where H is the interparticle surface to surface distance, R is The effects of alkyl chain length and concentration of surfactant the radius of the particle or of the curvature for the mica on the yield stress-pH behavior of a 57 wt% ZrO 2 suspension sheet, A and B are proportionality constants, and l 1 and l 2 were evaluated. An alkyl chain length n of between 5 to 12 carbons are characteristic decay lengths of a short-and a long-range was used. For chain length n Β§ 7, a much larger maximum yield component, respectively (9-11). l 1 is on the order of about stress (at zero zeta potential) than that without additive was re-25 A Λand l 2 is about 250 A Λ. The short-range component corded. The increase in the maximum yield stress is as much as was shown to be insensitive to monovalent salt concentration sixfold. Generally, a higher surfactant concentration leads to a (3,4).
higher yield stress. The increase in the maximum yield stress is
The measured SFA force F(H) is related to the free enquite insensitive to surfactant chain length. Ionic strength appears to have no effect on the yield stress-pH behavior of suspensions ergy of interaction per unit area (E f ( H)) via the Derjaguin with a surfactant. The data are consistent with the observation of approximation, a long-range attractive (hydrophobic) force measured in surface force experiments.