Segregation rates

Watt G. R., Burns I. M., and Graham G. A. (1996) Chemical characteristics of migmatites accessory phase distribution and evidence for fast melt segregation rates. Contrib. Mineral. Petrol. 125, 100-111. 

We make clear the following facts in this study. The K/Cu-Zn-Fe oxides catalyst has a spinel type structure. The K/Cu-Zn-Fe oxides catalyst is deactivated by the segregation of catalyst components to FeCOj, ZnO, and Cu during the reaction. The segregation is prevented by the addition of Cr component to the catalyst. The long life of K/Cu-Zn-Fe-Cr oxides catalyst can be explained by its slow segregation rate. It is considered that the Cr component stabilizes thermally the spinel type structure of the catalyst. 

Model Ni/MnOx catalysts have been prepared by deposition of 150 of Ni onto an oxidized Mn disk. Subsequent reduction at 500 K in ul-trahigh vacuum results in rapid segregation of MnO onto the Ni surface. The segregation rate is ouch faster than that of Ti under identical conditions. HREELS studies reveal new C-0 stretching bands at lower frequencies, comparable to what have been observed on Rh promoted with Mn. We assign these bands to be due to CO chemisorbed on or near MnO sites. 

The segregation rate can be found from the difference of Qp products. The redistribution of volume fractions is then determined by the continuity equation... 

Camberlin Y and Pascault J P (1983) Quantitative DSC evaluation of phase segregation rate in linear segmented polyurethanes and polyurethaneureas, J Polym Sci 21 415-423. 

Golick, L. A. and Daniels K. E. 2009. Mixing and segregation rates in sheared granular materials. Phys. Rev. E 80 042301. 

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