  In order to control aggregation phenomena in suspensions of nanoparticles,
one often charges the particles electrically, e.g. by triboelectric charging.
Stabilization of suspensions against aggregation of particles is an important
issue, which may be realized by monopolar charging, where particles repel each
other. Contrarily, bipolar charging may be used in coating processes, where
smaller particles of one material coat larger particles of another material.
When the two particle fractions are charged oppositely, aggregation between
equally charged particles is hindered whereas aggregation between oppositely
charged particles is preferred, thereby improving the coating process. We study
various aspects of these two situations by theoretical investigations and
computer simulations.
