Diffusion and vaporization

Effect of molecular diffusion and vapor-phase chemical reactions Liquid metal vapors consist of molecules and gaseous atoms. Working with alkali metals, Ewing et al. (1967) found that the molecules are principally dimers and tetramers. The... 

Mercury diffusion and vapor-jet pumps are less sensitive to air ingress than oil diffusion pumps. The oxidation of the hot mercury caused by the air ingress is negligible in regard to the operating characteristics of the pump when compared with the mercury loss in the forepump line. 

Operating errors with diffusion and vapor-jet pumps... 

Vapor transport differs from surface diffusional transport, where the flux is always in the surface plane. For both surface diffusion and vapor transport, the diffusion potential at the surface is proportional to the local value of 7sk if the surface free energy is isotropic. For surface diffusion, the interface normal velocity is related to a derivative (i.e., the divergence of the flux). Also, the total volume is conserved during surface diffusion. For vapor transport, the interface normal velocity is directly proportional to the vapor flux, and the total number of atoms is not necessarily conserved. 

A fixed amount of condensed phase enclosed by an interface will undergo essentially the same process, except that the time scales may differ greatly. For solid phases, the interfaces will reduce gradients in curvature by diffusional processes such as interface diffusion, crystal diffusion, and vapor transport. At similar time scales (in the case of crystal diffusion) interfaces will move because atoms will experience differences in diffusion potential across an interface arising from differences in the curvature according to Eq. 3.76. 

Review of diffusion and vaporization of Group 4 and 5 transition metal carbides... 

Matter transport occurs by several mechanisms or paths. The four main mechanisms for crystalline ceramics are shown in Figure 1 for two particles. The easiest mechanisms are surface diffusion and vapor transport (evaporation/condensation). Both... 

The present review will cover the phase equilibria of these ceramic nuclear fuels at high temperatures, and a summary will be given on their nonstoichiometric region, defect structure and thermodynamic data. In addition, diffusion and vaporization processes will be taken as representative phenomena eharacteristic of these materials at high temperatures, and these phenomena also will be reviewed in their relation to nonstoichiometry. 

Several researches have been carried out to understand the mechanism of moisture movement in clay during drying. Newitt et al. [12] and Wakabayashi [13] investigated the moisture movanent in clay by liquid diffusion and vapor diffusion, which affect the drying characteristics particularly the falling rate. They concluded that the liquid diffusion dominates the movement until about 20%-dry basis in moisture content for stoneware clay and 30% for the mixture of 80% Kibushi clay and 20% feldspar. Wakabayashi [14] also evaluated the effective moisture diffusion coefficient of some sorts of clay such as Kibushi, Gairome, stoneware, feldspar, and their mixtures. The effective diffusion coefficient is available for the brief description of the moisture movement behavior. The effective diffusion coefficient D can be defined by... 

For a given powder system, if it is assumed that grain boundary diffusion and vapor transport (evaporation/condensation) are the dominant mass transport mechanisms, the rates of sintering by these two mechanisms vary with the scale of the system with the following relations ... 

Chandrasekaran SK, King CJ. Multicomponent diffusion and vapor-liquid equilibria of dilute organic components in aqueous sugar solutions. AIChE J. 18(3) 513-520, 1972b. 

The relative contributions of diffusion and vaporization have not been critically examined for volatile emissions from rubber, although the... 

---