S. Friej et al., AN AFM INVESTIGATION OF THE MECHANISM OF SECONDARY NUCLEATION INDUCEDBY CONTACT, Applied physics A: Materials science & processing, 66, 1998, pp. 507-511
Although secondary nucleation is the main source of new crystal nuclei
in an industrial crystallizer, the precise source of contact nuclei h
as not yet been determined. To address the various theories presented
in the literature, we have adopted the dual approach of using microsco
py to characterize, at their earliest stages of growth, the secondary
nuclei that are produced by contact and also the surface topography of
the primary crystals before and after contact. AFM studies of a range
of crystals, including isomorphous alums, combined with scanning and
transmission electron microscopy experiments indicate that, at least f
or the case of very gentle contact, transfer of crystallographic infor
mation can occur through an ordered solute layer in a supersaturated s
olution without the need for the transfer of solid materials from the
primary crystal by microattrition. Knowledge about this mechanism has
the potential to improve the quality of product from industrial crysta
llizers, through control of crystal morphology and size distribution.