Diffusion couples of elemental iron and degassed sodium disilicide glass rod were prepared under neutral to reducing conditions at several temperatures and at varying times. The diffusion profiles were analyzed by using electron microprobe techniques. Diffusion coefficient calculations and activation-energy determinations indicated that a change in mechanism was occurring between 1000 and 1050° C. An indication is given by the magnetic-susceptibility measurements that atomic iron is the diffusing species at 900°C and that ferrous iron is the diffusing species at 1050° C these observations are supported by the transmission-spectroscopy measurements and by theoretical thermodynamic considerations. A discussion of the possible mathematics of the diffusion processes is given.
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