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It is widely known that the impact of atmospheric humidity on tribological phenomena is significant, particularly in the context of dry sliding. Previous reviews have comprehensively addressed various cases within this domain and this article aims to complement these reviews with recent findings. The review covers a wide spectrum of humidity levels, ranging from trace amounts of water in the order of a few vol ppb to the relative humidity levels experienced in daily life. It delineates the forms of adsorbed water on solid surfaces within each humidity range and explores the potential physical lubrication mechanism of the adsorbed water and its effects on tribological phenomena. In the past, explanations for this influence have tended to be qualitative, primarily viewed from the perspective of chemical reactions. This discussion seeks to broaden the understanding by considering the influences from a physical lubrication perspective. Concluding the review, recent research findings are presented, shedding light on instances where trace amounts of water present in gases such as hydrogen exert an influence on tribological phenomena.

The coal chemical industry, as the main source of carbon emissions in China, will face great challenges under the constraints of the dual carbon goals. Coal derived gas deep desulfurization is an important component for highly efficient and clean utilization of coal, which is of great significance for carbon reduction. Zinc oxide is a commonly used adsorbent for desulfurization, but due to kinetic limitations, its room temperature desulfurization reactivity is very low, and this cannot meet the requirements of industrial application. Pore diffusion is a prerequisite for the reaction between ZnO and H2S, and is crucial for desulfurization performance. However, the influence of pore size, especially macropores, on the desulfurization performance and its mechanism have been rarely reported. For this reason, two ZnO/SiO2 adsorbents with mesopores and macropores in this study were prepared using a sol-gel method and a colloidal crystal template method, respectively, and the influence of macropores on their room temperature desulfurization performance was explored. It is found that although the introduction of macropores increases the specific surface area of the adsorbent, strengthens its surface alkalinity, improves the dispersion of ZnO, and increases the concentration of oxygen vacancies in the adsorbent, its introduction leads to a remarkable decrease in the desulfurization performance of adsorbent. The breakthrough sulfur capacity of mesoporous adsorbent is 151.9 mg/g, 2.3 times than that of macroporous adsorbent. This is because the macroporous structure is unstable and prone to collapse during the desulfurization process, which hinders the accessibility of reaction sites of ZnO; Secondly, the water vapor in the atmosphere is not conducive to the formation of a water film on the surface of macropores, thereby inhibiting the occurrence of desulfurization reactions. More importantly, the combustion of the template releases a large amount of heat during the preparation of macropores, which leads to a deep crosslinking of the SiO2 network and a decrease in the mesoporous pore size of adsorbent. The smaller mesoporous pore size results in an excessive amount of water physically adsorbed on its surface, inhibiting the reaction between ZnO and H2S.

The physical meaning of the neutral stress and effective stress for soils is still unclear, which leads to the neutral stress for unsaturated soils being totally ignored and increasingly complicated expressions for effective stress. To solve these problems, we establish an extended three-phase physical model for unsaturated soils, including capillary water, pore air, and generalized soil skeleton (GSS) and then derive a generalized Terzaghi's effective stress equation, stating that the effective stress is equal to total stress minus neutral stress. In our equation, the neutral stress consists of three components, i.e. the homogenized pore fluid pressure, the stress acting on the cross sections of soil particles, and the stress acting on the contacts between particles. The mechanical effects of the neutral stress can be appreciable, especially in unsaturated clays at a relatively low saturation. The effective stress is found to be the stress that is transmitted through GSS. The local stress, induced by physicochemical forces, cementation, and surface tension, is not transmitted through GSS, and thus, it should not be added into effective stress equation. The mechanical effects of the effective stress are controlled by the mechanical parameters of GSS expressed as a function of suction besides the effective stress itself. Integrating the mechanical effects of neutral stress and effective stress, a general framework is proposed for describing the mechanical behaviour of unsaturated soils. Under the framework, the proposed shear strength equation is in very good agreement with the experiment data reported in the literature. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A numerical model that simulates methane transport and adsorption in crushed shale was developed. This model uses the finite element method to solve the diffusion coefficient (D) and adsorption rate of methane in a spherical particle region, and it was calibrated by fitting experimental data on the adsorption process of methane in unsaturated crushed shale. The results show that the methane free concentration in shale reflected the strength of methane's diffusion ability. The D increased by 2.2–4.9 times for each 900 mol/m3 increment in the free concentration. The D was 1.43 × 10−11–1.23 × 10−9 m2/s as the boundary concentration ranged from 461 to 2766 mol/m3. Furthermore, the diffusion behavior can be divided into three stages during the adsorption–diffusion process. The increasing trend of the D was slow in the early and late stages of the adsorption–diffusion process, while the D obviously increased in the middle stage. The middle period accounted for 16.2–71.7% of the entire process. Moreover, the variation in the D along the radial axis that started at the center of the model and pointed to the model surface can be divided into two regions. The change in the D tended to be horizontal in a region close to the center, whereas in the other region, the D was positively correlated with the distance to the center. The horizontal area decreased as adsorption–diffusion proceeded, and the rate of shrinkage of this area can be described with an exponential equation. [ABSTRACT FROM AUTHOR]

The effect of adsorbed water layers in sliding phenomena has been widely recognized, but it has yet to be explained thoroughly after many years of research. Previous researches tend to explain the phenomena from chemical and qualitative viewpoints, thus physical viewpoint approaches with quantitative evidence are necessary to complement the previous research works. Studies were done to estimate the thickness of adsorbed water layers in recent years to obtain quantitative evidence of the effect of adsorbed water layers. It was found that the thickness of the adsorbed water layer derived from atmospheric humidity could provide physical influences on sliding phenomena. The hypothesis in this study based on the Stribeck curve is; the friction coefficient may decrease significantly with the increase of sliding speed at high relative humidity (RH) compared to low RH. To verify the hypothesis, a pair of JIS SUS304 austenitic stainless steel balls were scratched against each other horizontally with a vertical overlapping distance of 80 µm at sliding speeds of 20, 200, and 2000 µm·s−1 in RH of 5, 55, and 95%. The experimental results supported the hypothesis as the friction coefficient for medium to high RH decreased significantly with increasing sliding speed while the friction coefficient decreases slightly at low RH. The friction coefficient decreases significantly at high sliding speed and RH. The possible physical effects of the adsorbed water layers were suggested.

The soil freezing characteristic curve (SFCC) represents the constitutive relationship between sub‐zero temperature and unfrozen water content in soil. It governs the hydrologic and mechanical behaviors associated with freezing soil. Numerous studies have investigated the mechanisms of soil water freezing and attempted to predict SFCC using soil water characteristic curve (SWCC) and Clapeyron equation. However, limited attention has been given to the physical disparities between adsorbed and capillary water during freezing, including variations in pressures and water‐ice interfaces. In this study, we present a novel theoretical model for predicting SFCC. The model determines the freezing point by calculating the chemical potential of soil water and ice with their respective pressures, thus capturing the distinctions in freezing behaviors between adsorbed and capillary water. All model parameters possess clear physical interpretations, and the model solely relies on the SWCC as input. The validity of the proposed model was confirmed through experimental measurements involving the water phase diagram, SWCCs, and the corresponding SFCCs of sandy, silty, and clayey soils. The model exhibits strong capabilities in predicting SFCC regardless of the soil type and outperforms the conventional method in predicting the SFCC of soil with high adsorbed water content. Model analyses were performed to investigate the effects of individual pore size, soil type, and initial water content on the freezing process, revealing the distinct contributions of adsorption and capillarity in soil water freezing. This study elucidates the mechanisms underlying soil water freezing, offering a theoretical framework for the analysis and prediction of frozen soil behaviors. Plain Language Summary: The freezing point of soil water is lower than that of free water, and the relationship between sub‐zero temperature and unfrozen water content is soil freezing characteristic curve (SFCC). The unfrozen water content is important for the physical processes in soil. Soil water content comprises adsorbed water and capillary water. They are retained in soil by different physical mechanisms, that is, adsorption and capillarity. As a result, they exhibit distinct freezing behaviors. However, the freezing of adsorbed water has been overlooked in many studies. This work established a theoretical SFCC model based on the chemical potential equilibrium between pore water and ice. The model can describe the freezing of adsorbed and capillary water and only requires the soil water characteristic curve (SWCC) as input. Experimental water phase diagram, SFCCs, and SWCCs validated this model. The model can predict the SFCC of various soils and is superior to the conventional method in predicting the SFCC of soils with high adsorbed water content. The clear physical mechanism in the model enables the analysis of the effects of pore sizes, soil types, and initial water content on unfrozen water content. This work provides a useful tool to predict frozen soil behaviors. Key Points: A theoretical soil freezing characteristic curve (SFCC) model considering the physical disparities between adsorbed and capillary water is establishedThe model exhibits advantages in predicting the SFCC of soils with high adsorbed water contentThe model can illustrate the effects of soil types and initial water contents on SFCC [ABSTRACT FROM AUTHOR]

In this work, the effects of adsorbed water on the structural evolution in the PVDF layer of composite hydrophobic MFFC-3 and hydrophilic MFFC-3G membranes were studied using ATR IR spectroscopy. It has been found that adsorbed water molecules initiate the conformational rearrangement of PVDF polymer molecules in the hydrophilic membrane layer, while the conformation of PVDF polymer molecules in the hydrophobic membrane layer does not change. The deconvolution of the absorption bands of the stretching vibrations of OH groups was carried out using four Gaussians. Based on the frequencies of the Gaussian peaks, the energy was calculated and the hydrogen bonds of adsorbed water were classified. It is shown that the structure of adsorbed water with hydrogen bond energies EOH = 42.8, 35.7, 17.9, and 14 kJ/mol are "clusters" with three or four hydrogen bonds. Energy values EOH = 17.9, 10.6, 16.8, and 14 kJ/mol correspond to OH bonds of dimeric and monomeric water molecules. It is concluded that the structure of adsorbed water in the PVDF layer can be characterized by a mixed model of hydrogen bonds, consisting of monomeric, dimeric molecules, and associated clusters with hydrogen bond energies from 10.6 to 42.8 kJ/mol. A comparative analysis of the ATR IR spectra of water-saturated samples indicates that the adsorbed water molecules in the PVDF "polymer–water" interfacial space of the hydrophobic membrane do not form a layer of bound water, while, in the hydrophilic membrane, water enters the structure of molecules, forming a layer of bound water. [ABSTRACT FROM AUTHOR]

A soil water unit weight of 9.8 kN/m3 has been universally considered to quantify soil volumetric phase properties such as void ratio and degree of saturation, but has been found to greatly vary depending on soil type and the volume scale with which it is defined. Recent experimental and theoretical evidence has indicated that the unit weight of soil water can be significantly greater than 9.8 kN/m3 for clayey soils when gravimetric water content is less than 30%. A soil water unit weight as high as 18.8 kN/m3 is evident for some expansive soils at low water content. The significance of abnormally high water unit weight in quantifying soil phase volumes, saturation, and void ratio was experimentally assessed for various clayey soils and theoretically interpreted as a function of water content and soil type. For clayey soils with low liquid limit, average soil water unit weight can be as high as 12.5 kN/m3 for gravimetric water content less than 10%. This leads to an overestimation of liquid-phase saturation and void ratio by as much as 8% if a soil water unit weight of 9.8 kN/m3 is used. For clayey soil with a high liquid limit, the average soil water unit weight can be as high as 18.8 kN/m3 for water content less than 18%, leading to overestimation of liquid-phase saturation by as much as 36% and void ratio by as much as 20% if 9.8 kN/m3 is used. Charts were developed to estimate average soil water unit weight as a function of soil specific surface area and water content, and as a function of liquid limit and water content. The commonly used value of 9.8 kN/m3 for water unit weight can lead to significant errors in estimating phase volumes, void ratio, and saturation for clayey soils. [ABSTRACT FROM AUTHOR]

As a common geological material, soil is a key aspect of construction engineering. Soil has typical multi-scale characteristics, but current multi-scale methods analyze these characteristics only in regard to geometric space. More exploration of the coupling influence mechanism of the basic properties of particles on the microstructure and macroscopic properties of soil is needed. This study analyzed the influence of geometric scale and mineral composition on the surface energy of particles at the microscopic level for development of the energy multi-scale method. Experiments were performed to determine the influence of mineral composition and particle size on the plasticity index (Ip) of the soil, and experimental results are discussed and interpreted quantitatively using the energy multi-scale method. The conclusions derived from this work are as follows: 1) the mineral composition and particle size of the soil can cause interface and surface effects; 2) the comprehensive ratio of micro-force to weight (CRFW) of the particles can be determined using the energy multi-scale method and quantitatively reflects the influence of particle size and mineral composition on the microscopic properties of the soil; and 3) the energy multi-scale method explains the mechanism of the plasticity index of soil and has allowed identification of a new division of soil plasticity. When the CRFW was used as the control index, the plasticity index of the three materials was practically the same, even if the mineral composition and particle sizes of the three materials were different.

The study of the creep properties of soils is of great importance for the management of future settlements and the safe use of buildings. However, starting from the micro level is an effective way to explore the creep mechanism of soft soil. In this paper, the influence of the mineral composition and the mineral content on the structure and creep properties of soft soil was analyzed at the microscopic level and the energy scale method was proposed. Then, the energy scale method was used to analyze and discuss the results of the direct shear creep test. The discussion showed that 1) the average viscosity coefficient of kaolin was greater than that of bentonite, which decreased with an increase of kaolin and bentonite; 2) the thickness of adsorbed water or the double electric layer (DEL) on the particle surface was positively correlated with the soft soil creep; and 3) λ was positively correlated with the adsorbed water content and negatively correlated with the average viscosity coefficient of the soft soil. λ characterized the adsorption capacity of the particles at the micro level; hence, the energy scale method can explain the mechanism of the soft soil creep at the microscopic level and also quantitatively describe the influencing law of the basic characteristics of the particles on the properties of the soft soil creep.

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In recent years, accurate determination of the effective stress factor has been found to be instrumental for classifying the types of pore water and defining the form of their contribution to the unsaturated soil strength. In this study, a series of laboratory experiments based on volumetric flask, indoor evaporation and low-field nuclear magnetic resonance (NMR) methods were conducted on Wuhan clay to determine the relationship between adsorbed water content and matrix suction, and hence the adsorbed water retention curve (AWRC). The capillary water retention curve (CWRC) is the curve derived by subtracting the AWRC from the soil water characteristic curve (SWCC). This CWRC is then utilized to obtain correlation between the degree of saturation of capillary pores (Scap) and the matrix suction. The effective stress factor was replaced with Scap for determining the shear strength of Wuhan clay with three different dry densities. It was observed that the predicted values of shear strength obtained by NMR-based methods are more accurate than two other methods available in the literature. Furthermore, the accuracy of the method is not impacted by changes in dry density or confining pressure. [ABSTRACT FROM AUTHOR]

Frost heave and thaw settlement are primarily caused by water migration. Variations in liquid water and its components during freezing and thawing are crucial variables for investigating water migration. Here, a novel soil layer‐scanning method based on magnetic resonance imaging cryogenic soil‐moisture analysis (MRI‐CSMA) was applied to measure dynamic changes of liquid water and its components in nine layers (each 11.1‐mm thick) of four loess samples with different initial water contents (9.2%, 15.7%, 20.0%, and 30.0%) in freezing–thawing experiments under a closed system. The ice–water phase transition and water migration were key factors that controlled the liquid water and its components. During freezing, the liquid water content of each layer (except layer 7) decreased. In the frozen zone (layers 1–6), the liquid water content decreased with decreasing temperature owing to the water–ice phase transition. The lower the temperature, the higher the fraction of water that transitioned to ice. In the unfrozen zone (layers 8–9), parts of the liquid water migrated upward owing to the suction generated at the freezing front. The farther away the freezing front, the smaller the suction and quantity of water migration. During thawing, the liquid water content of each layer increased owing to the ice–water phase transition in the frozen zone and infiltrated down to the unfrozen zone. The contents of the free and adsorbed water exhibited similar change trends to the liquid water content during freezing. However, the change degree of free water was much larger than that of adsorbed water because the phase transition and migration of free water is easier than that of absorbed water. Notably, the liquid water content near the freezing front (layer 7) increased in the early stage of freezing, owing to the combined effect of soil compression and the water–ice phase transition. These results provide a reference for research on water migration in the soil during freezing–thawing and validate the advantage of MRI‐CSMA when characterising water migration in large soil samples. Highlights: A novel device (MRI Cryogenic Soil‐Moisture Analyzer) was used.Variations in unfrozen water and its components during freezing were studied.Soil consolidation and pore pressure affect the liquid water change during freezing. [ABSTRACT FROM AUTHOR]

In the temperature programmed desorption-mass spectrometry (TPD-MS) experiments, the time lag and broadening of the gas evolved from the sample until it is detected by the MS detector can be a problem. The deconvolution method was successfully applied to TPD-MS. The pulse injection of N2, 1-butene, CO2, and H2O gasses in the TPD-MS system showed the same MS intensity-time response. This result suggests the MS signal can be used as an impulse response function of deconvolution analysis. The present TPD-MS method was applied to evaluate the dehydration from zeolites during heating. The shape of differential thermogravimetry (DTG) curves was in good agreement with deconvolved TPD-MS curves. The signal-to-noise ratio of TPD-MS is higher than that of DTG. The present method can be applicable for TG-MS or Fast scanning calorimetry (FSC)-MS in the upcoming study.

Summary: The long‐standing hypothesis that the isotopic composition of plant stem water reflects that of source water is being challenged by studies reporting bulk water from woody stems with an isotopic composition that cannot be attributed to any potential water source. The mechanism behind such source–stem water isotopic offsets is still poorly understood.Using a novel technique to extract selectively sap water from xylem conduits, we show that, in cut stems and potted plants, the isotopic composition of sap water reflects that of irrigation water, demonstrating unambiguously that no isotopic fractionation occurs during root water uptake or sap water extraction. By contrast, water in nonconductive xylem tissues is always depleted in deuterium compared with sap water, irrespective of wood anatomy.Previous studies have shown that isotopic heterogeneity also exists in soils at the pore scale in which water adsorbed onto soil particles is more depleted in deuterium than unbound water. Data collected at a riparian forest indicated that sap water matches best unbound soil water from depth below −70 cm, while bulk stem and soil water differ markedly.We conclude that source–stem isotopic offsets can be explained by micrometre‐scale heterogeneity in the isotope ratios of water within woody stems and soil micro‐pores. [ABSTRACT FROM AUTHOR]

Formulation of an effective stress equation for unsaturated soils where all relevant physical characteristics are included has challenged researchers for several decades. On one hand, the interfacial forces and the contractile skin have recently been understood to be of significant contribution to the effective stress, particularly at low degrees of saturation. On the other hand, the microstructural effects play a significant role, especially in fine-grained soils. In this study, an equation is proposed for the effective stress parameter (χ ) based on the recent advances in modeling the adsorbed water, and thereby determining the capillary water retention curves. In the proposed relationship, both the microstructural effect and interfacial forces are taken into account. Additionally, in formulating effective stress, these two aforementioned aspects have been considered and formulated for both drying and wetting conditions. To this end, the interfacial forces were determined based on the capillary water content. Next, the proposed model was further simplified to reduce the number of unknown parameters to one with the rest of the parameters readily available from the soil water retention curve. The simplified formulation agrees fairly well when compared with the experimental data on soils experiencing both drying and wetting paths. Furthermore, assessing the performance of the proposed model, compared with the available equations incorporating the contribution of the interfacial forces, indicates the superiority of the proposed model for the eight soil types examined in this study. [ABSTRACT FROM AUTHOR]

The hydration behaviour of unsaturated expansive clays, crucial for applications such as radioactive waste management, remains a challenging and incompletely understood phenomenon given the complexity of characterizing their pore network dynamics upon water absorption. The evolution of porewater populations, distinguished as immobile adsorbed water attached to the clay particles surface and capillary water, presumably governs the kinetics of water mobility in wetting or drying processes. Nuclear Magnetic Resonance (NMR) relaxometry experiments have reported the increase of water mobility during the wetting process of expansive clays but the evolution of water populations remained unidentified. This study presents relaxation time distributions and relaxation time maps found for a bentonite/sand mixture (with Na-montmorillonite) at various relative humidities, reproducing its hydration. Valuable insights into particular experimental procedure, data-treatment and interpretation for expansive clay are provided. Relaxation times in Na-montmorillonite highlighted a two-regime evolution as a function of water content, in accordance to models, featuring the properties of adsorbed water, which is considered fully dominant during the first regime (relative humidity lower than 90%). An empirical model reproducing the two-regime dependance of water content on relaxation times was proposed. Moreover, a new formulation enabled quantifying the adsorbed water fraction in expansive clay from relaxation time measurements. Finally, the porewater populations were quantified for Na-montmorillonite as a function of water content, demonstrating strong agreement with supercooling observations in freezing experiments. [Display omitted] • Water mobility in unsaturated Na-montmorillonite describe a transition point at relative humidity of 90%. • Water becomes mobile in unsaturated Na-bentonite for relative humidity above 90%. • NMR relaxation times quantifying the adsorbed water fraction in expansive clay. • An empirical model reproducing T 2 relaxation times as a function of water content • Prediction of adsorbed water fraction in function of water content for Na-montmorillonite [ABSTRACT FROM AUTHOR]

Flowback and produced water is causing water environment pollution and elevated disposal costs during the shale gas development. Due to high salinity and variously hazardous substances in the connate pore water (i.e., initial water storing in shale matrix pores), whether the connate pore water is produced in company with fracking water flowback has long been concerned. The key is to determine the mobility of connate pore water, which is closely associated with the occurrence of adsorbed and free water in shale pores. In this study, five fresh shale samples were obtained from the Longmaxi Formation shale gas reservoirs in the southern Sichuan basin of China to evaluate the mobility of connate pore water. Theoretical models of describing the non-equilibrium and equilibrium expulsion processes of connate pore water from shale matrix were proposed. On this of basis, the amounts and microscopic distributions of adsorbed and free water in the shales were determined by using centrifugation and nuclear magnetic resonance (NMR) tests under atmospheric pressure and 30 °C temperature condition. Results show that: (1) the amounts of adsorbed and free water in the shales varies from 5.9132 to 8.3442 mg/g (mean 7.3842 mg/g) and 2.1224–5.7931 mg/g (mean 3.9507 mg/g), respectively. The amount of free water (i.e., maximum mobile water amount) accounts for 23.69–41.37 wt% (mean 34.12 wt%) of total water, indicating that about one-third of the connate pore water in gas shales is potentially recoverable. (2) The connate pore water in the adsorbed and free states mainly distributes in the pores of 0.5–10 nm, of which the adsorbed water mainly distributes in the pores of 0.5–3 nm and the free water (i.e., mobile water) mainly stores in the pores of 3–10 nm. (3) The mobility index, that is the ratio of free water amount to mid-value pressure difference, was introduced to quantify the mobility of connate pore water by considering the equilibrium expulsion process of pore water. The mobility index of connate pore water in fresh shales is negatively related to the water-adsorbed ratio. This study contributes to identifying the source of flowback and produced water and is also significant to water environment. • Models of describing the non-equilibrium and equilibrium expulsion processes of connate pore water from shale were proposed. • Amounts and micro distributions of adsorbed and free water in shales were determined by using centrifugation and NMR tests. • Potential and distribution of mobile water in fresh shales were revealed. • Mobility index was introduced to quantify the mobility of connate pore water. [ABSTRACT FROM AUTHOR]

The NMR-based solvent relaxation technique, a non-invasive tool to characterize the surface of particles, which are dispersed in a liquid, was applied to characterize the nanoparticles’ aggregation structure. The liquid molecules in a dispersion undergo a rapid exchange between the bound states at the interface and highly mobile free states in a bulk liquid. The relaxation time of the liquid molecules bound on the particle surface is shorter than that of the free states liquid. By detecting how much liquid is bound on the particle surface, the wetted specific surface area (SNMR) can be determined. In this study, it was clarified that the water adsorbed at more than a 1.138 layer from the silica surface can be detected by the NMR and the maximum limitation ranged from 2.160 and 3.336 layers. The model aggregates with an artificial solid neck among the particles were mixed with the silica nanoparticle dispersion. Although the determined SNMR was underestimated compared to SBET from gas adsorption, even a low ratio (5 mass%) of the model aggregates in the dispersion can be detected.

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The influence of the modification of the TiO2 surface with F− ions on the physicochemical properties of the catalysts and efficiency in the photooxidation of gaseous molecules under atmospheric conditions and under UV irradiation was studied by IR spectroscopy. The fluorine-containing samples adsorb more water molecules than unmodified TiO2. The amount of adsorbed water increases with increasing content of surface fluoride ions. The fluorination of the TiO2 surface first leads to the substitution of the terminal OH groups by F− ions and to an increase in acidity of the bridging acidic OH groups remained on the surface. The modification also results in the structural rearrangement of the surface involving defective and surface Ti4+ sites. Fluorine modification increases the activity of TiO2 in the photocatalytic oxidation of ethanol, acetaldehyde, acetic acid, and acetone. At the same time, benzene and H2S are oxidized more rapidly on unmodified TiO2. The presence of fluorine on the TiO2 surface exerts almost no effect on the oxidation rate of chlorine-containing substrates C3H7Cl and C2H4Cl2. [ABSTRACT FROM AUTHOR]

Abstract Aim of this research was to evaluate the relationship between the biometrics of vessel-ray pits (RVP) and intervessel pits (IVP) with the water flow in different axes of Corymbia citriodora wood. C. citriodora wood specimens were used to correlate RVP and IVP dimensions with free water (FWFR), adsorbed (AWFR) and total (TWFR) flow. Correlations were made for three wood axes. Larger diameters of RVP facilitated FWFR, AWFR and TWFR in axial and tangential axis, however reduced permeability in radial direction of wood. Larger openings of IVPs reduced FWFR, AWFR and TWFR in axial axis of wood. Larger IVPs openings allowed higher FWFR and TWFR in wood radial and tangential directions, however, concomitantly reduced AWR. Effect of diameter of RVP and IVP on wood permeability should be evaluated for each axis. Thus, the opening of the C. citriodora wood pits can interfere in its permeability and consequently in its processing.

Results and analysis of internal reflection spectral absorbance experiments are reported for near-infrared (NIR) spectra obtained using an optical fiber sensor system. We present a preliminary study to diagnose the efficacy of our fiber optic system to observe and distinguish various phases of water, i.e., ice, liquid, and adsorbed. This study was motivated by the need for a technique capable of obtaining soil water content measurements in real time and in situ, at low humidity conditions for simulation studies of planetary bodies such as Mars. Spectral signatures were observed for the solid, liquid, and adsorbed phases of water. For all phases, peak absorbance at λ ≈1.45 and 1.94 μm was observed despite slight peak shifting due to dispersion effects. Dispersion effects commonly obscure spectra obtained with internal reflection spectroscopy for particular spectral regions. Here we report a spectral region with minimal distortions. Internal reflection spectra were compared directly to transmission spectra with only slight variations. Spectral matching was performed to determine sample penetration depths for unknown incidence angles. In general, relative absorbance and spectral shifting can distinguish spectra of the various phases of water. [ABSTRACT FROM AUTHOR]

To identify the subsidence induced by an offshore earthquake, chemical compositions, fossil assemblages, and radiocarbon ages of organic materials were analyzed for Holocene sediments in the Miyazaki Plain, southwest Japan. The lower sedimentary facies (SF1) composed of sand‐ and pumice‐rich sediments and the upper sedimentary facies (SF2) composed of silt‐rich sediments were identified by stratigraphical description. Sharp facies changes and sediment disturbances are observed in the boundary between SF1 and SF2. Diatoms of brackish and marine water origins, foraminifers, ostracods, and mollusks are common in SF2, while fossils are rare, and most of them are diatoms of freshwater origins in SF1. The stratigraphical and paleontological evidences suggest an environmental change from the lower terrestrial to the upper shallow marine. The change is laterally continuous and seems to be inconsistent with Holocene uplift trends in the Miyazaki Plain. Radiocarbon ages of organic matters and the occurrence of the Sakurajima–Bunmei tephra (1471–1476 ad) show that the environmental change could be attributed to local subsidence due to the 1662 Kanbun Hyuganada Sea earthquake shown in historical records. The chemical analysis shows clear contrast between SF1 and SF2 in terms of concentrations of cations and anions commonly rich in seawater (i.e. Na+, Mg2+, K+, Ca2+, Cl−, and SO42−) in adsorbed water extracted from the sediments, and total S concentrations in bulk sediments, supporting the environmental change from terrestrial to shallow marine. However, the bulk chemical composition, except total sulfur, remains rather unclear for use as marine‐derived chemical markers compared to the adsorbed water, because it is more affected by the composition of the source sediments. [ABSTRACT FROM AUTHOR]

The NMR-based solvent relaxation technique, a non-invasive tool to characterize the surface of particles, which are dispersed in a liquid, was applied to characterize the nanoparticles' aggregation structure. The liquid molecules in a dispersion undergo a rapid exchange between the bound states at the interface and highly mobile free states in a bulk liquid. The relaxation time of the liquid molecules bound on the particle surface is shorter than that of the free states liquid. By detecting how much liquid is bound on the particle surface, the wetted specific surface area (SNMR) can be determined. In this study, it was clarified that the water adsorbed at more than a 1.138 layer from the silica surface can be detected by the NMR and the maximum limitation ranged from 2.160 and 3.336 layers. The model aggregates with an artificial solid neck among the particles were mixed with the silica nanoparticle dispersion. Although the determined SNMR was underestimated compared to SBET from gas adsorption, even a low ratio (5 mass%) of the model aggregates in the dispersion can be detected. [ABSTRACT FROM AUTHOR]

The effect of a Cu2O substrate on the photoinduced alteration of the hydrophilicity of TiO2 and ZnO surfaces was studied. It was demonstrated that the formation of heterostructures Cu2O/TiO2 and Cu2O/ZnO strongly changed the direction of the photoinduced alteration of surface hydrophilicity: while both TiO2 and ZnO demonstrate surface transition to superhydrophilic state under UV irradiation and no significant alteration of the surface hydrophilicity under visible light irradiation, the formation of Cu2O/TiO2 and Cu2O/ZnO heterostructures resulted in photoinduced decay of the surface hydrophilicity caused by both UV and visible light irradiation. All observed photoinduced changes of the surface hydrophilicity were compared and analyzed in terms of photoinduced alteration of the surface free energy and its polar and dispersive components. Alteration of the photoinduced hydrophilic behavior of TiO2 and ZnO surfaces caused by formation of the corresponding heterostructures with Cu2O are explained within the mechanism of electron transfer and increasing of the electron concentration on the TiO2 and ZnO surfaces.

The effective permittivity of low-density polyethylene with the conductive carbon black (CB) was modelled by COMSOL. The impact of CB content on the electric properties of the composites with different geometry of the inclusions was investigated. The modelling outcomes evidenced that the simulation was in good agreement with the experiment results at low-filler concentration. The effect of moisture on the effective permittivity of the composites was also investigated. A thin layer of adsorbed water on the surface of the CB particles was found to significantly increase the conductivity, which is in agreement with experimental results.

The molecular mechanism of the adhesion between silica surface and epoxy resin under atmospheric conditions is investigated by periodic density‐functional‐theory (DFT) calculations. Slab models of the adhesion interface were built by integrating a fragment of epoxy resin and hydroxylated (0 0 1) surface of α‐cristobalite in the presence of adsorbed water molecules. Effects of adsorbed water on the adhesion interaction are evaluated on the basis of geometry‐optimized structures, adhesion energies, and forces. Calculated results demonstrate that adsorbed water molecules significantly reduce both the adhesion energies and forces of the silica surface–epoxy resin interface. The reduction of adhesion properties can be associated with structural deformation of water molecules confined in the tight space between the adhesive and adherend as well as structural flexibility of the hydrogen‐bonding network in the interfacial region during detachment of the epoxy resin from the hydrophilic silica surface. © 2018 Wiley Periodicals, Inc. The molecular mechanism of the adhesion between silica surface and epoxy resin under atmospheric conditions is investigated by using periodic density‐functional‐theory (DFT) calculations. Effects of adsorbed water on the adhesion interaction are evaluated on the basis of geometry‐optimized structures, adhesion energies, and forces. Calculated results demonstrate that adsorbed water molecules significantly reduce both the adhesion energies and forces of the silica surface–epoxy resin interface. [ABSTRACT FROM AUTHOR]

• The physical and mechanical properties of fused silica are studied after various depths of subsurface damage removal by reactive ion etching process. • Concentration of metal ions contamination in the subsurface of fused silica decreases with the etching depth. • Homogeneity of adsorbed water molecules on fused silica surface increases with the etching depth, especially at higher humidity conditions. • Nanohardness and reduced modulus of fused silica increases with the etching depth. The subsurface damage of polished fused silica can be removed by various post-treatments to improve the strength of fused silica in high energy laser systems, but the evolution of physical and mechanical properties of fused silica after the removal of subsurface damage remains unclear. In this study, the physical and mechanical properties of fused silica are studied after various depths of subsurface damage removal by reactive ion etching process. The results show that as the etching depth increases, the concentration of metal ions contamination in the subsurface of fused silica decreases significantly, the water contact angle of fused silica decreased, while homogeneity of adsorbed water molecules on fused silica surface increases, especially at higher humidity conditions. Furthermore, the nanohardness and reduced modulus of fused silica increases with the etching depth. These results will be helpful for optimizing the manufacturing and lifetime of fused silica in high energy laser systems. [ABSTRACT FROM AUTHOR]

ABSTRACT The aim of this study is to evaluate the free and adsorbed water flow in short logs of Eucalyptus urophylla and Corymbia citriodora clones. 40 cm long, short logs were extracted from the base of the trees. Three trees each of C. citriodora and E. urophylla (A and B clones) were used. 27 logs were debarked and dried to achieve stabilization of mass. Free water (FWFR), adsorbed water (AWFR) and total water (TWFR) flow rates, and basic density were calculated. FWFR was greater than TWFR, which was superior to AWFR. The B clone wood showed a higher FWFR value and a lower AWFR value when compared to the other materials. On the other hand, the A clone wood showed a higher TWFR than the other materials. The TWFR was inversely proportional to density.

Abstract Energy conversion and storage devices are considered to be potential candidates for application in health monitoring, smart-sensor and clean-energy harvesting. In this study, Li+ modified montmorillonite/poly(vinylidene fluoride-co-hexafluoropropylene) (MMT(Li)/PVDF-HFP) with energy conversion and storage abilities were prepared, and the effects of Li+ ions and adsorbed water on phase transformation as well as dielectric and piezoelectric performance were studied. MMT(Li)/PVDF-HFP composite film with 15 wt% MMT and 1.72 wt% H 2 O exhibited the good energy conversion and storage performances with high dielectric constant, generated current, open circuit voltage and holding time because of the Li+ polarization and β-phase nucleation by hydrogen bonds. Therefore, MMT modified by ion and H 2 O was an effective reinforce filler to prepare excellent energy conversion and storage film. We hope this modification method could inspire the performance optimization of other clay/polymer in the flexible electronic field. [ABSTRACT FROM AUTHOR]

A new unfrozen water characteristics curve (UWCC) model is proposed with explicit considerations of both capillarity and adsorption. Capillarity is considered to be dominant when the freezing of soil pore water occurs at higher temperatures, whereas the effects of adsorption are pronounced at lower temperatures. The proposed model is applied to predict UWCCs of silt at different initial void ratios and clay over a wide range of temperatures. It was found that the new model can capture the effects of void ratio on the UWCC. Moreover, the new model can better predict the UWCC over a wide range of temperatures. [ABSTRACT FROM AUTHOR]

Al doped ZnO nanoparticles (labeled as x% A-ZnO, x = 0.0, 0.5, 1.0, and 1.5) were synthesized by a simple sol-gel method, characterized and tested as photocatalysts for the degradation of a model compound under UV-light irradiation. Diffuse reflectance spectroscopy (DRS) and photoelectrochemical analysis have been performed to evidence their optical and electronic behavior. The structural features of the powders were highlighted by means of specific surface area (SSA) analysis, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and Raman spectroscopy. Al doping results in enhanced photocatalytic activity of the modified powders with respect to pure ZnO. In particular, the highest activity was achieved with the 1.0% A-ZnO sample. The presence of Al did not significantly change neither the optical absorption nor the electronic structure of the powders. In fact, the observed blue shift of the band gap and cathodic shift of the quasi Fermi level of the modified powders occurred only at a virtually negligible extent. On the other hand, the structural analysis evidenced that the enhanced photocatalytic activity may be ascribed to the important surface defectivity induced mainly by substitution of Zn 2+ by Al 3+ ions and to the deriving higher hydrophilicity of the Al doped samples. [ABSTRACT FROM AUTHOR]

The effect of the state of hydrated surface of the bulk oxide photocatalysts, TiO2, CeO2, and ZnO on the rate of UV-induced oxidation of CO with atmospheric oxygen was studied. The activity of dehydroxylated catalyst samples evacuated at temperatures of >350 °C toward CO photooxidation decreases in the series CeO2 > ZnO ≈ TiO2, while that of partially hydrated samples after pretreatment at 20 °C changes in the order TiO2 > ZnO ≥ CeO2 ≈ 0. According to the results, the difference in the photocatalytic activity toward CO oxidation on the dehydrated ZnO, TiO2, and CeO2 catalysts is attributable to different concentrations of oxygen vacancies, which are formed more readily after high-temperature treatment on ZnO and CeO2 and thus promote higher rate of CO photooxidation. Using a new technique for recording transmittance IR spectra, it was found that photoirradiation in the presence of adsorbed water and O2 gives peroxides and hydroperoxides, with their concentrations decreasing in the series TiO2 >> ZnO >> CeO2. Most likely, these species are active intermediates of CO photooxidation with oxygen in the presence of adsorbed water. The hydrophobization effect was detected upon TiO2 modification with zinc, resulting in removal of surface acid sites capable of adsorbing water. The TiO2 modification with zinc increases the activity of CO photooxidation with respect to the oxidation catalyzed by samples pretreated at low temperatures (20—60 °C). [ABSTRACT FROM AUTHOR]

The adsorption of water, pyridine, CO and CO on a commercial γ-AlO and a commercial amorphous silica alumina (ASA) cracking catalyst are reinvestigated by means of FTIR spectroscopy. It is concluded that the real active hydroxyl groups on γ-AlO are those absorbing at 3790, 3770 and 3730 cm and that they are significantly acidic. The strongest Lewis acid sites are identified as Nuclear Magnetic Resonance (NMR)-silent (or still undetected) tricoordinated Al, becoming tetracoordinated when interacting with basic adsorbates. More than one pyridine molecule may adsorb over such highly coordinatively unsaturated sites at high pyridine vapour pressure. It has also been confirmed that the existence of Brønsted acid sites sufficiently strong to protonate pyridine on ASA is its intrinsic property, not due to coadsorbed water. A 'stuffed amorphous silica' model is proposed for low-alumina ASA, where part of Al ions compensate the charge in-balance due to the substitution of Al for Si in a silica-like tetrahedral framework. Interstitial Al occupy 4-, 5- or 6-coordination interstices in the amorphous silica-like framework as do alkali cations in 'stuffed silicas' aluminosilicates. Such 'interstitial' Al ions when located accidentally in opened interstices exposed at the surface play the role of strong Lewis sites. When these ions are located near a silanol group, they increase the Brønsted acidity of the terminal silanols by neutralizing the negative charge produced by their dissociation when interacting with bases. [ABSTRACT FROM AUTHOR]

Structures of adsorbed water on anatase TiO 2 (1 0 1) were studied using diffuse reflectance near-infrared spectroscopy (DR-NIRS), demonstrating that water is a good NIR spectroscopic probe to show the absorption and the quantity of the absorbate. [Display omitted] • DR-NIRS was used to study the structure of absorbed water on TiO 2. • Continuous wavelet transform was used to enhance the resolution of the spectra. • Spectral features of the water absorbed on different sites were observed. • Water was proved to be a probe to show the absorption and the quantity of the absorbates. Investigating the structures of water on metal oxides is helpful for understanding the mechanism of the adsorptions in the presence of water. In this work, the structures of adsorbed water molecules on anatase TiO 2 (1 0 1) were studied by diffuse reflectance near-infrared spectroscopy (DR-NIRS). With resolution enhanced spectrum by continuous wavelet transform (CWT), the spectral features of adsorbed water at different sites were found. In the spectrum of dried TiO 2 powder, there is only the spectral feature of the water adsorbed at 5-coordinated titanium atoms (Ti 5c). With the increase of the adsorbed water, the spectral feature of the water at 2-coordinated oxygen atoms (O 2c) emerges first, and then that of the water interacting with the adsorbed water can be observed. When adenosine triphosphate (ATP) was adsorbed on TiO 2 , the intensity of the peaks related to the adsorbed water decreases, indicating that the adsorbed water is replaced by ATP due to the strong affinity to Ti 5c. Therefore, there is a clear correlation between the peak intensity of the adsorbed water and the adsorbed quantity of ATP. Water can be a NIR spectroscopic probe to detect the quantity of the adsorbed ATP. A partial least squares (PLS) model was established to predict the content of adsorbed ATP by the spectral peaks of water. The recoveries of validation samples are in the range of 92.00–114.96% with the relative standard deviations (RSDs) in a range of 2.13–5.82%. [ABSTRACT FROM AUTHOR]

• A theoretical SFCC model for saline soil is proposed and validated. • The unfrozen water content during two phase transition stages is well predicted. • Eutectic temperature is related to the initial solute concentration and saturation. Soil freezing characteristic curve (SFCC) characterizes the relationship between liquid water content and temperature in frozen soils, which is of significance in simulating the heat, moisture, and solute migration process in the hydrological cycle in cold regions. Soil freezing process of saline soils includes various stages including ice or salt crystallization and ice-salt eutectic. However, most SFCC models ignored the eutectic stage. Based on the framework of chemical potential equilibrium, a theoretical model is developed considering the ice-salt eutectic phenomenon in this study. The model can well predict the change in unfrozen water content in various stages for both low and high initial concentrations from the soil–water characteristic curve (SWCC). The applicability and accuracy of the model are well verified by the published data of the measured phase diagrams of bulk salt solution and SFCCs for different types of soils. The effects of soil type, initial solute concentration, and initial water content on soil freezing process and eutectic temperature are further analyzed using the theoretical model, which is in agreement with reported experimental results. The work provides a comprehensive view to understand the freezing characteristic of saline soils. [ABSTRACT FROM AUTHOR]

Crashed or dimensional rocks have been used as natural construction material, decoration stone or as material for artistic sculptures. Especially old historical towns not only in Slovakia have had experiences with use of stones for construction purposes for centuries. The whole buildings were made from dimensional stone, like sandstone, limestone or rhyolite. Pavements were made especially from basalt, andesite, rhyolite or granite. Also the most common modern construction material - concrete includes large amounts of crashed rock, especially limestone, dolostone and andesite.

IR spectroscopy combined with thermogravimetry was used to investigate the effect of the pretreatment temperature on the degree of coverage of the surface of oxide photocatalysts, TiO, ZnO, CeO, and Zn/TiO, with water. At room temperature, the amount of adsorbed water per unit area of photocatalysts in the air decreases in the row: ZnO ≥ CeO > TiO, whereas the temperature needed for complete removal of physically adsorbed water from the studied oxides decreases in the reverse order. Water is removed from the ZnO surface by evacuation at room temperature; in the case of CeO and TiO, it desorbs at 200 and 300 °С, respectively. The terminal OH groups on the oxide surface are the most strongly bonded with adsorbed water. In the zinc modified TiO, the terminal OH groups are firstly replaced by Zn cations, which causes both hydrophobization of the samples under atmospheric conditions and a decrease in the temperature at which physically adsorbed water is released from the surface. Evacuation of ZnO at 350 °C removes the surface oxygen and results in the generation of the surface defect sites. This causes strong absorption in the IR spectra in the region of 1000-4000 cm. The formation of surface defects probably causes the appearance of donor levels in the band gap. The energy of the transition of electrons from these levels to the conduction band corresponds to the energy of the IR radiation. After oxidation of such samples in O at 350 °C, strong absorption in the IR spectra disappears. [ABSTRACT FROM AUTHOR]

This study aims to reveal how water adsorbed on to a solid can influence its catalytic properties for transesterification in liquid phase. A commercial magnesium silicate was subjected to a range of thermal pretreatments and used for the transesterification of ethyl acetate with methanol. Conversion of ethyl acetate decreased with increasing pretreatment temperature, in direct relation to the release of the water content of the magnesium silicate. Thermogravimetric analysis, diffuse reflectance infrared Fourier transform (DRIFT), and 1H NMR spectroscopies revealed that physically adsorbed water had little influence on the reactivity. The water incorporated within the catalysts, however, which desorbs at higher temperatures, played a key role on the conversion. Calorimetry, in situ DRIFT spectroscopy, and 1H NMR characterization indicate that two kinds of active site exist. These are created from the water coordinated to magnesium located on the edge of the clay-like particles or in the defects present in the silicate layer, respectively. Their role could be to stabilize methanol deprotonated by basic Mg-OH groups, activate the ester, or help the departure of the alkoxyl moiety. [ABSTRACT FROM AUTHOR]

The adsorbed water influences significantly, the physical and mechanical properties of wood. In the present paper, the spatial distribution of adsorbed water in wood cell walls has been studied by α-Fourier transform infrared (α-FTIR) and confocal Raman spectroscopy. In situ µ-FTIR spectra were collected from three randomly selected areas in different cell wall regions, which were exposed to an environment with 0% to 96% relative humidity (RH). The water adsorption sites were easily detectable based on OH, C=O, and C-O group vibrations and it was shown that the adsorbed water concentration was not uniform in different regions. Confocal Raman spectroscopy images were collected from the cell corner (CC) and middle layer of the secondary wall (S2) and the non-uniformity of water distribution could also be confirmed by this approach. It was demonstrated that both α-FTIR and confocal Raman spectroscopy provide valuable information about the spatial distribution of adsorbed water in morphologically distinct cell wall regions. [ABSTRACT FROM AUTHOR]

• Quantitative evaluation the multiphase phase water by NMR-centrifugal method. • A novel methodology to re-evaluating the accurate multiphase water distribution. • Theoretical study of adsorbed and free phase water microscopic distributions. An in-depth understanding of multiphase water (adsorbed and free phase) distribution in coals is critical to the coalbed methane engineering application. However, the multiphase water quantitative characterization method, together with its microscopic mechanism still remains unavailable. This article proposed an innovative and more accurate methodology to characterize the multiphase water in coals by combining theory and experiment, which is applicable not only in water-saturated coals but also in the sub-saturated state. Firstly, traditional nuclear magnetic resonance (NMR)-centrifugal experiments were performed for six coals with strikingly different ranks to evaluate the experimental multiphase water distributions. Results show that the free water amounts significantly increase with increasing centrifugal pressure before stabilizing to a limiting value, similar to a Langmuir-like equation. An innovative modified multiphase water analysis model was established by integrating the centrifugation and typical pore structure parameters with the adsorption ratio equation. Results indicate that the adsorbed water density and mean adsorption thickness value as 1.59 g/cm3 and 0.63 nm, respectively. The estimated optimal surface relaxivities of coals range from 2.2 nm/ms to 5.2 nm/ms. The experimental estimated multiphase water NMR spectra are inconsistent with those from a theoretical model, leading to inaccurate analysis in the laboratory and field logging based only on experimental results. The multiphase water theoretical calculation method proposed in this article can be applied for quantitatively characterizing both the adsorbed/free water contents and its distributions in (un) saturated coals. [ABSTRACT FROM AUTHOR]