Morphogenesis of Self-Assembled Nanocrystalline Materials of Barium Carbonate and Silica
Juan Manuel García-Ruiz,1
Emilio Melero-García,1
Stephen T. Hyde2
The precipitation of barium or strontium carbonates in alkaline
silica-rich environments leads to crystalline aggregates that
have been named silica/carbonate biomorphs because their morphology
resembles that of primitive organisms. These aggregates are
self-assembled materials of purely inorganic origin, with an
amorphous phase of silica intimately intertwined with a carbonate
nanocrystalline phase. We propose a mechanism that explains
all the morphologies described for biomorphs. Chemically coupled
coprecipitation of carbonate and silica leads to fibrillation
of the growing front and to laminar structures that experience
curling at their growing rim. These curls propagate in a surflike
way along the rim of the laminae. We show that all observed
morphologies with smoothly varying positive or negative Gaussian
curvatures can be explained by the combined growth of counterpropagating
curls and growing laminae.
2 Department of Applied Mathematics, Research School of Physical Sciences, Australian National University, Canberra, Australian Capital Territory 0200, Australia.
