Sol–Gel Transition in Nanodiamond Aqueous Dispersions by Small-Angle Scattering

This paper reports the results of the comparative structural characterization of detonation nanodiamond particles and their aggregates in hydrosols and hydrogels by small-angle scattering (SAS) techniques. The data from different neutron and X-ray (synchrotron radiation) diffractometers cover a wide range of momentum transfer and show multilevel structure organizations at the size scale from 1 to 1000 nm and higher. For this purpose, in addition to the conventional SAS techniques the methods of very small-angle and ultrasmall-angle neutron scattering were applied. The fraction of nanodiamond particles in the aggregates is determined. A complex two-step mechanism of nanodiamond cluster association into a network during the sol–gel transition is revealed. It is assumed that a reason for the reversibility of this process is a different compactness of the corresponding structural levels defined by different fractal organizations.