Morphology of silica and borosilicate glass fracture surfaces by atomic force microscopy

Fracture surfaces of Herasil (silica) and Duran (borosilicate) glass rods were examined with an atomic force microscope. Generally the roughness in the fracture surface increases with growing distance from the origin of fracture. The morphology displays a Variety of features. In the smooth fracture mirror near the origin of fracture the surface consists of small hillocks approximate to 25 nm in diameter and less than or equal to 1 nm high. With growing distance these hillocks increase in size and height. In the mist zone bigger outcrops occur with steep flanks. Steps can also be discovered in the fracture surface. Parts of the surface are covered by ripples, which are proposed to result from a local melting of the glass near the crack tip during fracture.