103
2.2106 and its effect on the surface charge density, electrokinetic potential, and stability of aqueous suspensions of sil-
icon nitride were studied. The values of PEO adsorption are independent of pH medium in acidic and neutral
media; however, they are significantly lowered upon alkalization. PEO adsorption does not affect the surface
charge, although it tends to decrease the absolute values of the negative
-potential of silicon nitride. Electro-kinetic thicknesses of the adsorbed layer of high-molecular-weight PEO samples correlate well with the sizes
of the tails of adsorbed molecules calculated on the basis of the Scheutjens–Fleer theory. Calculations of the
potential curves of particle interactions demonstrated that in the absence of electrolytes, the stability of all poly-
mer-containing suspensions is determined by the balance between the forces of van der Waals attraction and
electrostatic repulsion. Addition of electrolytes results in that long-range particle interaction being governed
only by the balance between the forces of molecular attraction and sterical repulsion of the tails of adsorbed
polymer, whereas the behavior of suspensions is determined by the polymer molecular weight and the size of
suspension particles. Saturated adsorbed layers of high-molecular-weight PEO samples tend to stabilize the
highly dispersed fraction of a silicon nitride suspension within the entire studied pH range, whereas large par-
ticles tend to aggregate in the secondary minimum by the barrierless mechanism. The behavior of suspensions
in PEO solutions, from which polymer is completely adsorbed, is governed by the balance between the floccu-
lating ability of PEO and the weak protective effect of thin adsorbed layers of a polymer.