Dielectric behaviour of suspensions of non-spherical colloidal particles

In this paper, we explore the possibility of using low-frequency dielectric dispersion (LFDD) measurements in suspensions of non-spherical particles. We present results on the LFDD of clay suspensions, with laminar, non-homog eneously charged particles, and of monodisperse spheroids of haematite (iro n III oxide). The heterogeneous surface of the clay (montmorillonite) is ma nifested in dielectric measurements, since two relaxation times tone associ ated with faces and the other with edges) can be separated. Furthermore, it is found that the latter is absent at pH 7, thereby directly confirming th at the edges of the clay platelets are uncharged at such pH. Experiments co nducted with monodisperse haematite spheroids allow a preliminary check of existing theories for the LFDD in such geometries. Comparison of the zeta p otentials deduced from dielectric and electrophoresis measurements confirm the validity of the models, and suggest that haematite could be a model sph eroidal colloid, to which standard electrokinetic theories are applicable.