Diffusion of sodium ions driven by charge compensation as the rate-limiting step of internal redox reactions | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Diffusion of sodium ions driven by charge compensation as the rate-limiting step of internal redox reactions

Type de publication:

Journal Article

Source:

Journal of Non-Crystalline Solids, Volume 365, p.23-26 (2013)

ISBN:

0022-3093

URL:

http://www.sciencedirect.com/science/article/pii/S0022309313000240

Mots-clés:

Géochimie et cosmochimie ; Borosilicate melts; Iron redox reactions; Kinetics; Diffusion in liquids; Charge- compensation, UMR 7154

Résumé:

The kinetics of iron oxidation in sodium borosilicate melts have been determined as a function of time from 710 to 1570 K for four compositions of constant SiO2 content and B2O3 contents ranging from 0 to 22 mol%. The iron redox ratios have been measured by iron K-edge XANES spectroscopy as a function of time at constant temperature. The redox kinetics become slower with increasing B2O3 content. Near the glass transition range, they are controlled by the diffusion of network modifying cations toward the surface of the melt whereas they are limited at superliquidus temperatures by the diffusion of free Na+ ions to charge compensate Fe3 + in tetrahedral coordination, along with the diffusion of oxygen.