Diffusion of ions and gases

Ushiyama and Goto (U15) studied the diffusion of ions in a Portland cement paste of w/c ratio 0.4 cured at 20 C for 28 days. Pick s second law was shown to be followed when a steady state had been reached. For Li. Na and K , diffusion coefficients of 1.4-3.3 x 10 m s were obtained. That of Cl was somewhat greater, especially if the balancing cation was Ca or Mg. It was shown that CH and MH crystallized at the surface of the specimen, suggesting that CH within the specimen had dissolved. 

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Anderko and Lencka find. Eng. Chem. Res. 37, 2878 (1998)] These authors present an analysis of self-diffusion in multicomponent aqueous electrolyte systems. Their model includes contributions of long-range (Coulombic) and short-range (hard-sphere) interactions. Their mixing rule was based on equations of nonequilibrium thermodynamics. The model accurately predicts self-diffusivities of ions and gases in aqueous solutions from dilute to about 30 mol/kg water. It makes it possible to take single-solute data and extend them to multicomponent mixtures. 

Polymerization Mechanism in Region III. In region III, all the electrons cannot be transported to the anode in a half cycle of the discharge frequency. A possible charge transportation mechanism is an ambipolar diffusion of ion and electron pairs which will cause polymerization. The diffusion of free radicals may also contribute to the polymerization. In our experiment, the contribution of these two mechanisms cannot be distinguished because the ion and electron pairs behave as neutral gases. 

McDaniel, E. W., Mason, E. A. The mobility and diffusion of ions in gases. New York John Wdey and Sons, 1973, 372 pp... 

McDaniel, E.W., Mason, E.A. (1973), The Mobility and Diffusion of Ions in Gases, Wiley, New York. 

The ion transport in strong electric fields would have likely remained a matter of academic curiosity if not for the advent of differential MS paradigm. The impact of field intensity on the mobility and, to a lesser extent, diffusion of ions in gases is as... 

These effects of differential vapor pressures on isotope ratios are important for gases and liquids at near-ambient temperatures. As temperature rises, the differences for volatile materials become less and less. However, diffusion processes are also important, and these increase in importance as temperature rises, particularly in rocks and similar natural materials. Minerals can exchange oxygen with the atmosphere, or rocks can affect each other by diffusion of ions from one type into another and vice versa. Such changes can be used to interpret the temperatures to which rocks have been subjected during or after their formation. 

The permeability of concrete and the rates at which ions and gases diffuse in it are of major importance for durability. We shall consider only the behaviour of cement paste. 

Warneck has carried out an extensive series of experiments in which he used a pulsed nitrogen-spark light source to determine drift velocities, diffusion coefficients, and kinetic temperatures as well as reaction rates of ions in gases. These have been the only photoionization experiments in which a pulse technique has been effectively used in the study of ion-molecule reactions. The reactant ions were formed by repetitive light pulses of about 0.5-//sec average duration, which (in all cases except hydrogen) was sufficiently short to justify the approximation of instanta-... 

Mason, E. A. McDaniel, E. W. Measurement of drift velocities and longitudinal diffusion coefficients. In Transport Properties of Ions in Gases, John Wiley Sons, New York, 1988, Chapter 2, pp. 31-102. 

Viehland L A and Robson R E 1989 Mean energies of ion swarms drifting and diffusing through neutral gases Int. J. Mass Spectrom. Ion Processes 90 167-86... 

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