Materials Science

Dissecting a Breakup

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Science  11 Jun 2004:
Vol. 304, Issue 5677, pp. 1567-1569
DOI: 10.1126/science.304.5677.1567d

When a material breaks into more than one piece, the cleavage occurs through some combination of brittle and ductile failure. During brittle failure, bonds are ruptured and there is little overall stretching of the material. During ductile failure, atoms or molecules slide past each other and the material deforms plastically before finally breaking. Glass is typically thought to break only through brittle failure, although it is known that plastic deformation will occur when glass is indented or scratched. Recent observations also suggested that cavities formed during glass fracture, implying that brittle materials also fracture via plastic flow instead of via bond rupture.

Guin and Wiederhorn used atomic force microscopy to study the topology of slowly fractured silica and soda-lime-silicate glasses. Mapping the high-contrast points from one of the fracture surfaces revealed that they mirror those on the opposing surface. Line scans of the two surfaces revealed that the vertical error between the profiles, i.e., the extent to which they don't overlap, was less than 0.3 nm, and the horizontal error was less than 5 nm. Within the limits of the resolution of the atomic force microscope, the authors conclude that glass fracture only occurs via the local rupture of atomic bonds. — MSL

Appl. Phys. Lett. 92, 215502 (2004)

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