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Diffusion rare earth solutes

D.T. Hughes and J.R. Harris, Hydrogen diffusion membranes based on some palladium-rare earth solution alloys, Z Phys. Chem. N.F. 777 185 (1979). [Pg.456]

Diffusion of rare earth solutes in other metals... [Pg.871]

A general conclusion of these investigations seems to be that the study of diffusion of rare earth solutes in different metals has been less fruitful than diffusion studies carried out in rare earth matrices. [Pg.871]

Another widely used solution is for an instantaneous planeAine/point source (such as spill of a toxic pollutant, or diffusion of rare Earth elements from a tiny inclusion of monazite or xenotime into a garnet host) to diffuse away in either one dimension, two dimensions, or three dimensions (Figure l-6b). If the source is initially in a plane, which may be defined as x = 0 (note that x = 0 represents a plane in three-dimensional space), then diffusion is one dimensional. If the source is initially a line, which may be defined as x = 0 and y=0, then diffusion is... [Pg.205]

Scandium, thorium and the rare earths The metals are present as nitrates in dilute nitric acid solution. The solvent is 2-methyltetrahydroxyfuran (tetrahydrosylvan) containing 5 per cent (v/v) water and 10 per cent (v/v) nitric acid (d. 1 42). The mixture is spotted upon paper and dried thoroughly in the air. The relative humidity inside the extraction vessel is maintained at 80 per cent by means of a saturated solution of ammonium chloride. After the solvent has diffused about 15 cm down the solvent strip, it is allowed to evaporate, and the strip is placed for about 10 minutes in an atmosphere of ammonia vapour. The paper chromatogram is then sprayed with an alcoholic solution of alizarin and finally with 2m acetic acid. The following results are obtained. [Pg.505]

A peculiar case the YbAlj compound Tibbetts and Egelhoff (1980) have studied Yb thin films deposited on mono-crystal substrates. By XPS and LEED they controlled the inter-diffusion processes. The pure Yb surface layers are in a divalent state (fu-Yb). Above 420 K the interdiffusion becomes substantial and they observed the formation of a mixed-valence state (fij-fu-Yb). Further annealing at 520 K causes a reversion to the divalent state such a phenomenon is also produced by slight ion bombardment. By XPS they showed that the peak concentration of (fis-Yb) appears to coincide with the stoichiometric alloy YbAla. On the other hand they have observed that in a dilute solution of Yb in Al, the rare earth is divalent. [Pg.83]

Metallic solute diffusion in rare earth metals... [Pg.861]

The results of metallic solute diffusion studies in rare earth metals are shown in table 12.3. Also included in this table are values of the ratio K = Da/Da (where D is the solute diffusivity of B in A and Da is the self-diffusion coefficient of A), at the highest temperature at which it could be determined in each phase. Most solute diffusion measurements have been carried out in Ce and Pr. The temperature dependence of the solute diffusivities in these two metals is shown in figs. 12.4 and 12.5. [Pg.862]

Anthony (1970) and Dariel et al. (1%8) have pointed out that one of the characteristic and yet unexplained features of fast diffusion is the small, sometimes barely discernible effect exerted by the phase transformation taking place in the solvent matrix on the solute diffusivities. Such a behavior is in marked contrast to the discontinuous increase of the self and, presumably substitutional, solute diffusivities. Thus, using the effect of the phase transformation as a criterion, it appears that the noble metals, the transition metals (Mn, Fe, Co) and Zn behave as fast diffusers in the rare earth metals. [Pg.864]

Diffusion theory in metals, at its present state of art, is not able to provide a quantitative or even qualitative account for the relative values of the solute diffusivities in rare earth metals. The electrostatic interaction theory, which achieved notable success is accounting for the relative diffusivities of various solutes in the noble metals is not applicable to the polyvalent rare earth solvents (Dariel, 1968). Size effects are probably important in determining relative solute... [Pg.864]

The exceedingly high diffusivity of some metallic solutes in the rare earth elements suggests that a significant fraction of these solutes is able to dissolve as interstitials. This is related to the open structure of the rare earth host atoms... [Pg.865]

A variety of solutes in the rare earth metals present a partly or total interstitial character. These solutes include beside the metalloid classical interstitials also some metallic elements, the so-called fast-diffusers, discussed in section 4. In general the study of electromigration of interstitials offers two advantages as compared to that of substitutional solutes. From the experimental point of view, the relatively high mobilities of the interstitial solutes increases the electrotransport effects often allowing to achieve steady state conditions within... [Pg.867]

Almost no results concerning the electrotransport of substitutional solutes in rare earth metals have been reported. Even for interstitial solutes the results are fragmentary and mostly qualitative. Much is therefore to be yet done in order to achieve a coherent picture of electrotransport phenomena in rare earth metals. The double challenge being offered by the practical applicability of such studies on one hand, and their importance towards furthering the understanding of basic diffusion phenomena in metals on the other, should provide the necessary motivation for additional research in this area. [Pg.869]


See other pages where Diffusion rare earth solutes is mentioned: [Pg.847]    [Pg.863]    [Pg.871]    [Pg.936]    [Pg.72]    [Pg.94]    [Pg.157]    [Pg.132]    [Pg.19]    [Pg.3505]    [Pg.8]    [Pg.170]    [Pg.312]    [Pg.324]    [Pg.25]    [Pg.157]    [Pg.275]    [Pg.69]    [Pg.101]    [Pg.236]    [Pg.84]    [Pg.244]    [Pg.198]    [Pg.847]    [Pg.849]    [Pg.852]    [Pg.853]    [Pg.861]    [Pg.861]    [Pg.862]    [Pg.865]    [Pg.866]    [Pg.866]    [Pg.867]    [Pg.869]   


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