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Differences in surface failure modes of soda lime silica glass under normal indentation versus tangential shear: A comparative study on Na + /K + ‐ion exchange effects
Author(s) -
Luo Jiawei,
Grisales William,
Rabii Matthew,
Pantano Carlo G.,
Kim Seong H.
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16019
Subject(s) - soda lime , indentation , materials science , ion , composite material , silicate , relative humidity , humidity , mineralogy , calcium silicate , chemistry , physics , organic chemistry , thermodynamics
The effects of exchanging Na + with K + on the mechanical and mechanochemical properties of a soda lime silica ( SLS ) glass were investigated. It is known that replacing smaller modifier ions with bigger ions in the silicate glass network, at temperatures below the glass transition (T g ), produces a compressive stress in the subsurface region that enhances resistance to mechanical damages. This study found that when Na + ions in SLS are exchanged with K + ions at 400°C, the hardness, indentation fracture toughness, and crack initiation load of the surface are increased, which is consistent with the chemical strengthening effect. However, the resistance to mechanochemical wear in a near‐saturation humidity condition (relative humidity RH = 90%) is deteriorated. When K + ions are exchanged back with Na + ions at 350°C, the wear resistance in high humidity conditions is recovered. These results indicate that the improvement of mechanical properties under indentation normal to the surface is irrelevant with the resistance to mechanochemical wear under tangential shear at the surface. Based on the analysis of the surface chemical composition, silicate network structure, and hydrogen‐bonding interactions of hydrous species in the subsurface region, it is proposed that the leachable Na + associated with non‐bridging oxygen and subsurface hydrous species in the silicate network play more important roles in the mechanochemical wear of SLS at high RH .