Capillary Condensation Research Articles

Eco-friendly high microporosity low temperature plasma exposed activated carbon from coconut shell for nano hybrid supercapacitors

Abstract This study looked at the structural, chemical, and electrochemical properties of coconut shell activated carbon (CSAC) before and after plasma treatment. Structural analysis using x-ray diffraction (XRD) demonstrated that plasma treatment improves graphitic structure by plans at (002) and (101) for higher angles. Chemical investigation utilizing Fourier-transform infrared spectroscopy (FTIR) revealed an increase in hydroxyl groups and carboxylic content following plasma treatment, which enhances electrochemical performance. Raman spectroscopy revealed a drop in the ID/IG ratio from 1.00 to 0.90, indicating enhanced graphitic order. Scanning electron microscopy (FESEM) showed that plasma treatment improves surface shape, while elemental analysis assessed the high carbon content (76.56% by weight). Contact angle measurements showed a decrease from 114° to 65°, showing improved hydrophilicity after treatment. Electrochemical investigation shows that the plasma-treated CSAC had a maximum specific capacitance of 1612 F g−1, compared to 729 F g−1 for the untreated CSAC, and a total capacitance of plasma treated1685 F/g are untreated 1400 F g−1. A Type II+III pattern on the isotherms implied capillary condensation in mesopores. The plasma treatment indicated improved porosity and potential adsorption capacity by increasing the specific surface area and decreasing the average pore width. The cyclic stability tests indicated that the plasma-treated CSAC retained 94% capacitance and 98% coulombic efficiency after 3000 cycles, which is superior to the untreated CSAC’s 92% capacitance retention and 95% coulombic efficiency. This reveals that plasma-treated CSAC has significantly improved performance and stability, making it an excellent alternative for high-performance and cost-effective energy storage applications.

The Effect of Wettability on Confinement-Induced Phase Behavior and Storage of Alkane in Nanoporous Media.

The impact of wettability on the confined phase behavior of fluids is paramount for various applications, such as gas storage, carbon dioxide sequestration, and water purification. However, the understanding of the fluid-solid intermolecular interactions in confined systems is still limited and requires further investigation. This work investigates the effect of hydrophilic and hydrophobic nanoporous materials on the adsorption and desorption isotherms of n-butane. The hydrophilic samples in this research are MCM-41 silica powder with two different pore sizes (80 and 100 Å). MCM-41 samples were successfully treated with hexamethyldisilazane (HMDS) to create hydrophobic adsorbents. Isotherms of n-butane in materials with different wetting states were generated at various temperatures using an upgraded gravimetric apparatus. The results demonstrated that n-butane was adsorbed more onto the hydrophilic MCM-41 materials during the initial adsorption process. The lower affinity between n-butane and the modified MCM-41 samples slightly increased the capillary condensation and evaporation pressures in these materials compared to those in the original ones. However, it is noted that wettability's influence on the confined phase transitions of n-butane was not significant in this study. Interestingly, the hysteresis behavior of the vapor-liquid and liquid-vapor phase transitions due to confinement was independent of the surface's wetting properties. Kelvin's equation for a hemispherical meniscus was adopted to evaluate the capillary evaporation pressures of n-butane in nanopores. The calculated pressures showed agreement with experimental data when appropriate pore size and surface tension values were applied. These findings provide valuable insights into the impacts of surface chemistry and wettability on the phase behavior of hydrocarbon gas in nanoporous media. Furthermore, this study enriches the experimental database on confined fluids, which is essential for developing accurate theoretical and modeling tools for numerous industrial and scientific applications.

Estimating cation exchange capacity from hygroscopic water content change

AbstractThe existing models for estimating cation exchange capacity (CEC) from easy‐to‐measure hygroscopic water content (θh) were based on a single water activity (aw) value rather than on the processes that govern soil water vapor adsorption for a distinct aw range. Here, we present a new CEC estimation model based on θh data of 119 soils with different clay mineralogy (i.e., illitic [IL], montmorillonitic [ML], and kaolinitic [KA] samples) and organic carbon (OC) contents for the aw range from 0.23 to 0.57 (Δθ0.23–0.57) and validate its performance. Based on the hypothesis that multilayer adsorption exhibits a higher correlation with CEC than monolayer adsorption and capillary condensation, the aw range from 0.23 to 0.57 was chosen with CEC calculated as CEC = k × Δθ0.23–0.57. The performance of the new model is compared to the Arthur (2017) model and the Torrent (2015) model, which considers a single θh value. The average proportionality coefficient (k) varied with the dominant clay mineralogy of the investigated soils. For soils dominated by 2:1 clay minerals (i.e., IL and ML), the new model showed a good estimation accuracy (Nash‐Sutcliffe model efficiency [E] ≥ 0.85; root mean squared error [RMSE] ≤ 4.18 cmol(+) kg−1). The new model performed better for IL and ML samples than for KA samples, and yielded more accurate CEC estimations than the Arthur model and Torrent model for soils with 2:1 clay minerals. For soil with high OC content (>23.2 g kg−1), the new model slightly underestimated CEC (E = 0.66; RMSE = 5.87).

D-BJH: The Intrinsic Model for Characterizing the Pore Size Distribution of Porous Materials.

A novel approach, the differential Barrett-Joyner-Halenda model (D-BJH), is proposed to address the limitations of the traditional BJH model in determining the pore size distribution (PSD). This method integrates multilayer adsorption and capillary condensation processes using advanced numerical techniques, notably, a Galerkin-based framework for solving the differential BJH equations. The D-BJH model offers a precise analytical framework, establishing itself as a benchmark in adsorption theory. It enables accurate PSD calculations and provides robust theoretical support for interpreting adsorption isotherms. Additionally, a simplified D-BJH method allows for direct point-by-point PSD calculation, reducing computational complexity and eliminating cumulative errors inherent in traditional methods like BJH, DH, CI, and VBS. The D-BJH model demonstrates that PSD is directly related to the differential function of the isotherm and pore size concerning relative pressure. Comparative analyses with BJH, DH, and NLDFT models show that D-BJH effectively explains fundamental adsorption mechanisms, such as the "spurious peak" observed in desorption branches. This work expands the applicability of the BJH model, proving that both the D-BJH model and its simplified method are accurate and comprehensive for characterizing the pore structures of microporous and mesoporous materials.

NaCl aerosol filtration over filter media with intrafiber porosity: can filtrate capacity be increased by wicking into this pore volume?

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 cm3gm-1pore volume), (ii) hydrophilic and high pore volume activated carbon fibers (ACFs, 0.950 cm3gm-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.

Comparative study of two mesoporous magnetic and MCM-41 supported Cu complex: High-performance heterogeneous catalysts for aqueous synthesis of tetrazole

The effects of the carrier were studied in the synthesis of tetrazole. Copper catalysts supported on CoFe2O4 and MCM-41 with serine ligands were prepared. Two mesoporous catalysts, CoFe2O4/Ser/Cu and MCM-41/Ser/Cu, (denote Serine with (Ser)) were synthesized and compared the activity of these catalysts in converting nitrile to tetrazole. The prepared material was characterized using powder X-ray diffraction (XRD),field emission scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDS), elemental mapping, vibrating-sample magnetometer (VSM), and nitrogen adsorption–desorption isotherm. The relation between the textural properties of the catalysts and the catalytic performance was investigated. The X-ray diffraction patterns showed the spinel ferrite type for CoFe2O4/Ser/Cu and amorphous SiO2 for MCM-41/Ser/Cu. The distinctive diffraction peaks in the diffraction curves of CoFe2O4/Ser/Cu, and MCM-41/Ser/Cu were identical to those of CoFe2O4, and MCM-41, confirming the preservation of these phases of supports throughout the functionalization processes and formation of -Ser/Cu moiety on the crystalline CoFe2O4 structure and non-crystalline silica structure. FE-SEM images showed the particles in CoFe2O4/Ser/Cu had an average diameter of 20–50 nm and in MCM-41/Ser/Cu had an average diameter of 50–250 nm. The images showed the uniformity and well-ordering of the particles. The slight aggregation in CoFe2O4/Ser/Cu particles implied that their clustering may be the result of modest attraction forces between them. MCM-41/Ser/Cu sample exhibited a type IV isotherm with an H1-type hysteresis loop and diagrams of the CoFe2O4/Ser/Cu showed a type IV isotherm (type H2 hysteresis loop). The MCM-41/Ser/Cu and CoFe2O4/Ser/Cu showed a mesoporous structure and capillary condensation occurred in the nearly cylindrical and ink bottle channels with non-uniform size or shape. The CoFe2O4/Ser/Cu showed surface area by BET and t-plot of 71.17 m2/g and 64.92 m2/g respectively, mean pore size of 14.06 nm, and pore volume of 0.250 cm3/g. The MCM-41/Ser/Cu showed surface area by BET and t-plot of 639.2 m2/g and 484.6 m2/g respectively, with a mean pore size of 5.44 nm, and pore volume of 0.869 cm3/g. The BJH pore size distribution was between 1 and 10 nm for the MCM-41/Ser/Cu and 1–20 nm for the CoFe2O4/Ser/Cu. Two catalysts were used for the synthesis of tetrazole. The CoFe2O4/Ser/Cu shows better activity in the synthesis of 5–substituted 1H-tetrazoles than the MCM-41/Ser/Cu sample despite its lowest surface area (71.17 m2/g). There is no reduction in the conversion of nitrile to tetrazole after the 6 cycles for CoFe2O4/Ser/Cu and after the 4 cycles for MCM-41/Ser/Cu.

Comparative predictive analysis using ANN and RCA for experimental investigation on branched and conventional micro heat pipe

The demand for compact, high-performance electronic devices rises, making thermal management in limited space crucial. This study presents a novel branched micro heat pipe (MHP) to solve this pressing problem. This novel method improves thermal performance for small-scale electronic cooling applications, surpassing conventional cooling methods. Innovative design has branched condenser of 12.7 mm evaporator, 24.6 mm adiabatic section and 12.7 mm condenser, each, compared to conventional MHP of identical size. Investigation encompasses a study of various parameters including working fluids, wettability characteristics, fill ratio, heat input, and cross-sectional geometries. The significant improvement in thermal performance by applying a hydrophobic surface treatment to the condenser section, increasing capillary force and condensate transport. Ammonia and de-ionized water excel thermal performance at lower and higher applied heat input (Qh), respectively. At higher Qh (>2 W), ammonia and toluene in the conventional MHP experience faster drying compared to the branched MHP, especially for lower fill ratio (0.6 FR). The branched MHP outperforms the conventional MHP, showing improved fluid circulation and performance, for fill ratios ranging from 0.65 to 0.4 and effectively transporting maximum heat flux in range of 10–14.4 W/cm2 with square mono-grooved MHP exhibits inferior performance compared to the trapezoidal and triangular mono-grooved. To provide a framework for future studies, we establish an artificial neural network (ANN) and statistical prediction model of thermal performance using the non-dimensional Kutateladze number (Ku), showcasing a robust correlation with experimental results and demonstrating only a minor deviation of ± 3 %.

Organosilica with tunable pore structure and antibacterial activity for intelligent humidity control

The spontaneous sorption and release of moisture by sorbents is proposed to be an energy-saving strategy for air humidity control. However, rational design of sorbents with humidity control ability and wide applicability still faces challenges. This study demonstrates quaternary ammonium-functionalized organosilica capable of controlling humidity intelligently and tuning humidity range as required. The prepared organosilica exhibited step-shaped water sorption isotherm due to its highly ordered pore structure, which was capable of precisely maintaining humidity within a narrow range. Importantly, the step position could be broadly tuned by easily changing the pore size during synthesis. Series organosilica with different pore sizes could realize humidity maintenance in 20%-40%, 40%-60% and 55%-80%, respectively, making it suitable for diverse humidity control applications. Grand Canonical Monte Carlo simulations elucidated the underlying mechanism of different water sorption behaviors in different pore structures. Quaternary ammonium groups act as the initial nucleation sites for water vapor, followed by distinct water condensation mechanisms in micropores (pore filling) and mesopores (capillary condensation), respectively. Moreover, organosilica exhibits efficient antibacterial activity and self-cleaning capability due to the function of quaternary ammonium groups. The organosilica with tunable pore structure and antibacterial activity provides a new model for intelligent and low-energy humidity control.

Small-Angle Scattering Indicates Equilibrium Instead of Metastable Capillary Condensation in SBA-15 Mesoporous Silica.

Questions about the origin of the adsorption/desorption hysteresis in mesoporous materials are as old as sorption experiments themselves. The historical conception that underlines most existing methods to extract pore size distributions from sorption data assumes that adsorption is a metastable process and that desorption takes place at thermodynamic equilibrium. In this work, we measure nitrogen and argon sorption on a series of 14 SBA-15 ordered mesoporous silicas and use small-angle X-ray scattering to independently determine their pore sizes. We find that capillary condensation systematically occurs close to thermodynamic equilibrium according to a Derjaguin-Broekhoff-de Boer calculation. Our analysis suggests that many earlier works have significantly underestimated the actual pore size in SBA-15 materials. It also highlights the critical role of the reference isotherm used to calibrate the fluid-solid interaction in the models.

The effect of traditional processing craft on the hygroscopicity of palm leaf manuscripts

Palm leaf manuscripts, which are crucial carriers of historical, religious, scientific, and artistic information in East and Southeast Asia, specifically encapsulate significant aspects of Buddhist culture and thus require comprehensive research and preservation efforts. The base material of palm leaf manuscripts is processed palm leaves, which are hygroscopic and profoundly affected by environmental humidity. Currently, there is a research gap regarding the impact of traditional processing crafts and natural aging on the hygroscopicity of palm leaf manuscripts. Utilizing dynamic water vapor sorption (DVS), the hygroscopic properties of palm leaves from various years were assessed before and after traditional processing in Yunnan Province, China. The results show that traditional processing slightly increases the equilibrium moisture content (EMC) in environments with 0 to 60% relative humidity (RH), but significantly lowers EMC in high humidity environments, with reductions up to 19.01%. Additionally, hysteresis doubled post-processing, indicating enhanced stability under fluctuating humidity conditions. Sorption models suggest that traditional processing increases the number of adsorption sites while reducing physical adsorption or capillary condensation. FT-IR (Fourier-transform infrared spectroscopy) analysis indicates that the relative contents of cellulose and hemicellulose were reduced by 39.90% and 3.97%, respectively. Degradation occurring in both the crystalline and amorphous regions of cellulose. After natural aging, the hygroscopicity of processed palm leaves improved across the entire humidity range of 0 to 95%, and there was a slight increase in hysteresis. This is due to the increase in both adsorption sites and physical adsorption capabilities. FT-IR results also indicate that the relative contents of cellulose and hemicellulose were decreased by 57.52% and 19.83% after nature aging, respectively. These findings confirm that traditional processing improves the writability and humidity resilience of the leaves, while natural aging enhances their overall hygroscopic properties. This research contributes to our understanding of how humidity damages palm leaf manuscripts. aids in determining optimal RH ranges for storage, and assesses the effectiveness of consolidation treatments in their long–term preservation.

Isoreticular Curves: A Theory of Capillary Condensation To Model Water Sorption within Microporous Sorbents.

Metal-organic frameworks have gained traction as leading materials for water sorption applications due to precise chemical tunability of their well-ordered pores. These applications include atmospheric water capture, heat pumps, desiccation, desalination, humidity control, and thermal batteries. However, the relationships between the framework pore structure and the measurable water sorption properties, namely critical relative humidity for condensation, maximal capacity, and pore size or temperature for the onset of hysteresis, have not been clearly delineated. Herein, we precisely formulate these relationships by application of the theory of capillary condensation and macroscopic thermodynamic models to a large data set of MOF water isotherms. These relationships include a concept termed isoreticular curves that relates the critical pressure for pore condensation (α), gravimetric capacity (Qmax), and hydrophilicity (the Gibbs free energy for binding water, ΔG) as Qmax = a1(ΔG/ln α)2 + a2(ΔG/ln α), with constants a1 and a2 dependent upon the density and volume occupied by the linker and secondary building unit, and framework topology. Through this analysis, we propose guidelines for the maximization of sorption capacity at a given relative humidity with minimal hysteresis and discuss the theoretical limits for capacity at low relative humidity. This model provides an explanation for the lack of high-capacity frameworks at low relative humidity, as increasing pore size also causes an increase in relative humidity. We propose a loose upper bound of Qmax = -0.25(1/ln α)2 - 1.75(1/ln α) for the limit of maximal capacity at a given relative humidity in the dry regime. These guidelines are consequential for the design of new materials for water sorption applications.

Dynamic Change Characteristics and Main Controlling Factors of Pore Gas and Water in Tight Reservoir of Yan’an Gas Field in Ordos Basin

Tight sandstone gas has become an important field of natural gas development in China. The tight sandstone gas resources of Yan’an gas field in Ordos Basin have made great progress. However, due to the complex gas–water relationship, its exploration and development have been seriously restricted. The occurrence state of water molecules in tight reservoirs, the dynamic change characteristics of gas–water two-phase seepage and its main controlling factors are still unclear. In this paper, the water-occurrence state, gas–water two-phase fluid distribution and dynamic change characteristics of different types of tight reservoir rock samples in Yan’an gas field were studied by means of water vapor isothermal adsorption experiment and nuclear magnetic resonance methane flooding experiment, and the main controlling factors were discussed. The results show that water molecules in different types of tight reservoirs mainly occur in clay minerals and their main participation is in the formation of fractured and parallel plate pores. The adsorption characteristics of water molecules conform to the Dent model; that is, the adsorption is divided into single-layer adsorption, multi-layer adsorption and capillary condensation. In mudstone, limestone and fine sandstone, water mainly occurs in small-sized pores with a diameter of 0.001 μm–0.1 μm. The dynamic change characteristics of gas and water are not obvious and no longer change under 7 MPa displacement pressure, and the gas saturation is low. The gas–water dynamic change characteristics of conglomerate and medium-coarse sandstone are obvious and no longer change under 9 MPa displacement pressure. The gas saturation is high, and the water molecules mainly exist in large-sized pores with a diameter of 0.1 μm–10 μm. The development of organic matter in tight reservoir mudstone is not conducive to the occurrence of water molecules. Clay minerals are the main reason for the high water saturation of different types of tight reservoir rocks. Tight rock reservoirs with large pore size and low clay mineral content are more conducive to natural gas migration and occurrence, which is conducive to tight sandstone gas accumulation.

In Ukrainian

The contact wetting is one of the effective methods of studying the adsorption capacity of sorbents. The purpose of the work was to compare the experimentally obtained data on the adsorption capacity of shungite, obtained by the sessile drop method, and the results of modeling the behavior of liquid droplets on heterogeneous surfaces using the Boltzmann lattice method, and to show the suitability of the simplified version of the LBM method that we applied within the framework of a two-dimensional model for modeling complex cases of contact interaction between liquids and sorbent, when it cannot be carried out by the method of contact wetting. The adsorption properties of shungite with regard to the extraction of various impurities from water-alcohol solutions and the capability of the sorbent to recover were investigated by the method of contact wetting and analyzed by involving the data obtained by the methods of nitrogen adsorption, thermogravimetry and IR spectroscopy. It is shown that the adsorption properties of shungite are due to the presence on its surface of hydroxyl functional groups attached to carbon atoms in phenol or enol form, which give the surface hydrophilic characteristics. These groups play a key role in the adsorption of components from the liquid (aqueous) phase due to the formation of a hydrogen bond during the sorption of components from the liquid phase, and are restored after heating in the temperature range of 80–180 °C with the formation of carbon-containing gases and water. It has been found that silanol groups present in shungite do not participate in sorption. Compared to the original shungite sample, the sample after five cycles of adsorption is characterized by a noticeable effect of mass loss (1.8 %) in the temperature range of 80–180 °С. At the same time, the loss of mass is not significant at temperatures below 100 °С. This suggests that the sorbed substances are in the pores and not on the surface of shungite, and they begin to be removed only after heating above 100 °C. The LBM method was used to study fast-moving processes at the meso-level. A comparative analysis of the experimental data obtained by the method of contact wetting with the results of simulation by the Boltzmann lattice method within the framework of the two-dimensional model was carried out. 2D modeling by the LBM method turned out to be an effective means of studying capillary condensation in mesopores, anticipatory wetting of the solid phase, liquid penetration into a porous medium with different topologies, and the formation of anisotropic droplets and anisotropic bridges. The role of mesopores in the sorption process was analyzed by modeling the behavior of liquid droplets on heterogeneous surfaces and using data on the course of adsorption and capillary processes on the surface of a solid phase with different levels of porosity, roughness, and functional composition.

Statistical modeling of equilibrium phase transition in confined fluids

The phase transition of confined fluids in mesoporous materials deviates from that of bulk fluids due to the interactions with the surrounding heterogeneous structure. For example, adsorbed fluids in metal-organic-frameworks (MOFs) have atypical phase characteristics such as capillary condensation and higher-order phase transitions due to a strong heterogeneous field. Considering a many-body problem in the presence of a nonuniform external field, we model the host-guest and guest-guest interactions in MOFs. To solve the three-dimensional Ising model, we use the mean-field theory to approximate the guest-guest interactions and Mayer's f-functions to describe the host-guest interactions in a unit cell. Later, using Hill's theory of nanothermodynamics, we define differential thermodynamic functions to understand the distribution of intensive properties and integral thermodynamic functions to explain the phase transition in confined fluids. The investigation reveals a distinct behavior where fluids confined in larger pores undergo a discontinuous (first-order) phase transition, whereas those confined in smaller pores experience a continuous (higher-order) phase transition. Furthermore, it is observed that the free-energy barrier for low-density adsorbed fluid (LDAF) to high-density adsorbed fluid (HDAF) phase transitions is lower in confined fluids than in bulk fluids resulting in a lower condensation pressure relative to the bulk saturation pressure. Finally, the integral thermodynamic functions are succinctly presented in the form of a phase diagram, marking an initial step toward a more practical approach for understanding the phase behavior of confined fluids. Published by the American Physical Society 2024

KOH Activated Carbon Coated 3D Wood Solar Evaporator with Highest Water Transport Height and Evaporation Rate for Clean Water Production.

The water evaporation rate of 3D solar evaporator heavily relies on the water transport height of the evaporator. In this work, a 3D solar evaporator featuring a soil capillary-like structure is designed by surface coating native balsa wood using potassium hydroxide activated carbon (KAC). This KAC-coated wood evaporator can transport water up to 32cm, surpassing that of native wood by ≈8 times. Moreover, under 1kWm-2 solar radiation without wind, the KAC-coated wood evaporator exhibits a remarkable water evaporation rate of 25.3kgm-2h-1, ranking among the highest compared with other reported evaporators. The exceptional water transport capabilities of the KAC-coated wood should be attributed to the black and hydrophilic KAC film, which creates a porous network resembling a soil capillary structure to facilitate efficient water transport. In the porous network of coated KAC film, the small internal pores play a pivotal role in achieving rapid capillary condensation, while the larger interstitial channels store condensed water, further promoting water transport up more and micropore capillary condensation. Moreover, this innovative design demonstrates efficacy in retarding phenol from wastewater through absorption onto the coated KAC film, thus presenting a new avenue for high-efficiency clean water production.

ОПРЕДЕЛЕНИЕ ИНТЕГРАЛЬНОЙ И ДИФФЕРЕНЦИАЛЬНОЙ ПОРИСТОСТИ ЖАРОСТОЙКИХ БЕТОНОВ УСОВЕРШЕНСТВОВАННЫМ МЕТОДОМ КАПИЛЛЯРНОЙ КОНДЕНСАЦИИ

The article discusses the method developed by the authors for assessing the distribution of pores by their sizes, which consists in obtaining a desorption isotherm of a material that is previously completely saturated with liquid sorbate, which fills all the pores of the material. In this case, complete saturation is achieved not in the process of capillary condensation, but by saturation of the material during vacuuming.

Polyaniline/Graphene oxide composite as an Ultra-Sensitive humidity sensor

This paper investigated the humidity-sensing response of polyaniline/Graphene oxide (PGO) composites. Graphene oxide (GO) was synthesised using the improvised hummers method, and polyaniline (PANI) was synthesised using the chemical in-situ polymerisation process. By adding different weights per cent (wt%) of Graphene oxide (GO) to the polymer matrix, PGO composites were prepared. Structural and morphological properties of GO were confirmed by XRD, RAMAN, FTIR, SEM, EDX, and HR-TEM (elementary mapping) characterisations. The XRD, FTIR SEM and EDX proficiencies were employed to characterise the PGO composites. To experience the humidity response performance, the film of PANI, GO, and PGO samples was groomed by wedging the sample on an IDT substrate using a drop casting technique. Among the samples, the PGO-3 composite (polyaniline/Graphene oxide 15 wt%) depicted a maximum sensing response (SH) of 93.4 % with a dynamic timing behaviour of 4 s and 7 s. The Nobel characters, such as low accurate Sensing response, fewer detection limits (LOD), negligible hysteresis and perfect stability, were observed in the PGO-3 composite. The physical properties such as porosity, water content, and degree of swelling have been outstandingly enhanced in the PGO-3 composite compared to PANI and GO. The mechanism for sensing the PGO-3 composites was deliberately explained based on establishing superficial physisorption, chemisorption layers, and later capillary condensation.

Sorption Hysteresis: A Statistical Thermodynamic Fluctuation Theory.

Hysteresis is observed commonly in sorption isotherms of porous materials. Still, there has so far been no unified approach that can both model hysteresis and assess its underlying energetics. Standard approaches, such as capillary condensation and isotherms based on interfacial equations of state, have not proved to be up to the task. Here, we show that a statistical thermodynamic approach can achieve the following needs simultaneously: (i) showing why adsorption and desorption transitions may be sharp yet continuous; (ii) providing a simple (analytic) isotherm equation for hysteresis branches; (iii) clarifying the energetics underlying sorption hysteresis; and (iv) providing macroscopic and nanoscopic perspectives to understanding hysteresis. This approach identifies the two pairs of parameters (determinable by fitting experimental data) that are required to describe the hysteresis: the free energy per molecule within the pore clusters and the cluster size in the pores. The present paper focuses on providing mechanistic insights to IUPAC hysteresis types H1, H2(a), and H2(b) and can also be applied to the isotherm types IV and V.

Cross-Polarization Solid-State NMR Quantification of Species within Pores of Metal-Organic Frameworks: A Case Study of α-Mg3(HCOO)6.

The quantitative measurement of adsorbed guest species within metal-organic framework (MOF) pores is of fundamental importance for evaluating the adsorption performance of MOFs. However, routine analytic techniques such as thermogravimetric analysis cannot distinguish the contribution from species adsorbed within pores, species adsorbed on the surface, and gas phase or liquid phase encapsulated in the inter-crystalline space. Herein, we developed a new quantification method based on the cross-polarization (CP) solid-state nuclear magnetic resonance (ssNMR) technique, in which only the species within MOF pores are selectively probed due to the dramatically reduced mobility. Using the commercialized MOF α-Mg3(HCOO)6 as an example, a good linear correlation between Areaguest/Areaframework (i. e., the integrated area of guest and framework 13C NMR signals) and guest loading can be observed for several representative molecules such as benzene, tetrahydrofuran (THF), and 1,4-dioxane, clearly revealing the feasibility of CP quantification approach. The effects of guest molecule and corresponding residual mobility on the CP quantification are further discussed by varying the geometry and size of guest molecules. This methodology thus provides an effective and irreplaceable route to evaluate the adsorption performance of porous materials in-depth, especially for liquid-phase adsorption and gas-phase adsorption in which the capillary condensation is not negligible.

Capillary Condensation Mediated Fluidic Straining for Enhanced Bacterial Inactivation

AbstractBiomaterials 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.