Individual Diffusion Coefficients Research Articles

One-step desilication-recrystallization towards enhanced diffusion for Ni/ZSM-5-catalyzed n-hexane hydrogenative isomerization

The hydrogenative isomerization of n-alkanes to their branched isomers over bifunctional catalysts, an effective approach for green gasoline and diesel production, has gained increasing interests in the petrochemical industry. A rational strategy for catalyst development has been proposed and demonstrated with a more favorable mass transfer of isomerization products. Such strategy comprises consecutive desilication/recrystallization upon the parent ZSM-5 zeolite, which generates a hierarchical porous structure. The following incorporation of Ni species ensures the proximity of the metallic and protic active sites, which catalyze the dehydrogenation/hydrogenation and skeletal isomerization steps, respectively. The above structural features of the new Ni/ZSM-5-DR catalyst have been evidenced by various characterization methods. Regarding the changes in the reaction network, the intrinsic rate constant and activation energy are not influenced by the new porous structure, but the mass transfer property of different reagents shows significant distinction. It is further supported by the overall apparent kinetic behavior that diffusion-limited region has been shifted towards higher temperatures after the introduction of the new porous structure. The results of individual diffusion coefficients and overall product distribution provide final evidence of the proposed scenario. As a result, the catalyst development leads to the preferred isomerization product distribution with high selectivity.

CO2 diffusion in dry and hydrous leucititic melt

Abstract. Using the diffusion couple technique, diffusion of CO2 in a leucititic melt from the Colli Albani Volcanic District in Italy was investigated at temperatures between 1200 and 1350 ∘C in an internally heated pressure vessel at 300 MPa. To examine the effect of dissolved H2O in the melt, experiments were performed for a nominally dry melt (0.18 ± 0.03 wt % H2O) and for a hydrous melt containing 3.36 ± 0.28 wt % H2O. Diffusion experiments were run for 40 to 120 min and terminated by rapid quench. CO2 concentration profiles were subsequently measured via attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and fitted with error functions to obtain individual diffusion coefficients. For the anhydrous and hydrous sample series, seven diffusion coefficients were determined each. Diffusivity was found to increase exponentially with temperature for both melts following an Arrhenius behaviour. The Arrhenius equation for the nominally dry leucititic melt is described by log⁡DCO2=-1.44(±0.24)⋅10000T-1.95(±1.59), where DCO2 is the diffusion coefficient in m2 s−1 and T is the temperature in K. In the experimental temperature range, H2O has an accelerating effect on CO2 diffusion. At 1200 ∘C, diffusivity increases from 1.94 × 10−12 m2 s−1 in the dry melt to 1.54 × 10−11 m2 s−1 in the hydrous melt. The Arrhenius equation for the leucititic melt containing 3.36±0.28 wt % H2O is given by log⁡DCO2=-1.09(±0.30)⋅10000T-3.41(±1.99). The activation energies for CO2 were determined to be 275 ± 47 kJ mol−1 for the anhydrous melt and 209 ± 58 kJ mol−1 for the hydrous melt. The high CO2 activation energy in the leucititic melt indicates that the diffusion might be partly attributed to the carbonate species. At high magmatic temperatures above 1200 ∘C, CO2 diffusivity in the leucititic melt is only slightly lower than CO2 diffusion in rhyolitic and basaltic melts, suggesting that CO2 diffusion in natural melts is relatively independent from the bulk melt composition at such temperatures. CO2 diffuses slower than other volatile components such as halogens and H2O in depolymerized silicate melts. Thus, a fractionation of volatiles can occur during magma ascent and degassing. The experimental data on CO2 diffusion can be used for modelling the degassing mechanisms of ultrapotassic mafic melts.

Quantification of preferential and mutual mass transfer of gases-light oil systems at high pressures and elevated temperatures by dynamic volume analysis

• Dynamic liquid volume due to gas dissolution and light-component extraction is measured and recorded continuously. • Gas fractions at the beginning and end of each test is respectively measured with GC. • Light-component extraction from oil phase to gas phase results in a shrinkage of the oil phase with pressure. • Both individual diffusion coefficients for each gas component of a gas mixture in the oil phase and oil components extracted from oil phase to gas phase are increased with pressure. • By isolating natural convection from the molecular diffusion, larger diffusivities are determined. In this study, a robust and pragmatic technique has been developed for the first time to quantify preferential and mutual mass transfer of gases-light oil systems at high pressures and elevated temperatures by performing dynamic volume analysis. Experimentally, diffusion tests have been conducted for gases-light oil systems at high pressures and a constant reservoir temperature with a PVT setup. During experiments, the dynamic liquid volume due to gas dissolution and light-component extraction has been measured and recorded continuously, while gas fractions at the beginning and end of each test have been measured with gas chromatography (GC) analysis, respectively. Theoretically, the preferential and mutual diffusion between gas and oil phases can be quantified by minimizing the discrepancies between the measured and calculated swelling factor and gas composition. According to the measured swelling factors, oil swelling effect slows down during the late stage of a diffusion experiment, indicating that CO 2 dissolution is transited from the natural convection-dominated period to the diffusion-dominated period. Compared to the swelling effect at a higher pressure, the effect of light-component extraction on the determined diffusion coefficients of gas components becomes weaker. In addition, both individual diffusion coefficients for each gas component of a gas mixture in an oil phase and oil component extracted from the oil phase to the gas phase are increased with pressure. The diffusion-convection model allows us to isolate the natural convection from the molecular diffusion, leading to larger diffusivities compared with the ones determined from the conventional method.

Salt and ion transport in a series of crosslinked AMPS/PEGDA hydrogel membranes

Salt permeability and ionic conductivity are critical properties for membranes in water purification and energy applications. Both properties depend on individual ion sorption and diffusion coefficients, which are significantly influenced by polymer chemical and physical parameters such as fixed charge concentration and membrane water content. However, systematic studies connecting polymer structure to ion transport properties are still lacking. In this study, a series of uncharged and charged membranes were synthesized using poly(ethylene glycol) diacrylate (PEGDA) as a cross-linker and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as a charged monomer. Membrane fixed charge concentration and water uptake were systematically varied by adjusting AMPS content in the pre-polymerization mixture. Salt sorption and permeability coefficients and ionic conductivity of these membranes were measured as a function of NaCl solution concentration (0.01–1 M). Combining the solution-diffusion model and Nernst-Planck equation, individual ion diffusion coefficients were calculated. Experimental Na+ diffusion coefficients for all materials were well described by the Mackie and Meares tortuosity model, highlighting the strong influence of water content on ion diffusivity in both uncharged and charged polymers. Model predictions for Cl− diffusion coefficients agree reasonably well with experimental values, with some deviations occurring in more highly charged membranes. This discrepancy might result from interactions not captured by the Mackie and Meares model (e.g., fixed charge-ion interactions).

A model of interdiffusion occurring during the formation of thin metal films on single-crystal silicon under conditions of limited solubility of the components

Thin metal films are used in semiconductor and microelectronic devices to form ohmic and non-ohmic contacts to singlecrystal silicon. A common feature of the used Ме–Si systems is the low mutual solubility of elements and the polycrystalline nature of metal films. Solid-phase interactions during the deposition of metals on single-crystal silicon and the subsequent vacuum annealing results in the redistribution of the elements near the Me/Si interface. An important task facing the material science of solid-state electronics is to develop a mechanism of solid-phase interaction of metal thin films and single-crystal silicon. The aim of our study – was to develop a quantitative model of interdiffusion in the Ме–Si system under conditions of limited solubility of the components. The article suggests a mechanism of formation of Me–Si systems based on the diffusion and segregation of silicon near the intergrain boundaries of the metal and the limited formation of complexes during the diffusion-induced penetration of metal into silicon. The article suggests a model of reactive interdiffusion in thin metal film – single-crystal silicon systems under conditions of limited solubility of the components. Mathematical modelling was used to study the interaction of magnetron-sputtered metals Ti, W, and Nb with single-crystal silicon during isothermal vacuum annealing. The numerical analysis of experimental distributions of concentrations of Me and Si obtained by Rutherford backscattering spectroscopy allowed us to determine their individual diffusion coefficients in Me-Si systems. The model can be used for empirical studies of the redistribution of the elements of two-layer systems with limited solubility, as well as to forecast the technological conditions for the production of electronic devices.

Quantification of gas exsolution and preferential diffusion for alkane solvent(s)–CO2–heavy oil systems under nonequilibrium conditions

The in-situ formation of foamy oil has been found to be a crucial mechanism accounting for the better-than-expected production performance in heavy oil reservoirs under solution gas drive. Not only have the physical laws dominating gas exsolution in foamy oil not yet been well understood, but also the different contributions of each component in a gas mixture to the generation of foamy oil associated with an extremely complicated dynamic process has not been quantified. In this study, a novel and pragmatic technique has been proposed and validated to quantify the gas exsolution and preferential diffusion for alkane solvent(s)–CO2–heavy oil systems under nonequilibrium conditions by taking gas bubble size distribution and preferential mass transfer of each gas component into account. Experimentally, constant-composition expansion (CCE) tests with various constant-pressure decline rates are utilized to describe gas exsolution behaviour of alkane solvent(s)–CO2–heavy oil systems under nonequilibrium conditions, during which not only pressure and volume are simultaneously monitored and measured, but also gas samples were respectively collected at the beginning and end of experiments to perform compositional analysis. Theoretically, a mathematical model has been formulated to quantify gas exsolution and preferential mass transfer between each gas component and the liquid phase in alkane solvent(s)–CO2–heavy oil systems under nonequilibrium conditions. More specifically, quasi-equilibrium boundary conditions, real gas equation, and Rayleigh distribution function are combined with the classical equation of motion, continuity equation, and mass transfer equation to form a novel equation matrix for quantifying gas bubble growth in foamy oil. Considering gas bubble size distribution and preferential diffusion of each component in a gas mixture, the total number of gas bubbles and individual diffusion coefficient of each gas component are determined by minimizing the discrepancy between the measured and calculated volume of alkane solvent(s)–CO2–heavy oil systems. More importantly, the dynamic composition of the gas phase and the amounts of both entrained gas and evolved gas can also be obtained simultaneously during the gas exsolution processes. Excellent agreements between the experimentally measured parameters (i.e., volume of foamy oil, composition of evolved gas, and volume of free gas) and the calculated ones have been respectively achieved. Compared with the individual diffusion coefficient for each component in a gas mixture determined under the traditional equilibrium conditions, a relatively large value has been found during mass transfer processes in a supersaturated oleic phase. Moreover, pseudo-bubblepoint pressure and gas exsolution rate are found to be two main mechanisms dominating the volume-growth rate of the evolved gas.

Measurement of Interdiffusion and Tracer Diffusion Coefficients in FCC Co-Cr-Fe-Ni Multi-Principal Element Alloy

Average effective interdiffusion coefficients of individual components and tracer diffusion coefficient of Ni were experimentally determined in FCC CoCrFeNi high entropy alloys. Average effective interdiffusion coefficients of individual elements in CoCrFeNi alloys were determined using the Dayananda-Sohn approach. Cr had the highest while Ni had the lowest magnitude of the average effective interdiffusion coefficient in the CoCrFeNi alloy. The tracer diffusion coefficient of Ni was determined without the application of radiotracers using the novel analytical method proposed by Belova et al. based on linear response theory coupled with the Boltzmann-Matano approach and Gaussian distribution function. Both average effective interdiffusion coefficients and tracer diffusion coefficients in CoCrFeNi were compared with the relevant high entropy alloys with varying entropy of mixing. The diffusion of individual elements in Al-containing high entropy alloys (e.g., Al-Co-Cr-Fe-Ni and Al-Co-Cr-Fe-Ni-Mn), with higher entropy of mixing, was higher than that in CoCrFeNi alloy, with relatively lower entropy of mixing. Therefore, diffusion cannot a priori consider to be sluggish in alloys with higher configurational entropy. Moreover, potential energy fluctuations determined in quinary and senary Al-containing high entropy alloys were higher than that in quaternary CoCrFeNi alloy. This also suggests that the diffusivity of a component may not be always lower in the alloys which possess higher fluctuations in potential energy or configurational entropy of mixing.

Effects of binders characteristics and concrete dosing parameters on the chloride diffusion coefficient

Rebar corrosion in reinforced concrete is one of the most serious manifestations that affect structures, resulting in considerable technical, financial, and social consequences. The corrosive process can be accelerated by carbonation or the action of chlorides, the latter being the phenomenon of greatest concern, since a large part of the world population lives close to a coast. This study analyzed how the characteristics of the cement and the dosing parameters of the concrete influence the diffusion of chlorides in both an isolated and in a combined manner. For this, several concretes were dosed with different water/cement and water/binder ratios, types of cement, mortar content, and mineral additions, each of which had their individual diffusion coefficients obtained from the chloride migration test. It was observed that the water/cement ratio is not the primary parameter for controlling the diffusion of chlorides in concrete. The aluminate content, the fineness of the cement used, and the water/binder ratio, more significantly affect chloride diffusion.

Application of Potentiometric Ion-Breakthrough to Assess Individual Diffusion Coefficients of Ions in Ion-Selective Membranes

Ion-selective membranes (ISMs) are at the core of ion-selective electrode development. Fundamentally, two groups of parameters determine the response of ISMs: selectivity coefficients and diffusion coefficients of mobile species in the membrane. It is possible to assess both by performing a single potentiometric ion-breakthrough experiment. Basically, the ISM is placed between two contacting electrolyte solutions that do not contain the ion that the ISM is selective for (primary ion). After primary ion is added the potential trace carries valuable information about the thermodynamics and the kinetics of the membrane. So far, extracting parameters from the experimental results was possible only after unrealistic simplifications (e.g. assuming all of the diffusion are the same). The state-of-the-art simulation technique the Nernst-Planck-Poisson finite element method is utilized to give insight on how the different physico-chemical processes generate the measured potential. Numerical simulations are used to train a feedforward neural network, in order to learn the connection between the physico-chemical parameters (e.g., thickness, diffusion coefficients, selectivity coefficients, coextraction etc.) and the shape of ion-breakthrough potential trace. By using the trained neural network it was possible to quickly obtain for the first time the diffusion coefficient of all of the mobile species in the ISM.

Influence of water content on alkali metal chloride transport in cross-linked Poly(ethylene glycol) diacrylate.2. Ion diffusion

In this study, the influence of polymer water content on ion diffusion coefficients of alkali metal chlorides (LiCl, NaCl, and KCl) in cross-linked poly(ethylene glycol) diacrylate (XLPEGDA) hydrogels was investigated. This research is part of a broader effort to understand the fundamentals of water and ion transport in hydrated polymers. Salt diffusion coefficients were calculated from salt permeability and sorption measurements. XLPEGDA hydrogels were synthesized with three different water contents (50, 67, and 93 g water/g dry polymer). The diffusion coefficients of alkali metal chlorides in XLPEGDA polymers increased as water content increased. The Mackie and Meares model, which accounts for polymer chain obstruction (i.e., tortuosity) effects on salt diffusion in hydrated polymers, was used to interpret salt diffusion coefficients. The general trend of the experimentally determined salt diffusion coefficients in these polymers is consistent with the model. Individual ion diffusion coefficients in the samples were obtained by combining salt permeability/sorption data with ionic conductivity results. The chloride ion diffusion coefficients were similar for all salts. The relative order of alkali metal ion diffusion coefficients in these polymers was different from that in aqueous solution (i.e., DK+s>DNa+s>DLi+s). Moreover, this order changes as polymer water content varies, suggesting that alkali metal chloride diffusion behavior in XLPEGDA polymers is influenced by both ion hydration and polymer-ion specific interactions.

Formula omitted]-Nash mean-field games for general linear-quadratic systems with applications

This paper is concerned with general mean-field (MF) linear-quadratic (LQ) games of stochastic large-population system, where the individual diffusion coefficient can depend on both the state and the control of the agent. Moreover, the control weight in the cost functional could be indefinite. The asymptotic suboptimality property (namely, ϵ-Nash equilibrium) of the decentralized strategies for the LQ games is derived through the consistency condition. The impact of the population’s collective behaviors and the consistency of the mean field estimation are illustrated by the numerical results. A pricing problem is also studied, for which the decentralized suboptimal price is obtained.

Systematic parameter acquisition method for electrochemical model of 4.35 V LiCoO2 batteries

Electrochemical model plays an important role in studying the relationship between the corresponding parameters and battery performance. To improve the accuracy and persuasion of the electrochemical model, a systematic method for key parameters acquisition in 4.35 V LiCoO2 batteries with wound type cell design is presented in this paper. The design specification, lithium ion concentrations, kinetic parameters are measured using different experimental and computational method. In this work, the volume fractions, porosity, states of charge of individual electrodes, diffusion coefficient and membrane impedance Rsf of LiCoO2/graphite pouch cells were estimated. It is found that the diffusion coefficients during discharge processes are larger than the values in the charge processes by Galvanostatic intermittent titration technique (GITT), while the diffusion coefficient calculated by electrochemical impedance spectroscopy (EIS) showed two orders of magnitude smaller as compared with GITT. Based on the experimental and computational results obtained herein this work, the pseudo-two-dimensional (P2D) electrochemical model can predict the electrochemical characteristics with high accuracy.

Modeling of the reaction interdiffusion in the polycrystalline systems with limited component solubility

that may be accompanied by the processes of mutual diffusion and phase formation. Controlled technological process of forming coatings with the given properties entails the necessity of forecasting the evolution of the phase composition. This in turn requires the development of algorithms and quantitative models of the processes. Reactive mutual diffusion in polycrystalline metal (oxide film systems with limited component solubility) has not been simulated before. The simulation allows selecting the annealing conditions (time and temperature) necessary for the inclusion and uniform distribution of metal in the oxide lattice. A quantitative model of the interaction in a multi-layer system metal — polycrystalline oxide of the other metal under conditions of limited solubility is developed. The model is based on the concepts of mutual diffusion of the components and the bulk reactions of the formation of complex oxides. The developed model was applied to the analysis of the process of modifying thin films of titanium oxide with transition metals. The model allowed us to perform a numerical analysis of the experimental concentrations of the component distributions in polycrystalline Co - Ti02 and Fe - Ti02 thin-film systems. The individual diffusion coefficients of the studied metals and titanium under conditions of vacuum annealing were determined. The model provides a good description of the basic systematic features of the process: the appearance of titanium in the metal film and deep penetration of Fe and Co into the film of titanium oxide. It also explains the fact that complex oxides are formed not by layer-by-layer growth at the metal-oxide interface, but throughout the entire thickness of Ti02 film. The results of analysis of the processes of interracial interaction in layered systems accompanied by the reaction mutual diffusion can be used to predict the evolution of the phase composition, as well as to control the technological processes of obtaining materials with the desired properties.

Quantification of gas exsolution of alkane solvents-CO2 mixture in heavy oil with consideration of individual interfacial resistance under nonequilibrium conditions

A novel and pragmatic technique has been developed and validated to quantify gas exsolution of alkane solvent(s)–CO2–heavy oil systems with consideration of interface mass transfer for each gas component under nonequilibrium conditions. Experimentally, constant composition expansion (CCE) tests of three alkane solvent(s)–CO2–heavy oil systems are conducted with a visualized PVT cell under equilibrium and nonequilibrium conditions. The liquid height and pressure of the system are continuously monitored and recorded during experiments to measure, respectively, the bubblepoint pressure, pseudo-bubblepoint pressure, and the entrained gas volume. With the assumption of instantaneous nucleation, a mathematical model which integrates Peng-Robinson equation of state (PR EOS), Fick's second law, and nonequilibrium boundary condition has been developed to quantify not only the amount of the evolved gas and entrained gas, but also the dynamic composition of gas phase as a function of time. Once the deviations between the measured gas volumes and the calculated ones have been minimized, the mass transfer Biot number, individual diffusion coefficient, and interface mass transfer coefficient of each gas component as well as the gas bubble number are determined. Increases in experimental temperature and pressure are found to impose opposite effects on diffusion coefficient during gas exsolution processes. The diffusion of each gas component is found to be faster when the temperature becomes higher or the initial pressure becomes lower. Either CO2 or C3H8 diffuses faster than CH4 in the liquid phase under the same condition. In addition, the interface mass transfer coefficients, with an order of CO2 > CH4 > C3H8, obtained in this study are much higher than those collected in the literature since the nonequilibrium conditions greatly facilitate gas exsolution. The determined mass transfer Biot numbers in this study are large, indicating that the bulk resistance due to molecular diffusion inside the heavy oil dominates the gas exsolution process compared to the interfacial resistance.

Diffusion equation modeling for sound energy flow analysis in multi domain structures.

This study investigates reliable models and methods to be applied in sound field analysis of multi-domain structures. The case structures are two monuments, namely, Süleymaniye Mosque and Hagia Sophia in İstanbul. These are both multi-volume spaces with many smaller sub-volumes coupled to each other by coupling apertures in form of arches. A key concern of the study is to examine energy flow decays and understand the mechanism of multi-slope sound energy decays. The methodology involves diffusion equation model (DEM) application in a finite-element scheme for sound energy flow analysis. Energy flow decays, energy flow dips, and spatial flow vectors are examined for single versus multi-domain DEM solutions. It is concluded that specification of different domains with individual diffusion coefficients is a critical setting such that, if not assigned correctly, may mislead the results. The energy flow vector analysis has enabled us to comprehend the architectural features in relation to such energy flow decay dip occurrence. The computational efficiency of DEM is also discussed. The DEM application in this study has proved to be a powerful and practical method in room acoustics applications, specifically for multi-rate decay investigations.

Modeling of the static batch desorption and dynamic column elution of geniposidic acid from a porous anion-exchanger

For several decades, plenty of iridoid glycosides including geniposide (GS) and geniposidic acid (GSA) in the gardenia yellow pigment extraction waste water was not recovered effectively. This study is aimed to supply an efficient GSA recycling route. In this study, a model incorporating a superficial desorption rate constant was applied to the batch GSA desorption process, i.e., recycling, for verification. Then, the model was further developed to research the feasibility in dynamic column elutions simulation through porous uniform media. The simulation approach was done by coupling velocity field and mass transfer equations using COMSOL Multiphysics™ Finite element method, with appropriate mesh refinement was employed to solve the equation system. The HCl solutions ranging from 0.03 mol/L to 0.06 mol/L were used to desorb/elute the GSA from a presaturated polymeric porous anionic resin D08. Good results were accomplished in terms of ion exchange desorption rate and GSA recovery. The pore diffusion model (PDM) considering counter ion was established to describe the desorption/elution kinetics in the batch/column experiment. By the least square fitting method, the superficial desorption rate constant Kd of GSA/HCl reaction on the ion-exchange sites of porous resin was fitted to 0.116 L/(mol s). Subsequently, this value was sequentially applied in the simulation of the dynamic elution process. The individual pore diffusion coefficients for GSA and Cl− were estimated to be 5.07 × 10−10 and 1.77 × 10−9 m2/s, respectively. In order to validate the simulation feasibility of this pore diffusion model to a dynamic column elution process, the effects of HCl concentration, flow rate and column's height/diameter ratio on the column performance were investigated systematically. The results from this work should serve as motivation for further experimental and theoretical study in the scaling-up of GSA purification process. Finally, repeated adsorption–elution column cycles were simulated by the PDM model well.

Simultaneous and time resolved investigation of diffusion processes of individual model fuel components in acrylonitrile-butadiene-rubber in the light of swelling phenomena

This work introduces a method allowing a simultaneous and time resolved tracing of diffusion processes of individual components of model fuel mixtures in elastomers using gas chromatography/mass spectrometry (GC/MS). Uptakes of dodecane and m-xylene, representing typical fuel components, were monitored in acrylonitrile-butadiene-rubber (NBR) specimens, which were stored in different mixtures of these two compounds. Calculations of individual diffusion coefficients and saturation concentrations of each substance show rising uptakes and diffusion rates of both constituents with increasing m-xylene content of the mixture. Additionally, sorption curves of dodecane were recorded for elastomers, which were pre-swollen in m-xylene or decalin. At the same time, the extraction of the pre-swelling agents was traced. Diffusion coefficients of dodecane were significantly higher compared to those found for the neat material.By immersing elastomers in binary mixtures containing different model fuel constituents, a relation between concentrations in the bulk fluid, individual swelling potentials of the mixtures' components and the attained equilibrium concentrations in the elastomer could be determined. In general, swelling potentials of mixtures are governed by the constituent with the highest individual swelling potential. Results from experiments involving model substances were interpreted in terms of the influence of a real fuels' composition on its swelling behavior towards elastomers contributing to a better understanding of diffusion processes.

A novel time lag method for the analysis of mixed gas diffusion in polymeric membranes by on-line mass spectrometry: Method development and validation

A novel method to determine the individual diffusion coefficients of gases in a mixture during their permeation through polymeric membranes is described. The method was developed in two independent laboratories, using rubbery Pebax® and glassy Hyflon® AD60X membrane samples as standards, and validated using the Tröger's base containing Polymer of Intrinsic Microporosity, PIM-EA-TB. Monitoring of the permeate composition in real time by a quadrupole mass spectrometer allowed the analysis of the permeation transient for gas mixtures. Two operation modes, either with a vacuum in the permeate and a direct connection to the mass spectrometer via a heated restriction, or using a sweeping gas and a heated capillary sample inlet, give excellent agreement with the traditional time lag method for single gases. A complete overview of the method development, identification of the critical parameters, instruments calibration, data elaboration and estimation of the experimental accuracy are provided. Validation with PIM-EA-TB, shows that the method can also successfully detect anomalous phenomena, related to pressure and concentration dependency of the transport properties, physical aging or penetrant-induced dilation. Rapid online analysis of the permeate composition makes the method also very suitable for routine mixed gas permeability measurements.

Cobalt Modification of Thin Rutile Films Magnetron-Sputtered in Vacuum

Using X-ray phase analysis, atomic force microscopy, and secondary ion mass-spectrometry, the phase formation and component distribution in a Co–TiO2 film system have been investigated during magnetron sputtering of the metal on the oxide and subsequent vacuum annealing. It has been found that cobalt diffuses deep into titanium oxide to form complex oxides CoTi2O5 and CoTiO3. A mechanism behind their formation at grain boundaries throughout the thickness of the TiO2 film is suggested. It assumes the reactive diffusion of cobalt along grain boundaries in the oxide. A quantitative model of reactive interdiffusion in a bilayer polycrystalline metal–oxide film system with limited solubility of components has been developed. The individual diffusion coefficients of cobalt and titanium have been determined in the temperature interval 923–1073 K.

Sorption measurements of autoclaved aerated concretes diffusion coefficient

This study presents the results of sorption measurements and analyzes their applicability in the determination of the moisture diffusion coefficient in the porous media in which these processes occur. The test involved three classes of autoclaved aerated concrete density: 500, 600 and 700. The sorption processes under examination covered practically the whole range of hygroscopic humidity from RH = 0% up to RH = 98%. The idea of the experiment was to place dry samples of the tested concretes to 98% relative humidity stimulated by the saturated water solution of K2SO4. The tests were performed until weight stabilization of all samples, which took about 10 months. On the basis of the results obtained, individual diffusion coefficients were determined using two different calculation procedures: the square root of time method and the logarithmic method. The first method applies to the initial stage of the process, while the other is used at its advanced stage. Both measurement methods were assessed in terms of their applicability and compatibility.