Structure and mechanical properties of high-porosity macroscopic agglomerates formed by random ballistic deposition

We present experimental results on the mechanical properties of macroscopic agglomerates formed by ballistic hit-and-stick deposition. The agglomerates, produced with a new experimental method, consist of monodisperse SiO2 spheres with 1.5 microm diameter and have a volume filling factor of phi=0.15, matching very closely the theoretical value for random ballistic deposition. They are mechanically stable against unidirectional compression of up to 500 Pa. For pressures above that value, the volume filling factor increases to a maximum of phi=0.33 for pressures above 10(5) Pa. The tensile strength of slightly compressed samples (phi=0.2) is 1000 Pa.