Small angle neutron scattering characterization of colloidal and fractal aerogels

Extreme length scales of aerogel structures limit the effectiveness of many characterization techniques. With the resolutions commensurate with the length scales found in these materials, small angle neutron scattering measurements were conducted and interpreted using several models developed for other ceramic systems (polydispersed hard-sphere, fractal, and maximum entropy models). Interference (polydispersed hard-sphere) and maximum entropy models indicate that tetraethoxysilane (TEOS) aerogel structure may be comprised of oblate nanoparticles within oblate mesoparticles. The fractal model was used to describe the structures of triethoxysilane (TES) and trimethoxysilane (TMS) aerogels and to quantify their fractal properties. TES aerogels appear to be networks of volume fractals while TMS aerogels contain both volume and surface fractal elements.