Materials structuration and processing to control morphology and

Materials structuration and processing to control
morphology and functionality
Glenna L. Drisko
Laboratoire de Chimie de la Matière Condensée de Paris, Collége de France
Material properties are derived from composition, structure, crystallinity and
form. Sol-gel chemistry provides the flexibility to tune all of these derivatives,
semi-independently. The composition is controlled by choosing the initial
precursors present in the solution. The pH is adjusted or ligands are used in
order to control the onset of condensation. Structure can be designed using selfassembly, phase separation, reactive ion etching and template chemistry to
control morphology over a range from nanometers to microns. Crystallization can
destroy the mesostructure of a material, however this can be overcome with the
appropriate know-how. Processing is used to produce inorganic and hybrid
materials in the form of beads, films, nanoparticles, xerogels and membranes.
The synthesis of complex hierarchical architectures will be discussed, along with
the role of chemical composition, form and crystallinity and their relationship to
the resultant material properties.
The crystallization of silica films and particles will be discussed in detail,
particularly the formation of structured epitaxial α-quartz films on silicon
substrates. These films have been produced using cations (Ca2+, Sr2+ and Ba2+) as
crystallization catalysts, which induce homogenous nucleation throughout the
film. Mesopores as small as 20 nm could be maintained in the crystalline film.
These materials demonstrate piezoelectricity and therefore may find application
in microelectronic devices.
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