It was found that the inward diffusion of network-modifying divalent cations could

occur in iron-containing silicate glasses when they were treated in a reducing

atmosphere near to the glass transition temperature. As a result of the inward

diffusion, a silica-rich nanolayer formed on the glass surface and increased the

hardness and chemical durability. The thickness of the layer could be controlled by

varying the heat-treatment conditions. The mechanism of inward diffusion was

clarified and the diffusion coefficient for the network-modifying divalent cations

was calculated. It was demonstrated that the diffusion of these ions was the ratelimiting

factor in the reduction process.

Inward Cationic Diffusion in Glass. M.M.Smedskjaer, Y.Z.Yue: Journal of Non-

Crystalline Solids, 2009, 355[14-15], 908-12