Saturated Water Vapor Research Articles

An experimental study of the solubility and speciation of thorium in chloride-bearing aqueous solutions at temperatures up to 250 °C

The solubility and speciation of Th in Cl-bearing solutions saturated in ThO2 was investigated experimentally at 150, 175, 200, 225 and 250 °C, and saturated water vapor pressure. At these experimental conditions (pH25°C < 3.8, mNaCl < 2.5), Th-chloride complexation is insignificant, and the solubility of Th is controlled by hydrolysis. The two main species in solution were identified as Th(OH)22+ and Th(OH)4° and formed via the reactions Th4++2OH-↔Th(OH)22+ and Th4++4OH-↔Th(OH)40. The logarithms of the formation constants determined for the first reaction are 23.91 ± 0.05, 24.79 ± 0.07, 25.78 ± 0.05, and 25.85 ± 0.05 for 175, 200, 225 and 250 °C, respectively, and 42.18 ± 0.06, 43.50 ± 0.07, 43.17 ± 0.08, and 43.74 ± 0.11 for the second reaction at the same temperatures. Formation constants could not be determined reliably for 150 °C. Extrapolations of our formation constants to 25 °C are in excellent agreement with the values determined at 25 °C by Neck and Kim (2001) and Ekberg et al. (2000). For natural systems buffered by thorianite (ThO2), the solubility determined in our study likely reflects a minimum, as the presence of additional ligands would lead to higher solubility.

Spatial Distribution of Sensible and Latent Heat Flux in the City of Basel (Switzerland)

Urban surfaces are a complex mixture of different land covers and surface materials; the relative magnitudes of the surface energy balance components therefore vary widely across a city. Eddy covariance (EC) measurements provide the best estimates of turbulent heat fluxes but are restricted to the source area. Land surface modeling with earth observation (EO) data is beneficial for extrapolation of a larger area since citywide information is possible. Turbulent sensible and latent heat fluxes are calculated by a combination of micrometeorological approaches (the aerodynamic resistance method, ARM), EO data, and GIS techniques. Input data such as land cover fractions and surface temperatures are derived from Landsat 8 OLI and TIRS, urban morphology was calculated from high-resolution digital building models and GIS data layers, and meteorological data were provided by flux tower measurements. Twenty-two Landsat scenes covering all seasons and different meteorological conditions were analyzed. Sensible heat fluxes were highest for industrial areas, railway stations, and areas with high building density, mainly corresponding to the pixels with highest surface-to-air temperature differences. The spatial distribution of latent heat flux is strongly related to the saturation deficit of vapor and the (minimum) stomatal resistance of vegetation types. Seasonal variations are highly dependent on meteorological conditions, i.e., air temperature, water vapor saturation deficit, and wind speed. Comparison of measured fluxes with modeled fluxes in the weighted source area of the flux towers is moderately accurate due to known drawbacks in the modeling approach and uncertainties inherent to EC measurements, particularly in urban areas.

A Thermodynamic Model of the Water–Rock Interaction under Hydrothermal Exposure of the Bazhenov Formation

Thermodynamic modeling of the hydrothermal exposure of the rocks of the Bazhenov Formation resulted in revealing the equilibrium mineral associations at 50–350°C and the pressure of saturated water vapor. The calculation results show that mineral parageneses varied slightly with the increase of temperature. Thus, zeolites were characterized by the stilbite–laumontite–wairakite series; kaolinite, pyrite, dolomite, and brannerite were replaced by montmorillonite and/or albite, pyrrhotite, calcite, and uraninite, respectively. The modeling results were confirmed in experiments.

WATER-ROCK INTERACTION THERMODYNAMIC MODELING WHILE HYDROTHERMAL EXPOSURE ON THE BAZHENOV FORMATION ROCKS

Equilibrium mineral assemblages at temperatures from 50 °C to 350 °C and pressure of saturated water vapor were established by the thermodynamic modeling of hydrothermal reaction on the Bazhenov Formation rocks. The calculation results show that the mineral parageneses vary slightly with the temperature increase: for zeolites stilbite-laumontite-wairakite row is typical, kaolinite is replaced by montmorillonite and/or albite, pyrite — by pyrrhotite, calcite — by dolomite, brannerite — by uraninite. The simulation results are confirmed by experimental data.

Shape fixation of compressed wood by steaming: a mechanism of shape fixation by rearrangement of crystalline cellulose

Japanese cedar wood specimens were compressed radially using saturated water vapor at 160 °C. Their shape recovery in hot water, cellulose crystallinity, and dynamic viscoelastic properties were measured. The compressed shape of the wood was fixed completely with 120 min of steam compression. In addition, the tensile strain of the elongated steam-compressed wood specimens was recovered almost completely upon immersion in hot water. The crystallinity and crystal width of cellulose in the compressed wood increased with increasing steaming duration, corresponding to the fixation of the compressed shape and the recovery of tensile strain. These results suggested that the recrystallization or co-crystallization of cellulose, i.e., the reformation of elastic members in the wood cell walls, caused shape fixation by steam compression. When a wood specimen was compressed at 25 °C, its dynamic Young’s modulus in the radial (R) direction (ER) decreased, while its mechanical loss tangent (tan δR) increased remarkably. However, upon subsequent steaming, the reduced ER began increasing and the enhanced tan δR began decreasing. These changes were explained by a hypothetical slip–cure model in which microfractures and slippage between or within microfibrils were cured by the rearrangement of cellulose under steaming.

Vapor Cartesian diver

The article proposes a new research object for a general physics course—the vapour Cartesian diver, designed to study the properties of saturated water vapour. Physics education puts great importance on the study of the saturated vapour state, as it is related to many fundamental laws and theories. For example, the temperature dependence of the saturated water vapour pressure allows the teacher to demonstrate the Le Chatelier’s principle: increasing the temperature of a system in a dynamic equilibrium favours the endothermic change. That means that increasing the temperature increases the amount of vapour present, and so increases the saturated vapour pressure. The experimental setup proposed in this paper can be used as an example of an auto-oscillatory system, based on the properties of saturated vapour. The article describes a mathematical model of physical processes that occur in the experiment, and proposes a numerical solution method for the acquired system of equations. It shows that the results of numerical simulation coincide with the self-oscillation parameters from the real experiment. The proposed installation can also be considered as a model of a thermal engine.

Environmental Significance of the Stable Isotopes in Precipitation at Different Altitudes in the Tuolai River Basin

Precipitation samples and meteorological data were collected simultaneously during individual precipitation events at Tuole station (3367 m a.s.l.) and Jiayuguan station (1658 m a.s.l.) in the Tuolai River Basin. A study of temporal variation, Local Meteoric Water Lines, and altitude change on precipitation stable isotopes was conducted. The relationships between precipitation stable isotopes and temperature, precipitation, average vapor pressure, and relative humidity were determined in order to explore the environmental significance of the stable isotopes at different altitudes in the middle reaches of the Qilian Mountains. The analysis indicated that the stable isotopes of the precipitation in Tuole and Jiayuguan station were characterized by pronounced seasonal variation, with Tuole having higher δ18O values in summer and autumn and lower δ18O values in spring and winter, while Jiayuguan displays higher δ18O values in spring and lower in other seasons. The d-excess was correlated negatively with δ18O, and the correlation coefficients between δ18O and d-excess decreased with increasing altitude due to weakening sub-cloud evaporation. The slope and intercept of the Local Meteoric Water Lines from Jiayuguan to Tuole rose significantly, showing an increasing trend from low altitude to high altitude. For the precipitation events above 10℃, δ18O of Tuole was positively correlated with the temperature, but the Jiayuguan results indicated the opposite. Sub-cloud evaporation weakened with high precipitation events in Jiayuguan. δ18O and d-excess were positively correlated with the average vapor pressure, which declined from Tuole to Jiayuguan. Since the water vapor pressure and saturated water vapor pressure increased, it was difficult to form precipitation with decreasing altitude. The local strong sub-cloud evaporation caused δ18O and δD was positive at low altitude, while the effect of moisture recycling is obvious, such that δ18O and δD are negative in high altitude areas. There is no significant positive correlation between the δ18O and the relative humidity of the precipitation in Jiayuguan, while Tuole displays an opposite pattern. The results of the study will provide a scientific basis for further study of precipitation isotopes in the Tuolai River basin.

Transport Rate of Liquid Water and Saturated Water Vapors across Polymer Proton-Exchange Membranes

Dependences of the transport rate of liquid water and saturated water vapor across commercial membranes (Nafion, MF-4SK) and proton-exchange membranes synthesized by the authors (PVDF, PP, UHMWPE, PTFE films modified with sulfonated polystyrene) on the membrane thickness have been studied. It has been found that at room temperature (17–25°C), the transport rate of liquid water and saturated water vapor across the membranes into an air stream hardly depends on the membrane type and thickness (60–240 μm), with the transport rate of saturated vapor being almost an order of magnitude below that of liquid water contacting one of the membrane surfaces. The fact that the flux of water and water vapor across the membrane does not depend on membrane thickness under conditions of maximum moistening suggests that the flow resistance is determined by the resistance at the feed and permeate interfaces. If one of the membrane surfaces is in contact with liquid water, the transport rate is equal to the rate of water removal from the permeate surface of the membrane; in the case of contact with saturated vapor, the transport rate is determined by the rate of water sorption from the vapor phase by the membrane. The results can be used to optimize the operation of fuel cells based on polymer proton-exchange membranes.

Study of the Hydration Process of Synthetic Preparation of Ettringite by Direct Addition of Aluminum Sulfate and Calcium Hydroxide

The stability of ettringite as high-watery mineral is highly dependent on the ambient temperature. Under standard laboratory conditions, onset of decomposition of this phase occurs at temperature of 80°C already and the theoretical temperature of the complete decomposition of ettringite is 180°C. Ettringite decomposition can occur at significantly different temperatures under humidity conditions other than the laboratory ones. Within the work verification of the possibility of synthetic preparation of ettringite by direct addition of aluminum sulfate, Al2(SO4)3·18H2O, and calcium hydroxide, Ca (OH)2, as an alternative method to the yeelimite hydration procedure was carried out. The stability of the resulting systems was examined in two different environments, namely in a laboratory environment and the environment of saturated water vapour. The phase composition of the samples was determined by X-ray diffraction (XRD) analysis, thermal analysis and scanning electron microscopy (SEM).

Shape recovery and anomalous swelling of steam-compressed wood by swimming ring-like expansion of cell lumina

To investigate the mechanism of shape fixation of steam-compressed wood, Japanese cedar wood specimens were compressed radially by 50% using saturated water vapor at 160 °C and observed during shape recovery in different liquids, including water and dimethyl sulfoxide (DMSO). Shape recovery was evaluated based on the dimensional changes in wet conditions (SRw) and those in dry conditions (SRd). SRw in DMSO was significantly greater than that in water, but this recovery observed in DMSO was not recognized in SRd. The contradiction arose from significant reversible cellular deformation: the compressed cells were reversibly expanded with the swelling of the cell wall, and this swimming ring-like cellular deformation increased SRw in DMSO. At room temperature, the SRd values in various liquids were closely connected to the swelling of the wood cell walls, rather than to the degree of softening. This suggested that the plastic expansion of cells, as well as the softening of the wood cell walls, caused the shape recovery of compressed wood. This mechanism was qualitatively expressed by an elasto-plastic model equipped with an inflator representing the swimming ring-like expansion of the cell lumina.

Spontaneous Synthesis of Highly Crystalline TiO2 Compact/Mesoporous Stacked Films by a Low-Temperature Steam-Annealing Method for Efficient Perovskite Solar Cells.

Highly crystalline TiO2 nanostructured films were synthesized by a simple steam treatment of a TiCl4 precursor film under a saturated water vapor atmosphere at 125 °C, here referred to as the steam-annealing method. In a single TiO2 film preparation step, a bilayer structure comprising a compact bottom layer and a mesoporous surface layer was formed. The mesoporous layer was occupied by bipyramidal nanoparticles, with a composite phase of anatase and brookite crystals. Despite the low-temperature treatment process, the crystallinity of the TiO2 film was high, comparable with that of the TiO2 film sintered at 500 °C. The compact double-layered TiO2 film was applied to perovskite solar cells (PSCs) as an electron-collecting layer. The PSC exhibited a maximum power conversion efficiency (PCE) of 18.9% with an open-circuit voltage ( VOC) of 1.15 V. The PCE and VOC were higher than those of PSCs using a TiO2 film formed by 500 °C sintering.

Solubility of MoO3 in Aqueous Acid Chloride-Bearing Solutions at 573 K

This study reports the measurements of the solubility of crystalline molybdenum trioxide, MoO3, in aqueous solutions of the mixture HCl–HClO4–NaCl (up to 1 m of chloride ion) at 573.2 K and pressures close to the saturation water vapor pressure by the autoclave method with the chemical analysis of quenched solutions. In total, there are 75 data points. The data treatment shows that the most probable chloride species of Mo(VI) in the studied solutions is MoO2(OH)2Cl– (the coordinated water is omitted), which agrees with the literature extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) spectra studies of speciation of Mo(VI) in chloride solutions at elevated temperatures. For the solubility reaction MoO3(cr) + H2O(l) + Cl– = MoO2(OH)2Cl–, log10 K° = −(0.87 ± 0.2).

Reduction of moisture sensitivity of PbS quantum dot solar cells by incorporation of reduced graphene oxide

PbS nanocrystals are an important narrow-gap material for solar cells and photodetectors. Nevertheless, their application may be limited because device performance can be affected by atmospheric conditions. Indeed, the presence of oxygen and/or water can degrade the active layers, possibly leading to device failure. Strategies to address this issue are therefore actively explored. Here we report a solution-processed PbS quantum dot solar cell, consisting of a PbS-silane functionalized reduced graphene oxide (PbS-rGO) layer on top of the PbS absorber film, which enhances device stability, especially when the solar cells are exposed to moisture. Power conversion efficiency (PCE) measurements demonstrate a slower degradation under continuous illumination for solar cells with PbS-rGO. When storing the samples under saturated water vapor, differences are even more remarkable: with PbS-rGO the solar cells essentially maintain their initial PCE, while the PCE of the PbS reference devices is reduced by 50% after 5 days. Scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopy reveal the damage to the PbS films and the formation of PbSOx crystals in the PbS reference devices. Such crystals are not observed in the PbS-rGO devices, further supporting the importance of the PbS-rGO barrier layer.

Corrosion of SiC layers on coated zirconia particles in wet atmosphere

Properties of SiC coating layer in the postulated accident condition of air and water ingress is crucial to the in-pile safety of tristructural-isotropic (TRISO) coated fuel particles of high temperature gas-cooled reactors (HTR). Particles of ZrO2 kernels coated with low-density pyrolytic carbon buffer layer, high-density pyrolytic carbon layer and SiC layer fabricated by fluidized-bed chemical vapour deposition (FBCVD) were used to simulate real fuel particles in this research. The coated particles were tested at 1673 K in a certain flowing air with different water content between 0 and 100 g/m3 for 10 h. Analysis results show that the corrosion reaction took place mainly on the outer surface of SiC layer with changing infiltration depth according to the flowing gas compositions. Steam content was controlled according to the relationship between saturated water vapour pressure and environment temperature. SiO2 layer was the main product formed on the surface with thickness increase from 1.5 µm to 3 µm along with the content of water vapour in air. Formation of two types of micro-cracks after oxidation are observed: micro-cracks on spherulitic SiO2 and penetrating micro-cracks on flat SiO2. Micro-stress generation mechanism is illustrated. Three are also some bubbles are observed either in SiO2 layer or between SiO2 and SiC layers. Results showed that no fracture occurred in the SiC layer after wet oxidation.

Analyzing reversible changes in hygroscopicity of thermally modified eucalypt wood from open and closed reactor systems

Eucalyptus nitens was thermally modified in either an open or a closed reactor system at different temperatures and water vapor pressures. Reversible changes in equilibrium moisture content (EMC) and volumetric swelling (Smax) were analyzed during cycles that included repeated conditioning at 20 °C/65% RH, water-soaking and vacuum-drying at room temperature. These cycles partially diminished the reduction in EMC and Smax measured directly after the modification process. The recovery of drying-related annealing effects of amorphous polymers was considered the main effect during water-soaking cycles of wood from the open reactor system, while the removal of the cell wall bulking effect was the main effect in the wood modified in the closed system in nearly saturated water vapor. Water-soaking cycles also changed the dynamic vapor sorption behavior to a considerable extent, leading to a lower reduction in EMC by thermal modification over the entire RH range measured. Exposure of the samples to 95% RH during the dynamic vapor sorption measurements was incapable of removing reversible effects to the same extent as repeated water soaking.

Computer Simulation of the Cathode Active Layer in Hydrogen–Oxygen Fuel Cell with Polymer Electrolyte: The Nature of the Overall Current Variations

Full computer simulation of the cathode structure in hydrogen–oxygen fuel cell with polymer electrolyte is performed. Both transport, support grains (agglomerates of carbon particles onto whose surface Pt-catalyst is deposited), and the current generation in active layer are simulated. The active layer operation in potentiostatic mode is studied. The effect of variations of the active layer and the fuel cell temperature (Ts and Т, respectively) on the cathode overall current I and the support grain flooding with water is calculated. The changes in the temperature difference Ts–Т was shown for the first time, experimentally and by the simulation, to generate variations of I and the degree of the support grain flooding with water. In particular, with the increasing of Ts–Т the current I increased, whereas the support grain flooding with water decreased; and vice versa, with the decreasing of Ts–Т the current I drops down, while, the support grain flooding with water grows. An explanation of the phenomena is presented, which takes account of structure of the support grains in which О2 reduction and Н2О generation occur. There exist intrinsic channels for protons and О2 molecules transportation to the catalyst. Water releasing in the support grains is able to fill partially or even entirely the gas pores through which oxygen is supplied to the platinum. As a result, the current generated in the support grains can drop down significantly; at the same time, the value of I also drops down. The degree of the support grainfilling with water is determined by two processes, namely, the flooding and draining. The source of flooding is the current generation; that of draining, the water saturated vapor diffusion and water filtration in nanopores. The lower cathode potential, the higher the flooding rate, whereas the water removal rate grows or drops down with the increasing of decreasing of the temperature difference Тs–Т, respectively. Thus, the temperature difference variations naturally lead to those of the quantity I.

Dimerization Degree of Water Molecules, Their Effective Polarizability, and Heat Capacity of Saturated Water Vapor

The properties of water vapor have been studied. The main attention is focused on the physical nature of the effective polarizability of water vapor and the heat capacity of water vapor at a constant volume, with a proper modeling of those parameters being a good test for a correct description of the dimer concentration in various approaches. Thermal vibrations of water dimers are found to be the main factor governing the specific temperature dependences of those characteristics, and the normal coordinates of dimer vibrations are determined. Fluctuations of the dipole moments of dimers and their contribution to the dielectric permittivity of water vapor are considered in detail. The contribution of the interparticle interaction to the heat capacity is taken into account. By analyzing the effective polarizability and the heat capacity, the temperature dependence of the dimer concentration at the vapor-liquid coexistence curve is determined. The noticeable dimerization in saturated water vapor takes place only at temperatures T/Tc &gt; 0.8, where Tc is the critical temperature.

Effect of Oxidating Treatment on the Electrical Properties of Reduced LiNbO3 Crystals

The effect oxidizing annealing has on the electrical properties of nominally pure congruently grown LiNbO3 crystals is investigated via impedance spectroscopy. A set of samples is preliminarily reduced in saturated D2O or H2O vapor. It is shown that reducing annealing in saturated water vapor at T = 773 K results in partial deprotonation of LiNbO3 crystals. It is assumed that such annealing does not change the charge state of impurity ions with variable valence.

A Review on Water Vapor Pressure Model for Moisture Permeable Materials Subjected to Rapid Heating

This paper presents a comprehensive review and comparison of different theories and models for water vapor pressure under rapid heating in moisture permeable materials, such as polymers or polymer composites. Numerous studies have been conducted, predominately in microelectronics packaging community, to obtain the understanding of vapor pressure evolution during soldering reflow for encapsulated moisture. Henry's law-based models are introduced first. We have shown that various models can be unified to a general form of solution. Two key parameters are identified for determining vapor pressure: the initial relative humidity and the net heat of solution. For materials with nonlinear sorption isotherm, the analytical solutions for maximum vapor pressure are presented. The predicted vapor pressure, using either linear sorption isotherm (Henry's law) or nonlinear sorption isotherm, can be greater than the saturated water vapor pressure. Such an “unphysical” pressure solution needs to be further studied. The predicted maximum vapor pressure is proportional to the initial relative humidity, implying the history dependence. Furthermore, a micromechanics-based vapor pressure model is introduced, in which the vapor pressure depends on the state of moisture in voids. It is found that the maximum vapor pressure stays at the saturated vapor pressure provided that the moisture is in the mixed liquid/vapor phase in voids. And, the vapor pressure depends only on the current state of moisture condition. These results are contradictory to the model predictions with sorption isotherm theories. The capillary effects are taken into consideration for the vapor pressure model using micromechanics approach.

Synthetic Preparation and Properties of Ettringite

This paper deals with the verification of the possibility of preparing synthetic ettringite in a way of direct addition of aluminum sulfate and calcium hydroxide as an alternative to the hydration of yeelimite. The stability of the resulting system was studied using the X-ray diffraction (XRD) and differential thermal analysis (DTA) in two different environments, namely in a laboratory environment and the environment of saturated water vapour. The evaluations of X-ray diffraction analysis and thermal analysis show that in the ettringite sample stored in the laboratory environment, evaporation of molecular water and subsequent transformation of ettringite into metaettringite or monosulfate can occur over time. Conversely, exposition of saturated water vapour environment can lead to saturation of the system by free calcium ions due to the slow dissociation of calcium carbonate, and thereby increase the amount of ettringite at the expense of gypsum and aluminum amorphous phase. To verify the above, it is recommended long-term monitoring of samples exposed in monitored environments.