Modifying glass surfaces via internal diffusion

M.M. Smedskjaer, Y.Z. Yue, J. Deubener, H.P. Gunnlaugsson, Steen Mørup

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The surface chemistry and structure of iron-bearing silicate glasses have been modified by means of heat-treatment around the glass transition temperature under different gaseous media at ambient pressure. When the glasses are heat-treated in atmospheric air, oxidation of Fe2+ to Fe3+ occurs, which leads to outward diffusion (OD) of divalent cations (primarily Mg2+), i.e., diffusion from the interior of the glass to the surface, and thereby, to formation of an oxide surface nano-layer. in contrast, when the glasses are heat-treated in H-2/N-2 gas containing 10 vol.% H-2, reduction of Fe3+ to Fe2+ occurs due to both the permeation and reducing ability of H-2. In this case, CID of divalent ions also occurs, and hence, an oxide surface layer forms. However, such outward diffusion differs from that induced by the iron oxidation in terms of physical origin. The former is due to incorporation of the N3- ions in the network and their strong attraction to the modifying ions, whereas the latter is due to the requirement of the charge neutrality. The role of N3- in driving OD is verified by the composition profile of the surface layer of the glass treated in pure N-2 gas. The OD exerts pronounced impacts on some properties such as hardness, chemical durability, and surface wettability.
Original languageEnglish
JournalJournal of Non-Crystalline Solids
Volume356
Issue number6-8
Pages (from-to)290-298
ISSN0022-3093
DOIs
Publication statusPublished - 2010

Keywords

  • Diffusion and transport
  • Surfaces and interfaces

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