Is fracture of oxide glasses ductile at the nanometer scale
In plain words
Window glass breaks in a brittle way, but microscope images in 2003 suggested that tiny cavities open ahead of a slowly moving crack, as in a metal. Later work found no such cavities, and whether glass is ductile at the nanometer scale is disputed.
Precise statement
For slow stress-corrosion cracks in silica and aluminosilicate glasses, determine whether crack advance involves a plastic process zone with nanocavities of size about 1e-6 cm ahead of the tip, or atom-by-atom bond rupture with a process zone of a few bond lengths. An answer gives the process-zone size and the fraction of fracture energy dissipated plastically, from in situ imaging or matched fracture-surface analysis and simulations with reliable silica potentials.
What would settle it
In situ, nanometer-resolution imaging of a propagating crack tip in silica, or matched-surface topography with sub-nanometer resolution, consistent with large-scale atomistic simulations.
Status in the literature
Nanocavities reported by atomic force microscopy in 2003 (Celarie et al., Phys. Rev. Lett., https://doi.org/10.1103/PhysRevLett.90.075504) were not found by matched fracture-surface analysis in 2004 (Guin and Wiederhorn, https://doi.org/10.1103/PhysRevLett.92.215502).