Range Of Water Vapor Pressures Research Articles

A limiting current oxygen sensor with 8YSZ solid electrolyte and (8YSZ)0.9(CeO2)0.1 dense diffusion barrier

A series of (8YSZ)1-x(CeO2)x (0 ≤ x ≤ 0.3) materials are synthesized by co-precipitation. Both crystalline structure and electrical conductivity of material are detected. (8YSZ)1-x(CeO2)x (0 ≤ x ≤ 0.3) belongs to cubic phase and (8YSZ)0.9(CeO2)0.1 is provided with the highest electrical conductivity. Select 8YSZ as solid electrolyte and (8YSZ)0.9(CeO2)0.1 as dense diffusion barrier to prepare an oxygen sensor by Pt paste bonding method. Limiting current plateau of the sensor is observable at 2% oxygen concentration and at 720–900 °C, and logarithm of the limiting current (log IL) plays a linear relationship to 1000/T. Limiting current of the sensor is observable at 850 °C and 2–14% oxygen concentration, which is linearly related to the oxygen concentration. The limiting current of the sensor does not vary significantly in the range of water vapor pressure (p(H2O)) 280.66–2268.63 Pa and in the range of carbon dioxide concentration 0–90%, respectively. The limiting current of the sensor does not decay in the oxygen concentration of 2% at 850 °C during the detection time of 120 h.

Modeling of the lithium hydride hydrolysis under low relative humidity

A reactional mechanism describing the hydrolysis of lithium hydride (LiH) under moist atmosphere is proposed and modeled. It involves the formation of lithium oxide (Li2O) at low vapor pressure and both lithium oxide and lithium hydroxide (LiOH) at higher vapor pressures, with diffusion of water in these layers. A numerical model based on this mechanism is implemented with COMSOL Multiphysics to simulate the hydrolysis of LiH particles in open system (constant water vapor pressure). Kinetic parameters such as rate constant of reactions and diffusion coefficient of water in Li2O and LiOH are first fitted against experimental data. The best agreements are obtained when the diffusion coefficient of water is 10 times higher in LiOH than in Li2O. The resulting model accurately predicts the hydrolysis rates experimentally measured for a wide range of water vapor pressures (0.3–17 Pa). The hydrolysis mechanisms are compatible with a Li2O production limited by water diffusion and a LiOH production governed by the kinetics. Finally, simulation suggest that the thickness of the Li2O layer does not depends much on the water vapor pressure whereas that of LiOH increases drastically at high water vapor pressures.

Laboratory study of adsorption and deliquescence on the surface of Mars

A sample of the zeolitic mineral chabazite was subjected to a range of water vapor pressures and temperatures found on present day Mars. Laser Raman scattering was applied to detect the relative amounts of water and carbon dioxide adsorbed by the sample. Results show that zeolites are capable of adsorbing water from the atmosphere on diurnal time scales and that Raman scattering spectroscopy provides a promising method for detecting this process during a landed mission. When the water vapor pressure and temperature were sufficiently low, the zeolite sample also adsorbed carbon dioxide, resulting in the simultaneous adsorption of water and carbon dioxide on the surface mineral grains. Additional experiments were carried out using a mixture of magnesium perchlorate and chabazite. The sample of mixed surface material remained visually unchanged during water adsorption, but was found to darken during deliquescence.

Estimation of Fracture Toughness of Anisotropic Rocks by Semi-Circular Bend (SCB) Tests Under Water Vapor Pressure

In order to investigate the influence of water vapor pressure in the surrounding environment on mode I fracture toughness (K Ic) of rocks, semi-circular bend (SCB) tests under various water vapor pressures were conducted. Water vapor is one of the most effective agents which promote stress corrosion of rocks. The range of water vapor pressure used was 10−2 to 103 Pa, and two anisotropic rock types, African granodiorite and Korean granite, were used in this work. The measurement of elastic wave velocity and observation of thin sections of these rocks were performed to investigate the microstructures of the rocks. It was found that the distribution of inherent microcracks and grains have a preferred orientation. Two types of specimens in different orientations, namely Type-1 and Type-3, were prepared based on the anisotropy identified by the differences in the elastic wave velocity. K Ic of both rock types was dependent on the water vapor pressure in the surrounding environment and decreased with increasing water vapor pressure. It was found that the degree of the dependence is influenced by the orientation and density of inherent microcracks. The experimental results also showed that K Ic depended on the material anisotropy. A fracture process was discussed on the basis of the geometry of fractures within fractured specimens visualized by the X-ray computed tomography (CT) method. It was concluded that the dominant factor causing the anisotropy of K Ic is the distribution of grains rather than inherent microcracks in these rocks.

A Dependence on Water Content of Bactericidal Efficiency of Gamma-Radiation

Gamma irradiation of Bacillus megaterium spore samples of different water content was carried out at 22 deg in the absence of oxygen. To avoid lethal damage from postirradiation oxygen effect, all samples were given an anoxic postirradiation soaking with liquid water. Surviving fractions based on colony counts gave exponential dose/survival curves that were used as a measure of radintion lethal efficiency. The equilibrinm water vapor pressure range tested was from 5 x 10-4 to 21 torr. In changing from a condition in which spores are driest to one in which they are in equilibrium with water vapor at a partial pressure equivalent to 100 percent relative humidity, the lethal efficiency of the gamma radiation increases by about 35 percent.

Sensitive coating for water vapors detection based on thermally sputtered calcein thin films

In this paper the adsorption properties of thermally sputtered calcein thin films towards water and other polar molecules vapors are studied by different characterization techniques: quartz crystal microbalance, surface plasmon resonance and visible spectroscopy. Sensitivity of calcein thin films to water vapors resulted much higher as compared with those of a number of dyes whose structure was close to that of calcein. All types of sensors with calcein coatings have demonstrated linear concentration dependences in the wide range of water vapor pressure from low concentrations up to 27,000 ppm (close to saturation). At higher concentrations of water vapor all sensors demonstrate the abrupt increase of the response (up to two orders). A theoretical model is advanced explaining the adsorption properties of calcein thin films taking into account their chemical structure and peculiarities of molecular packing. The possibility of application of thermally sputtered calcein films in sensing technique is discussed.

Varenicline L-tartrate Crystal Forms: Characterization Through Crystallography, Spectroscopy, and Thermodynamics

This research utilized crystallographic, spectroscopic, and thermal analysis data to assess the thermodynamic stability relationship between the three known crystal forms of Varenicline L-tartrate. Of the two anhydrous forms (Forms A and B), Form B was determined to be the stable form at 0 K based on its calculated true density, hydrogen bonding in the crystal lattice, and application of the IR rule. Form A has a higher melting point and higher solubility at room temperature as compared to Form B, indicating that these forms are enantiotropically related. Application of the eutectic-melting method enabled accurate determination of the transition temperature (63 degrees C), with Form B as the stable anhydrous form at room temperature. The stability relationships between the anhydrous polymorphs and the monohydrate (Form C) were assessed through exposure of the anhydrous forms to a range of water vapor pressures at room temperature. A phase boundary was identified, with the monohydrate being the thermodynamically stable form above critical water activity values of 0.85 and 0.94 for Forms A and B, respectively. These results provide a better understanding of the form stability as it relates to normal manufacturing and storage conditions for the active pharmaceutical ingredient and drug product.

Influence of Water Vapor Pressure on Superconducting Properties of YBCO Film by TFA-MOD

We fabricated YBa2Cu3O7−x (YBCO) films on LaAlO3 (LAO) substrates using metal organic deposition of precursor solutions containing metal trifluoroacetates (TFA-MOD). The effect of water vapor pressure on the microstructure, degree of texture, and critical current of prepared YBCO films was evaluated. The firing process was performed in the water vapor pressure range from 7 to 31 kPa. According to the results of the XRD, SEM and X-ray ω scan analyses, the causes of critical properties’ change with the different water pressure were explained. The YBCO film prepared at the lower water pressure showed the low critical current because of the a–b axis grain. The films fired at 20 kPa showed the highest critical current of 3.8 MA/cm2.

Differential Water Sorption Studies on Kevlar 49 and As-Polymerized Poly(p-phenylene terephthalamide): Determination of Water Transport Properties

Water vapor sorption experiments have been conducted on Kevlar 49 at 30 degrees C over a range of water vapor pressures in 0-90% of saturation and on the as-polymerized form of the material at 30, 45, and 60 degrees C over a series of water vapor pressures of 0-60%, 0-25%, and 0-15%, respectively. For each of the differential steps in water vapor pressure, dynamic uptake curves were generated and analyzed according to a number of different mathematical models, including Fickian, Coaxial cylindrical, and intercalation models. The intercalation model was demonstrated to be the most successful model and considered two time-scales involved in the diffusion process, i.e., a penetrant-diffusive time-scale and a polymer-local-matrix-relaxation time-scale. The success of this model reinforces previously reported adsorption and desorption isotherms which suggested that water may penetrate into the surface layers of the polymer crystallite through a process known as intercalation.

ＳＣＢ試験による水蒸気環境下における岩石の破壊じん性の評価

The influence of water vapor pressure of surrounding environment on fracture toughness of rock is clarified, based on the results of a series of semi-circular bend (SCB) test under various water vapor pressures. The rocks used in the test are Kumamoto andesite and Kunnum basalt, and the range of water vapor pressure is from 10-3 to 103 Pa. The results obtained in this paper are summarized as follows: 1) Elastic modulus at 60% of maximum load depends on water vapor pressure, and decreases with increasing water vapor pressure.2) Fracture toughness depends on water vapor pressure, and decreases with increasing water vapor pressure. The tendency of influence of water vapor pressure on fracture toughness is the same as that on uniaxial compressive strength or tensile strength. The relation between fracture toughness and water vapor pressure can be represented as:KIC=βp-mwhere β is a constant and -m is the slope of the approximated line on the logarithmic graph. The value m is 0.013 for Kumamoto andesite and 0.012 for Kunnum basalt, respectively.3) Based on above results for the SCB test, models for load-displacement curve and for relation between crack velocity and stress intensity factor are suggested.4) The time until fracture was calculated under the assumption of the crack velocity V= αKIn and the above equation, where α is a constant and n is stress corrosion index. It is shown that the rock mass of large n and small m should be selected to assure the stability for long term in spite of change in surrounding water vapor environment.

Isothermal section of the Na 0.3CoO 2[sbnd]H 2O phase diagram at 22 °C from 11 to 100% relative humidity

An isothermal section of the Na 0.3CoO 2 H 2O system phase diagram at 22 °C from 11 to 100% relative humidity is presented. The superconducting Na 0.3CoO 2⋅1.2H 2O phase is stable at a relative humidity (RH) higher than 30%; Na 0.3CoO 2⋅0.6H 2O is the stable phase at RH below 30%. The unit cell parameters and temperature of superconducting transition of Na 0.3CoO 2⋅1.2H 2O do not depend on relative humidity. The Na 0.3CoO 2⋅1.2H 2O and Na 0.3CoO 2⋅0.6H 2O hydrates are line phases and have a constant water content over the water vapor pressure range of their stability.

Influence of Moisture on Ultra‐High‐Temperature Tensile Creep Behavior of in Situ Single‐Crystal Oxide Ceramic Alumina/Yttrium Aluminum Garnet Eutectic Composite

Tensile creep tests were conducted for an in situ single‐crystal alumina/yttrium aluminum garnet (Al2O3/Y3Al5O12 (YAG)) binary system eutectic composite at temperatures between 1773 and 1873 K in air and in a moist environment having a water‐vapor pressure range of 0.06–0.6 MPa, under a constant tensile stress range of 100–160 MPa. The Al2O3/YAG eutectic composite exhibited a stress exponent of 8–13, indicative of tensile creep behavior characterized by a dislocation back‐stress mechanism. Water‐vapor pressures ≤0.4 MPa led to a significant acceleration of creep rates as a result of enhanced dislocation mobility in the Al2O3 and YAG phases.

Water Vapor Transmission Rates and Sorption Behavior of Chitosan Films

ABSTRACT: This study measured the water vapor transmission rates (WVTR) and moisture sorption of chitosan films over a range of water vapor pressures at 25 °C. Films of a constant thickness were made using chitosan with 3 levels of deacetylation. Films were tested at test relative humidity (RH) difference between RH values of 84%, 75%, 69%, 53%, 43%, 33%, 23%, 11%, and 0 at 25 °C using ASTM F1249‐90 or ASTM E 96‐80. The equilibrium moisture content in the films ranged from 3.7% to 31.8% (dry basis) corresponding to 11% to 84% RH. WVTRs of films increased with increase in water vapor pressure. The mean WVTR ranged from 6.7 to 1146 (g/m2/d) over the range of water vapor pressure from 2.68 (11% RH) to 19.9 mmHg (84% RH). The percentage of deacetylation of chitosan films and the viscosity of the cast solution did not have an effect on the WVTR properties of chitosan films.

Influence of physisorbed water molecules on the dynamics of domain wall in an amorphous ferromagnet

It was found that physisorbed water molecules affect the near-surface dynamics of a 180° domain wall in an amorphous FeCuNbSiB ferromagnet. In the range of water vapor pressures 400–1300 Pa, the oscillating domain walls suffer enhanced damping in the near-surface region and reduce their relaxation frequency from 10 to 4 kHz. This effect is explained by the influence of surface magnetic defects arising due to the pressure produced by the clusters of physisorbed water molecules on the walls of micropores at the magnet surface.

Isotopic Water Handling and Hydrogen Isotope Recovery for Fusion Application by Using the Zr(V0.5Fe0.5)2Alloy—I: Sorption and Role of Hydrogen and Oxygen in the Batch Conversion Method

Experimental investigation of the reaction of light and heavy water vapors with a metallic alloy and the release of hydrogen by batch-mode conversion with a Zr(V{sub 0.5}Fe{sub 0.5}){sub 2} getter is presented. The dependence of cracking of water vapor on the alloy temperature and water vapor pressure is studied. The roles of initial as well as increasing concentrations of hydrogen and oxygen in the alloy are delineated. The conversion rate constant is observed to shift from being surface dissociation process-dependent to bulk diffusion process-dominated during the conversion process. Hydrogen sorption in the alloy and its release during the batch conversion of water vapor, which assumes considerable significance from the perspective of recovering tritium as fuel gas from tritiated water waste, are discussed based on the studies performed that maintained the getter at various temperatures in the range of 100 to 400{degree}C and over a water vapor pressure range of 50 to 500 Pa, with various hydrogen and oxygen concentrations in the getter alloy. 28 refs., 13 figs., 1 tab.

Effect of Hydrogen‐Water Atmospheres on Corrosion and Flexural Strength of Sintered α‐Silicon Carbide

Sintered α‐SiC was exposed for 10 h to H2 containing various partial pressures of H2O (PH2O from 5×10−6 to 2×10−2 atm; 1 atm≅105 Pa) at 1300° and 1400°C. Weight loss, surface morphology, and room‐temperature flexural strength were strongly dependent on PH2O. The strength of the SiC was not significantly affected by exposure to dry H2 at a PH2O of 5×10−6 atm; and following exposure at PH2O >5×10−3 atm, the strength was even higher than that of the as‐received material. The increase in strength is thought to be the result of crack blunting associated with SiO2 formation at crack tips. However, after exposure in an intermediate range of water vapor pressures (1×10−5<PH2O <1×10−3 atm), significant decreases in strength were observed. At a PH2O of about 1×10−4 atm, the flexural strength decreased approximately 30% and 50% after exposure at 1300° and 1400°C, respectively. The decrease in strength is attributed to surface defects caused by corrosion in the form of grain‐boundary attack and the formation of pits. The rates of weight loss and microstructural changes on the exposed surfaces correlated well with the observed strength changes.

Humidity‐Sensitive Characteristics of La3+‐Doped and Undoped SrSnO3

The humidity‐sensitive characteristics of La3+‐doped and undoped specimens were investigated at 400°C as a function of water vapor pressures. The conductivities of the specimens increased about one order of magnitude over the entire water vapor pressure range by the partial substitution of La3+ ions for Sr2+ in , accompanied by an increase in the humidity sensitivity. The origin of the increased sensitivity is discussed based on both changes in the defect structure of the specimens and in the behavior of chemisorbed water on the specimens. Furthermore, a sensing mechanism of a semiconductive humidity sensor is presented.

Effect of water on monetite synthesis in the solid state

Synthesis of calcium hydrogen phosphate CaHPO 4 can be carried out with a milling apparatus into which solid calcium dihydrogen phosphate Ca(H 2PO 4) 2.H 2O and tricalcium phosphate Ca 3(PO 4) 2.1/6H 2O mixtures are introduced. The effect of water vapor pressure P H 2O on this reaction has been investigated. At a given temperature (60°C) the curves of degree of conversion as a function of milling time depend on P H 2O . Formation of brushite CaHPO 4.2H 2O during the course of reaction can be noted for a particular range of water vapor pressure. If some amounts of brushite are added to the initial mixture, the kinetics of the reaction developed under water vapor are increased. Experiments on the evolution of products after a milling treatment give evidence of the important dependence of the reaction rate on water vapor pressure.

Permeation of water vapor through cellulose triacetate membranes in hollow fiber form

AbstractA modification of the carrier gas method for measuring permeability of a hollow fiber to a vapor is described with particular application to water vapor permeation through asymmetric cellulose triacetate in hollow fiber from. Conventional methods are inadequate because the high flux of permeation vapor combined with its low pressure on the permeate side and the small diameter of the fiber lead to an excessive buildup of pressure in the permeate stream—in some cases so great as to render much of the fiber length ineffective. The method described in this paper involves the permeation from the outside to the inside of the fiber of a binary mixture consisting of the water vapor and a fairly highly permeable carrier (helium). There is a significant pressure drop along the fiber, but a theoretical treatment is presented to take this into account and to permit a determination of the vapor permeability. Experiments at 35°C over a range of water vapor pressures up to 1.7 cm Hg gave a water flux of 9 × 10−3 cc(S.T.P.)/cm2‐sec‐cm Hg, with an apparent slight decrease with increasing pressure. Over the same range of water vapor pressure the helium flux decreased from 2.3 × 10−4 to 1.85 × 10−4 cc(S.T.P.)/cm2‐sec‐cm Hg.

Mechanism of Adhesion due to Adsorbed Water Vapor an Powder Particles

Adhesive forces generated at a contact point between spherical and plate specimens made of the same material due to water vapor adsorption on them were measured for four samples by using an electrobalance. The samples used here are commercial soda-lime glass bead, granulated urea and potassium halides, i.e. KCl and KBr. The values of the adhesive forces were collated with the amounts of adsorbed estimated from adsorption isotherms of water vapor on the above particle samples.The adhesive forces appeared at relative water vapor pressures of 0.25, 0.30, 0.30 and 0.17 for the glass bead, the granular urea, KCl and KBr, respectively. At this time, the thicknesses of adsorbed water layers were less than two layers for all the samples. Concerning the above results, this adhesive force can not be a binding-force due to a liquid bridge formed near the contact point. Therefore, the force which occurred in the early stage of a caking process is considered to be generated by the hydrogen bond induced between the two samples being attached with water layers. On the other hand, the force which increases considerably in high water vapor pressure range will be due to a liquid bridge between the two specimens. Moreover, it is concluded that the adsorbed water molecules less than 2 or 3 layers are influenced by surface properties of the solid, whereas the adsorbed more than 4 or 5 layers is no longer influenced from the solid surface. Thus, multi-layers of water molecules are thought to acquire an inherent property as the liquid water.