanisms of unsaturated soils, the WRC was divided into two domains that are governed by adsorption and capillary mechanisms, respectively. An adsorption water retention curve model (WRCM) was developed based on micro-pore filling theory and Kelvin’s law. A capillary WRCM was established based on the capillary condensation theory and Young-Laplace equation. Then, a new water retention curve model over the full suction range was built by superposing the adsorption and capillary WRCMs. Finally, the new model was validated through modelling the experimentally measured WRCs of six representative unsaturated soils, including Shanghai soft clay, Xi’an loess, Nanyang expansive soil, Guilin lateritic clay, Western Liaoning aeolian soil and Inner Mongolia Gaomiaozi (GMZ) bentonite. Results showed that the proposed model, which was simple in form with definite physical meaning parameters and successfully reflected the adsorption and capillary mechanisms of water retention, was able to simulate WRCs with different shapes for different types of soils under different conditions.

Using molecular simulation, we analyze the capillary condensation and evaporation processes for argon confined in a cylindrical nanopore. For this purpose, we define the entropy of the adsorbed fluid as a reaction coordinate and determine the free energy associated with both processes along entropic pathways. For capillary condensation, we identify a complex free energy profile resulting from the multi-stage nature of this phenomenon. We find capillary condensation to proceed through the nucleation of a liquid bridge across the nanopore, followed by its expansion throughout the pore to give rise to the stable phase of high density. In the case of capillary evaporation, the free energy profile along the entropy pathway also exhibits different regimes, corresponding to the initial destabilization of the layered structure of the fluid followed by the formation, and subsequent expansion, of a bubble across the nanopore. [ABSTRACT FROM AUTHOR]

The adsorption and condensation of water molecules in the pores of cementitious materials play a crucial role in the mechanical performance and durability of concrete. The Kelvin equation is generally employed to describe the water condensation in porous materials. However, it requires modification for condensation behavior in nano and micro scales of pores. In the present work, various widths of slit models for several cementitious minerals were established. The adsorption isotherms in slit pores were calculated using the hybrid of Grand Canonical Monte Carlo and Molecular Dynamics simulations, obtaining the relationship between the critical pressures for condensation and pore sizes. Then, a modified Kelvin equation was proposed, with discussion on a new reasonable method for determining the real thickness of adsorbed water film. The results demonstrate that condensation will occur in the slits within the critical width range, which promotes the surface adsorption to achieve complete adsorption. Therefore, the location of the interface between the adsorbed water film and condensed water bulk is fixed in the same mineral during condensation. The modified Kelvin equation shows higher accuracy than traditional Kelvin equations at the nano and micro scale. This work promotes a deeper understanding of the interaction mechanism of water with cementitious minerals and inspires more fundamental realization in the design of concrete durability. • Water adsorption and condensation in CSH slits are calculated by GCMC simulations. • Water condenstion induced complete adsorption was firstly found. • The interface location between adsorbed layer and condensed bulk is determined. • The Kelvin equation is refined to describe condensation in micropores of CSH. [ABSTRACT FROM AUTHOR]

Adsorption equations are important to analyze the pore size distribution (PSD) of shale and the adsorption behavior on it. However, the accurate description of nitrogen adsorption on shale by current adsorption equations is difficult to achieve due to the heterogeneous pore structure of shale. In our study, new adsorption isotherms that can properly depict the adsorbed amount of nitrogen were built for shale rocks considering both the processes of nitrogen adsorption and the cylindrical pore shape property of shale. When performing a regression analysis on five sets of experimental adsorption data using the developed adsorption equations, the R-square ranged from 0.739 to 0.987. Based on the pore shape determined by adsorption–desorption curves, the distinct R-square indicated that our equation is not valid for shale samples with ink-bottle pores and pores formed by schistose materials, but that it is suitable for shale samples with cylindrical pores and slit pores. Meanwhile, we precisely analyzed the PSDs of shale rocks based on the developed adsorption equations as capillary condensation volume is involved in the total adsorbed amount. Thus, the PSDs of shale rocks with cylindrical pore and slit pore were analyzed by the new adsorption equation. [ABSTRACT FROM AUTHOR]

Nanotechnology drives technological progress in many frontiers, from electronics to medicine, from tougher composites to adaptive surfaces. As the feature sizes are made smaller, the importance of surfaces is increased. Many of the most powerful methods for surface manipulation are variants of vapor deposition (VD). However, VD is typically not surface‐selective and, therefore, extra work steps are needed to integrate the methods into nanofabrication routines. Furthermore, many fields are moving toward 3D nanostructures, which unavoidably means increasingly complex nanocavities. Capillary condensation (CC) offers new selectivity rules for VD by inherently targeting cavities, which have been the most difficult locations to coat thus far. The most important controlling parameter in CC is the partial pressure, which is primarily adjusted by the reaction chamber, not the substrates or the reagents. In this article, the theory of CC, different reactor setups, materials, reagents and substrates, and various applications of CC in VD techniques are presented. The CC‐based methods are briefly compared to other cavity‐filling methods for gaining perspective on their potential for advancing modern technology. Finally, several observations on the characteristics of the methods, termed collectively as condensation‐controlled toposelective vapor deposition, are analyzed. The implications may affect the way one thinks about VD. [ABSTRACT FROM AUTHOR]

The separation of H 2 O vapor from (hydrogen-rich) gaseous streams is a topic of increasing interest in the context of CO 2 valorisation, where the in situ water removal increases product yield and catalyst stability. In this work, composite alumina carbon molecular sieve membranes (Al-CMSM) were prepared from phenolic resin solutions loaded with hydrophilic boehmite (γ-AlO(OH)) nanosheets (0.4–1.4 wt. % in solution) which partially transform to γ-Al 2 O 3 nanosheets upon thermal decomposition of the resin, improving the hydrophilicity and thus the adsorption-diffusion contribution of the H 2 O permeation. The γ-Al 2 O 3 nanosheets showed no influence on the pore size distribution of the membranes in the range of micropores, but they increased the membrane hydrophilicity. In addition, the use of boehmite in the resin solution causes an increase in the viscosity and thus an increase in the carbon layers thickness deposited on the porous α-Al 2 O 3 support (from 1 to 3.3 μm). Furthermore, the alumina sheets introduce defects in the carbon matrix, increasing the tortuosity of the active layer, as concluded via phenomenological modelling and parametric fitting of the experimental results. As a consequence, the water permeability exhibits a maximum (1.3ꞏ10−6 molꞏs−1 Pa−1 m−1 at 150 °C) with boehmite/alumina content of ca. 0.8 wt. %, as the combined effects of increasing hydrophilicity (which favour H 2 O permeability) and increasing thickness and tortuosity (which hamper permeability) upon increasing boehmite loading. Similarly, the H 2 O/gas perm-selectivity is optimum at 1.2 wt. % boehmite loading. We further investigated the H 2 O permeation mechanism by modelling the mono- and multi-layer adsorption and capillary condensation of water in microporous media, which result as the main transport mechanisms in the explored conditions. • Several boehmite-phenolic resin composite carbon molecular sieve membranes were developed. • The hydrophilic boehmite nanosheets were used to increase the adsorption of water. • Water permeability shows an optimum with the initial boehmite content around 0.8 wt. %. • CMSM are promising material for the water separation from gaseous mixtures at relatively high temperatures. [ABSTRACT FROM AUTHOR]

A liquid-dependent impedance is observed by vapor condensation and percolation in the void space between nanoparticles. Under the Laplace pressure, vapor is effectively condensed into liquid to fill the nanoscale voids in an as-deposited nanoparticle film. Specifically, the transient impedance of the nanoparticle film in organic vapor is dependent on the vapor pressure and the conductivity of the condensed liquid. The response follows a power law that can be explained by the classical percolation theory. The condensed vapor gradually percolates into the void space among nanoparticles. A schematic is proposed to describe the vapor condensation and percolation dynamics among the nanoparticles. These findings offer insights into the behavior of vapor adsorbates in nanomaterial assemblies that contain void space. [ABSTRACT FROM AUTHOR]

• Ceramic tiles with humidity self-regulation functionality can be prepared from compositions with gibbsite. • Compositions with gibbsite generate microstructures with presence of mesopores which are responsible for humidity regulation. • The adsorption and desorption curves fit a pseudo-second order model. The development of ceramic tiles with humidity regulating capacity is a topic of great interest for the comfort of interior spaces. The humidity regulating capacity of fired specimens from five compositions used for porous ceramic products has been assessed and their microstructure has been characterised. The main novelty of the work consists of obtaining pieces with regulating functionality from common ceramic raw materials used in industrial practice, establishing a kinetic model and confirming the role of porosity and microstructure. The results have shown that moisture adsorption and desorption curves fit very well to a pseudo-second order model. Additionally, it has been found that the humidity regulating capacity is not related to the total porosity, but it depends on the presence of mesopores in the structure of the pieces. Concerning the tested compositions, those containing gibbsite present higher regulating capacity as a consequence of their greater amount of mesopores. [ABSTRACT FROM AUTHOR]

Ni cation sites exchanged onto microporous materials catalyze ethene oligomerization to butenes and heavier oligomers but also undergo rapid deactivation. The use of mesoporous supports has been reported previously to alleviate deactivation in regimes of high ethene pressures and low temperatures that cause capillary condensation of ethene within mesoporous voids. Here, we reproduce these prior findings on mesoporous Ni‐MCM‐41 and report that, in sharp contrast, reaction conditions that nominally correspond to ethene capillary condensation in microporous Ni‐Beta or Ni‐FAU zeolites do not mitigate deactivation, likely because confinement within microporous voids restricts the formation of condensed phases of ethene that are effective at solvating and desorbing heavier intermediates that are precursors to deactivation. Deactivation rates are found to transition from a first‐order to a second‐order dependence on Ni site density in Ni‐FAU zeolites with increasing ethene pressure, suggesting a transition in the dominant deactivation mechanism involving a single Ni site to one involving two Ni sites, reminiscent of the effects of increasing H2 pressure on changing the kinetic order of deactivation in our prior work on Ni‐Beta zeolites. [ABSTRACT FROM AUTHOR]

Purification of gases by membranes can provide enormous energy savings. Inorganic membranes offer good stability and regenerability, but large margin manufacturing is limited. Silica membranes are an exception since they can be produced by coating with molecular precursors. However, such membranes do not have a defined pore structure, which limits their applicability in mass separation. Nevertheless, it is possible to fill the pores of silica membranes with condensate of a component to be separated from gas mixtures. In this work, this applicability of a micro‐mesoporous silica membrane was demonstrated exemplarily by the separation of n‐butane (C4) from mixtures containing methane (C1). The main result, which was supported by grand canonical Monte Carlo (GCMC) simulations, is that capillary condensation contributes significantly to the performance. The experimental results showed that the n‐butane separation efficiency (permeate flux and separation selectivity) through the silica membrane under the condensation conditions is excellent and thus can serve as a model for similar separation tasks. [ABSTRACT FROM AUTHOR]

Capillary condensation in the regime of developing hysteresis occurs at a vapor pressure, Pcond, that is less than that of the vapor-like spinodal. This is because the energy barrier for the vapor-liquid transition from a metastable state at Pcond becomes equal to the energy fluctuation of the system; however, a detailed mechanism of the spontaneous transition has not been acquired even through extensive experimental and simulation studies. We therefore construct accurate atomistic silica mesopore models for MCM-41 and perform molecular simulations (gauge cell Monte Carlo and grand canonical Monte Carlo) for argon adsorption on the models at subcritical temperatures. A careful comparison between the simulation and experiment reveals that the energy barrier for the capillary condensation has a critical dimensionless value, Wc* = 0.175, which corresponds to the thermal fluctuation of the system and depends neither on the mesopore size nor on the temperature. We show that the critical energy barrierWc * controls the capillary condensation pressure Pcond and also determines a boundary between the reversible condensation/evaporation regime and the developing hysteresis regime. [ABSTRACT FROM AUTHOR]

The nitrogen sorption isotherm is conventionally used to deduce the specific surface area of porous materials. However, it often exhibits a sharp drop around 0.5 relative pressure. A theory explicitly accounting for intermolecular-scale pressure, instead of classical theories of constant disjoining pressure in condensed liquid, is constructed and used to determine cavitation during desorption. Intermolecular-scale liquid pressure distribution is quantified using a recently developed soil sorptive potential framework, showing compressive liquid nitrogen pressure decaying nonlinearly with increasing distance to the particle surface. A range of cavitation pressure is predicted by classical nucleation theory and the van der Waals equation of state. Cavitation is shown to be triggered when nitrogen's global minimum liquid pressure falls within the cavitation threshold. It is shown that this criterion is valid for all tested soils. Computed minimum liquid pressure always occurs at 0.5 relative pressure, which is in accordance with experimental isotherm data and further indicates the validity of the cavitation onset criterion. [ABSTRACT FROM AUTHOR]

The scanning hysteresis loop provides information about the correlation of the pore network, its connectivity and pore size distribution; nonetheless, this correlation cannot be revealed from the complete isotherm. To analyze the connectivity of the porous network in ordered mesoporous materials modified with iron and cobalt oxides, Ar adsorption–desorption isotherms and their corresponding scanning of the hysteresis loops at three temperatures (65, 77, and 87 K) were measured. Two mathematical models based on the independent domains theory (i.e. Uncorrelated Model (UM) and Partial Correlated Model (PCM)) were applied to adjust the desorption branches in the hysteresis loops associating these results to the connectivity in the porous network and the presence of pore-blocking effects. [ABSTRACT FROM AUTHOR]

In this paper we consider the main application features of the thermal desorption method of inert gases, implemented on the Sorbi MS (Meta, Russia) device, for the analysis of meso- and microporous materials. Recommendations on the choice of measurement modes for stable operation of the Sorbi MS device are offered (including recommendations on mass, sample preparation mode). The article presents the results of the micropores analysis by the t-plot and Sing method.

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A novel composite material composed of carbon-quantum-dots@nanofiber clusters (CQDs@NFCs) is successfully developed in wafer level, taking it as a sensitive material, a flexible humidity sensor is also developed. Since the composite material is superhydrophilic and contains a super large number of nanopores of different sizes, capillary condensation is able to take place within the composite material at different relative humidity (RH) conditions. Taking advantage of the chemi-physisorption and the capillary condensation, such a sensing material helps to significantly improve sensitivity of the flexible sensor, especially at low RH conditions. Compared with the device adopting only nanofibers as the sensing material, this novel sensor offers a 4.3-time increament in sensitivity within a humidity range of 7%−59% RH, while maintains high sensitivity in the entire humidity range. This heightened sensitivity is crucial for monitoring low-level humidity with high accuracy, making the sensor highly promising for various applications. • CQDs@NFCs, a novel composite, is made via wafer-level plasma etching and solvent evaporation. • The composite material CQDs@NFCs exhibit a large surface area and a significant number of hydrophilic groups. • CQDs@NFCs are used in flexible humidity sensors with high sensitivity and a broad range. • The flexible humidity sensor offers potential for diverse applications, aiding smart electronics development. [ABSTRACT FROM AUTHOR]

Steam adsorption enhanced reaction processes are a promising process intensification for many types of reactions, where water is formed as a byproduct. To assess the potential of these processes, adequate models are required that accurately describe water adsorption, particularly under the desired elevated temperatures and pressures. In this work, an adsorption isotherm is presented for H2O adsorption at 200–350 °C and 0.05–4.5 bar partial pressure on molecular sieve (LTA) 3A. The isotherm has been developed on the basis of experimental data obtained from a thermogravimetric analysis and integrated breakthrough curves. The experimental data at lower steam partial pressures can be described with a Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm, whereas at higher steam partial pressures the experimental data can be adequately captured by capillary condensation. Based on the characteristics of the adsorbent particles, a linear driving force relation has been derived for the adsorption mass transfer rate and the apparent micropore diffusivity is determined. The isotherm and mass transport model presented here prove to be adequate for modelling and improved evaluation of steam adsorption enhanced reaction processes. [ABSTRACT FROM AUTHOR]

Fluids adsorbing in nanoporous solids cause high solvation pressures that deform the solids and affect properties of the fluids themselves. We calculate solvation pressure of nitrogen adsorbed at 77.4 K in spherical silica mesopores using two methods: the macroscopic Derjaguin–Broekhoff–de Boer theory and molecular simulations. We show that both approaches give consistent results, and the observed pressures increase in smaller pores reaching the order of a hundred megapascals. The results are also typical for the solvation pressure in mesoporous materials, yet noticeably differ from the results for the cylindrical pore geometry. Furthermore, we show that the dependence of the solvation pressure at saturation on the reciprocal pore size is linear, and we use this relation for the calculation of the solid–liquid surface energy. The results can be employed for the prediction of the solvation pressure and the adsorption‐induced deformation in the material with the spherical pore geometry. [ABSTRACT FROM AUTHOR]

Adsorption equations are important to analyze the pore size distribution (PSD) of shale and the adsorption behavior on it. However, the accurate description of nitrogen adsorption on shale by current adsorption equations is difficult to achieve due to the heterogeneous pore structure of shale. In our study, new adsorption isotherms that can properly depict the adsorbed amount of nitrogen were built for shale rocks considering both the processes of nitrogen adsorption and the cylindrical pore shape property of shale. When performing a regression analysis on five sets of experimental adsorption data using the developed adsorption equations, the R-square ranged from 0.739 to 0.987. Based on the pore shape determined by adsorption–desorption curves, the distinct R-square indicated that our equation is not valid for shale samples with ink-bottle pores and pores formed by schistose materials, but that it is suitable for shale samples with cylindrical pores and slit pores. Meanwhile, we precisely analyzed the PSDs of shale rocks based on the developed adsorption equations as capillary condensation volume is involved in the total adsorbed amount. Thus, the PSDs of shale rocks with cylindrical pore and slit pore were analyzed by the new adsorption equation.

Recent experiments have revealed that the macroscopic Kelvin equation remains surprisingly accurate even for nanoscale capillaries. This phenomenon was so far explained by the oscillatory behavior of the solid-liquid interfacial free energy. We here demonstrate thermodynamic and capillarity inconsistencies with this explanation. After revising the Kelvin equation, we ascribe its validity at nanoscale confinement to the effect of disjoining pressure. To substantiate our hypothesis, we employed molecular dynamics simulations to evaluate interfacial heat transfer and wetting properties. Our assessments unveil a breakdown in a previously established proportionality between the work of adhesion and the Kapitza conductance at capillary heights below 1.3 nm, where the dominance of the work of adhesion shifts primarily from energy to entropy. Alternatively, the peak density of the initial water layer can effectively probe the work of adhesion. Unlike under bulk conditions, high confinement renders the work of adhesion entropically unfavorable.

Water condensation in shales impacts its hydro-mechanical response. A mechanistic understanding of the pore-water system is made more challenging by significant anisotropy of pore architecture and nano-scale heterogeneity of pore surfaces. We probe the condensation response in two contrasting shales exposed to a vapor of contrast-matching water, as characterized by in situ ultra-small/small-angle neutron scattering (USANS/SANS) techniques under various relative humidities. One shale with a higher content of both kerogen and clay has rougher surfaces and higher anisotropy than the other shale (less clay and no kerogen) over length scales from 2.5 to 250 nm. Scanning electron microscopy with energy-dispersive spectrometry (SEM–EDS) analysis also confirms that the organic-rich shale presents more anisotropic microfabrics and higher heterogeneity compared to the other shale with less clay and no kerogen. USANS/SANS results show that water condensation effectively narrows the pore volume in the way of reducing the aspect ratio of non-equiaxed pores. For the shale with less clays and no kerogen under a relative humidity of 83%, a wetting film uniformly covers the pore-matrix interface over a wide range of length scale (1 nm–1.9 µm) without smoothing the surface roughness. In contrast, for the organic-rich and clay-rich shale with a strong wetting heterogeneity, condensation occurs at strongly curved hydrophilic asperities (1–10 nm) and smoothens the surface roughness. This is consistent with water vapor condensation behavior in a Vosges sandstone by Broseta et al. (Phys. Rev. Lett. 86:5313, 2001). Though well representing the condensation behavior of water vapor in mesopores/macropores (radii > 1 nm), USANS/SANS techniques could underestimate total water adsorption due to potential cation hydration and clay swelling in micropores (radii < 1 nm). [ABSTRACT FROM AUTHOR]

Surfaces that entrap air underwater serve numerous practical applications, such as mitigating cavitation erosion and reducing frictional drag. These surfaces typically rely on perfluorinated coatings. However, the non‐biodegradability and fragility of the coatings limit practical applications. Thus, coating‐free, sustainable, and robust approaches are desirable. Recently, a microtexture comprising doubly reentrant cavities (DRCs) has been demonstrated to entrap air on immersion in wetting liquids. While this is a promising approach, insights into the effects of surface chemistry, hydrostatic pressure, and cavity dimensions on wetting transitions in DRCs remain unavailable. In response, Cassie‐to‐Wenzel transitions into circular DRCs submerged in water are investigated and compared with those in cylindrical "simple" cavities (SCs). It is found that at low hydrostatic pressures (≈50 Pa), DRCs with hydrophilic (θo ≈ 40°) and hydrophobic (θo ≈ 112°) make‐ups fill within 105 and 107 s, respectively, while SCs with hydrophilic make‐up fill within <10−2 s. Under elevated hydrostatic pressure (P ≤ 90 kPa), counterintuitively, DRCs with hydrophobic make‐up fill dramatically faster than the commensurate SCs. This comprehensive report should provide a rational framework for harnessing microtexturing and surface chemistry toward coating‐free liquid repellency. [ABSTRACT FROM AUTHOR]

This paper presents a multi-scale modelling approach to describe the mechanical behaviour of caked powders as an aid to properly design and analyse the results of laboratory caking tests to assess the propensity of powders to cake. This approach is based on the integration of particle-particle interactions due to liquid or solid bridges over the total volume of a cake using Discrete Element Method (DEM). The overall objective of the study was to simulate the behaviour of agglomerated (caked) samples subjected to a mechanical, compressive or tractive, stress. First, simulations were performed on an assembly of particles subjected to capillary forces. The capillary forces being amenable to a theoretical description, the tensile strength of wet agglomerates was calculated theoretically and used as a reference to validate the numerical results. Simulations were based on the combination of conventional DEM method and the phenomenological model of capillary condensation. The stress-strain curves were then simulated and compared to the theoretical values predicted by Rumpf's model for wet agglomerates. After validation, numerical simulations were used to study the mechanical behaviour of wet or dry agglomerates subjected to compression. In order to take into account the cohesive effect of solid bridges at the level of elementary contacts in discrete modelling, an original Euler-Bernoulli type beam model between particles in contact was established. The simulated stress-strain results was in very good agreement with experimental data. • DEM simulations were successfully performed to describe the behaviour of wet cakes. • Mechanical strength of dry cakes were simulated using a DEM-beam model. • The beam model is a promising method for simulation of dry cakes strength. [ABSTRACT FROM AUTHOR]

Consequences of water vapor condensation were studied in natural gas dehydration using 4A zeolite. Adsorption-desorption isotherms were studied experimentally and isotherm parameters were predicted using two-site Sips model with maximum 9.6% deviation. Water vapor diffusivity within the adsorbent pores was evaluated and modified by predicting the pore filling pattern. The dehumidification process was modeled employing two assumptions, in the first case, water vapor was assumed to condense within the particles and in the second case no condensation was taken place. After comparison, it was resulted that in the first case, 12% less vapor was absorbed in the bed and 14% more vapor remained inside the adsorbent pores after regeneration. [ABSTRACT FROM AUTHOR]

In order to study the characteristics of carbon nanotubes, a series of N2 at 77.4 K adsorption experiment were carried out in the laboratory, and the adsorption isotherms of different types of carbon nanotubes (CNTs) were obtained. The micropore and mesopore size distributions of CNTs were determined using the modified Horvath-Kawazoe and BJH models based on the adsorption-desorption isotherms. And the adsorption capacities of CNTs in different adsorption stages, such as the micropore volume filling stage, multi-layer adsorption stage and capillary condensation stage, were evaluated based on the adsorption isotherms. The results show that the maximum pore size of CNTs corresponding to the pore volume filling is about 9 nm. The amount of N2 adsorbed in the tube of CNTs is negative with the pore size. However, the amount of N2 in the status of capillary condensation is positive with the pore size of CNTs. [ABSTRACT FROM AUTHOR]

Temperature is an important factor influencing gas content in coal seam. The adsorbed layer thickness in coal has not been quantitatively analyzed under different temperatures. To probe the temperature evolvement and its effect on methane adsorbed layer thickness in coal, the adsorbed layer thickness equation is established based on thermodynamic principles. The adsorbed layer thickness increases with decreasing temperature and increasing equilibrium pressure. The low temperature can promote methane adsorption and increase the number of adsorbed layers. When the pore size is larger than the pore radius at which capillary condensation occurs, the adsorbed layer thickness will decrease as the pore radius increases. This phenomenon shows a negative exponential function. If the pore radius increases to a certain extent, the number of adsorbed layers does not change with the increasing pore radius. The number of adsorbed layers in the micropores and mesopores are greater than that in the macropores. The adsorbed methane quantity can be calculated by the pore size distribution function and adsorbed layer thickness function under different temperatures. The adsorbed layer thickness theory not only reveals the mechanism of temperature influencing methane adsorption in coal but also can be used to predict the adsorption isotherms at different temperatures and pressures if the pore size distribution is known. [ABSTRACT FROM AUTHOR]

Transport membrane condenser is a water heat recovery technology based on condensation mechanism. Limited by the price of ceramic membrane, it focuses on enhancing the heat and mass transfer technology of ceramic membrane. Acoustic enhancement of heat and mass transfer is an efficient enhancement method. In order to explore the heat and mass transfer characteristics of ceramic membrane enhanced by audible sound field under different condensation mechanisms, the corresponding experimental platform was built. The results show that due to the condensation characteristics of capillary condensation, the heat and mass transfer performance of the nano membrane under the action of sound field is greatly improved, with a maximum increase of 53.44% and 53.22%, respectively; This article presents an analysis of the economic advantages of utilizing acoustic waves in conjunction with ceramic membranes. It is found that the recovery period can be shortened by 3.2 years when acoustic waves are employed. The findings of this study offer a valuable foundation for improving heat and mass transfer in flue gas moisture recovery systems utilizing ceramic membranes. • Investigation of optimization and selection of wide frequency sound field. • Condensation mechanism determines the degree of sound field enhancement. • Study on heat and mass transfer mechanism in Porous medium under sound field. • Initial technical and economic research was conducted using membrane components. • Optimizing TMC performance under new working conditions. [ABSTRACT FROM AUTHOR]

It has been customary to describe the phase equilibria of confined fluids using an equation of state (EOS) coupled with the Young-Laplace equation to account for the effect of surface curvature due to confinement. The equilibrium phases in this approach are the vapor (V) in the bulk phase and the confined liquid-like phase (ℓ) in the pores, which are separated by a surface that introduces a pressure difference between the phases. Consequently, we refer to this approach as the Vℓ method. The condition of phase transitions for confined fluids has been assumed to be the same as that for bulk fluids, so that calculations for dew-point and bubble-point curves do not need a material balance because the mole fraction of the condensed phase is zero for the former and unity for the latter. However, the situation of confined fluids is different from that in the bulk because the equilibrium phases reside in separate regions that have different pressures. In the Vℓ method, the vapor phase resides in the bulk and drives the chemical potential of the whole system, while the liquid-like phase condenses inside the pores subject to strong interaction with the pore wall. As discussed in the paper, this situation needs a material balance to comprehensively describe the phase transitions. Supporting evidence is also presented from a static experiment using a gravimetric apparatus. New insights derived from generalization of the Vℓ method in this work enable further investigations that could disclose more unknowns in the phase behavior of confined mixtures. [ABSTRACT FROM AUTHOR]

The corresponding state behaviour of capillary condensation of confined alkanes is studied by means of GC-TMMC simulations. In this study, alkane is considered under graphite and mica slit pore confinements of various slit widths. Corresponding state phase coexistence envelopes of capillary condensation display insignificant effect of surface chemistry for slit pore confinements of 6 Å for methane and 15 Å for n-butane and n-octane. On the other hand, the significant effect of surface chemistry on the corresponding state coexistence envelope is observed for larger slit pore width. Moreover, at a given slit width, more shrinking in the corresponding state coexistence envelope of alkane is observed with the mica slit pore as compared to graphite slit pore. The local behaviour of capillary condensation of corresponding state is also investigated in some typical cases using local density profiles, to understand the overall behaviour of corresponding state capillary condensation. Moreover, for a given slit pore width smaller size alkane has shown more shrinking of the corresponding state coexistence envelope, irrespective of surface chemistry. However, the effect of surface chemistry on the corresponding state coexistence envelope of different alkanes becomes insignificant in smaller slit pore width. Fluctuating positive and negative deviations in the corresponding state vapour–liquid equilibrium pressure with respect to corresponding bulk values are observed in studied slit pore confinements. The corresponding state vapour−liquid interfacial tension of alkanes is less in mica slit pore as compared to graphite slit pore for the studied range of reduced temperatures. [ABSTRACT FROM AUTHOR]

• Polymer/fiber composite membrane was presented for gas separation. • Capillary condensation mechanism occurred for CO 2 transport in polymer/fiber interface. • Composite membranes showed simultaneous enhancements in CO 2 permeability and CO 2 /CH 4 ideal selectivity. One of the most important shortcomings of the polymeric membranes in comparison with inorganic membranes is the trade-off between permeability and selectivity. Gas permeability in inorganic membranes follows different mechanisms including capillary condensation mechanism. The aim of present study was improving the polymeric membranes performance by introducing capillary condensation mechanism for the gas transport similar to that observed in the inorganic membranes. Capillary condensation of gases needs a continuous diffusion pathway, therefore in the present study short glass wool fibers (with a micro size in diameter and millimeter size in length) were chosen as a proper alternative instead of nanoparticles. Short glass wool fibers present proper dispersion in the Pebax matrix as a result of its good compatibility with polymer segments. Gas permeability behavior in such composite membranes was assisted using pure CO 2 , CH 4 and N 2 gases. Obtained results demonstrated that gas permeability behavior in the short fiber reinforced composite membranes is depends on the fiber content. At lower content of the fiber, such reinforcement causes simultaneous increment in gas permeabilities in a way that 62.37%, 32.12% and 50.71% increase in permeability was observed for CO 2 , CH 4 , and N 2 respectively. But at higher content due to formation of more continuous interface, capillary condensation was appeared for more condensable gas (CO 2) which results in 17.65% reduction in its permeability. Based on the results the using of short fiber instead of nanoparticles in polymeric membranes can be more beneficial in performance and economic point of view. [ABSTRACT FROM AUTHOR]

For the characterization of porous structures, besides the specific surface area, the pore size distribution is of special interest. In this paper, the pore size distribution of mesoporous structures is calculated from the adsorption branch of the hysteresis loop, whereby only loops of type H1 are considered. The modeling is done only for cylindrical capillaries and the calculation of the pore size distribution is done by a combination of the percolation theory and the theory of capillary condensation. By applying percolation theory to the adsorption process, the pressure dependence of pore filling during capillary condensation is described. Because of a lack of strictly theoretically based equations for the adsorption process by capillary condensation, a mathematical adaptation to measured data is done by the Bernoulli equation. This is proposed by the authors for the first time for a description of adsorption–desorption processes. Thus a new, strictly thermodynamic method to calculate the mesopore size distribution is gained. As an example, the pore size distribution is calculated. The results coincide well with other evaluation methods. [ABSTRACT FROM AUTHOR]