Toughening of Li2O-2SiO(2) glass-ceramics induced by intriguing deformation behavior of lithium disilicate nanocrystal

B Deng and J Luo and JT Harris and CM Smith and ME McKenzie, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 103, 965-972 (2020).

DOI: 10.1111/jace.16794

We report a toughening mechanism of Li2O-2SiO(2) glass-ceramics induced by intriguing anisotropic deformation behavior of lithium disilicate nanocrystal under tensile loadings using molecular dynamics simulations. The nanocrystal undergoes clear brittle cleavage when loaded in the 010 direction, while exhibiting a first-order deformation-induced transition when loaded in the 100 direction. The transition is exclusively facilitated by local Li-O bond breaking, which spreads to the whole sample under continuous loading. This hierarchical deformation mechanism (exclusive Li-O bond breakage prior to any Si-O bond breakage) enables lithium disilicate nanocrystal bearing large amounts of deformation without breaking. We further demonstrate that the toughness of Li2O-2SiO(2) glass-ceramics can be significantly enhanced by deliberate designs of nanocrystal distributions in glass. The direct observation of this intriguing deformation behavior might inspire new ideas to design tougher lithium disilicate glass-ceramics.

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