ALD deposited amorphous alumina coatings can slow glass alteration

Abstract

Atomic layer deposited (ALD) amorphous aluminium oxide and titanium oxide coatings have been investigated for use in reducing the rate of silicate glass alteration. Mass spectrometric analysis of leachate from elevated temperature aqueous immersion alteration experiments showed a marked decrease in the concentration of released Na and Si from the glass when the vitrified material was ALD coated as compared to uncoated glass. This decrease is consistent with the proposed protective effect of the ALD coating. Additionally, visual observations indicate formation of significant amounts of amorphous, secondary phase sediment for immersed, uncoated glass. This sediment was not present in the solution of the ALD coated and altered glass samples. However, the ALD coating did delaminate after protracted immersion, a likely limiting factor of the efficacy of ALD coatings. This limitation may be mitigated through a proposed refinement of the ALD coating procedure.