Introducing a desired solid guest to nn about-to-gel silica sol prevents I
complete encapsulation of the guest particles by the silica, such that the
composite retains the bulk and surface properties of each component on the
nanoscale. The transport- and density-dependent properties of the composite
aerogel call be tuned by varying the volume fraction of the second solid,
thereby increasing the design flexibility of these nanoscale materials for
optical, chemical, thermal, magnetic, and electronic applications. The chem
ical and physical properties of the composite material can be further engin
eered at multiple points during sol-gel processing by modifying the host so
lid the guest solid, the composite gel, or the composite aerogel.