%0 Journal Article
%A Pina Martínez, Carlos Manuel
%A Merkel, Casjen
%A Guntram, Jordan
%T On the Bimodal Effects of Silicic Acids on Calcite Growth
%D 2009
%@ 1528-7483, ESSN: 1528-7505
%U https://hdl.handle.net/20.500.14352/52281
%X The effects of silicic acids on calcite growth are a model for the effects of partially polymerized additives on crystal growth. At alkaline pH, silicic acid polymers coexist with small mono- and oligomers. Atomic force microscopy (AFM) showed that large polymers promote two-dimensional nucleation, while mono- and oligomers have a bimodal promoter/inhibitor effect on step propagation. This bimodality can be interpreted as the result of attachment of mono- and oligomers along the steps along with a modification of the kinetics of kink generation and/or propagation. The bimodal step kinematic effect is accompanied by a single morphologic effect: growth islands transform from a rhombus into an ellipse. This effect has been reported for other additives, indicating that many additives generate few morphologies. Such a convergence limits the versatility of chemical control on biomorphogenesis. Contrarily, the strong kinetic effect of silicic acids may make them very efficient controllers of biomorphogenesis, if coupled with a physical shape control, for example, by templates. Thus, silicic acids show a unique bimodality as a controller of calcite biomineralisation and as an abundant biomineral.
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