A process for the production of a suspension of crystalline and/or densified, surface-modified nanoscale particles in a dispersant. The process comprises: (a) heat-treating a suspension of amorphous or semicrystalline, non-surface-modified nanoscale particles in a first dispersant to obtain crystallized and/or densified particles; and (b) mechanically activating, in the presence of at least one modifying agent, the particles obtained according to (a) as a suspension in the first dispersant or in a different dispersant to obtain a suspension of crystalline and/or densified nanoscale particles which are surface-modified by the at least one modifying agent.