posted on 2012-05-31, 00:00authored byGuangyin Jing, Jun Ma
Curved cracks widely exist in nanoparticle (NP) deposition
produced
by drying colloidal suspension. Circular cracks, for example, initiate
and propagate along a circular trajectory. One feasible theoretical
explanation of a circular crack is the Xia-Hutchinson model, in which
a preexisting track (flaw loop) in the film is necessary for initiating
and propagating the crack on the circular path. Here, we report the
first experimental evidence of dried deposition to support this model.
Our results indicate that cracks along the circular trajectory can
surprisingly “pass” across a 180 μm air gap. Moreover,
two arc-path cracks originate in different areas and propagate to
meet, forming a circular trajectory. These unexpected crack initiation
and propagation indicate that the crack propagates alone the “preformed”
track, experimentally confirming the hypothesis proposed by the Xia–Hutchinson
model. The transition of the circular crack to a radial one indicates
that the deposition microstructure is the dominant factor for the
crack formation.