Three-dimensional structure of precipitated silica as determined by electron tomography

The three-dimensional structure of silica VN3 has been determined using electron tomography. A detailed investigation of a typical cluster is shown. The cluster is a sparsely packed, almost spherical symmetric object with a diameter of about 130 nm. Its basic units are primary particles, which are more or less spherical symmetric, with an average diameter of about 15 nm. A simple interpretation in terms of a model based on the theory of fractals reveals a mass fractal dimension of about 1.7 which coincides with the results of scattering experiments.